Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1363 insertions, 0 deletions

diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
new file mode 100644
index 000000000..2a99ffb61
--- /dev/null
+++ b/drivers/mmc/host/mmc_spi.c
@@ -0,0 +1,1363 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Access SD/MMC cards through SPI master controllers
+ *
+ * (C) Copyright 2005, Intec Automation,
+ *		Mike Lavender (mike@steroidmicros)
+ * (C) Copyright 2006-2007, David Brownell
+ * (C) Copyright 2007, Axis Communications,
+ *		Hans-Peter Nilsson (hp@axis.com)
+ * (C) Copyright 2007, ATRON electronic GmbH,
+ *		Jan Nikitenko <jan.nikitenko@gmail.com>
+ */
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/bio.h>
+#include <linux/dma-direction.h>
+#include <linux/crc7.h>
+#include <linux/crc-itu-t.h>
+#include <linux/scatterlist.h>
+
+#include <linux/mmc/host.h>
+#include <linux/mmc/mmc.h>		/* for R1_SPI_* bit values */
+#include <linux/mmc/slot-gpio.h>
+
+#include <linux/spi/spi.h>
+#include <linux/spi/mmc_spi.h>
+
+#include <asm/unaligned.h>
+
+
+/* NOTES:
+ *
+ * - For now, we won't try to interoperate with a real mmc/sd/sdio
+ *   controller, although some of them do have hardware support for
+ *   SPI protocol.  The main reason for such configs would be mmc-ish
+ *   cards like DataFlash, which don't support that "native" protocol.
+ *
+ *   We don't have a "DataFlash/MMC/SD/SDIO card slot" abstraction to
+ *   switch between driver stacks, and in any case if "native" mode
+ *   is available, it will be faster and hence preferable.
+ *
+ * - MMC depends on a different chipselect management policy than the
+ *   SPI interface currently supports for shared bus segments:  it needs
+ *   to issue multiple spi_message requests with the chipselect active,
+ *   using the results of one message to decide the next one to issue.
+ *
+ *   Pending updates to the programming interface, this driver expects
+ *   that it not share the bus with other drivers (precluding conflicts).
+ *
+ * - We tell the controller to keep the chipselect active from the
+ *   beginning of an mmc_host_ops.request until the end.  So beware
+ *   of SPI controller drivers that mis-handle the cs_change flag!
+ *
+ *   However, many cards seem OK with chipselect flapping up/down
+ *   during that time ... at least on unshared bus segments.
+ */
+
+
+/*
+ * Local protocol constants, internal to data block protocols.
+ */
+
+/* Response tokens used to ack each block written: */
+#define SPI_MMC_RESPONSE_CODE(x)	((x) & 0x1f)
+#define SPI_RESPONSE_ACCEPTED		((2 << 1)|1)
+#define SPI_RESPONSE_CRC_ERR		((5 << 1)|1)
+#define SPI_RESPONSE_WRITE_ERR		((6 << 1)|1)
+
+/* Read and write blocks start with these tokens and end with crc;
+ * on error, read tokens act like a subset of R2_SPI_* values.
+ */
+#define SPI_TOKEN_SINGLE	0xfe	/* single block r/w, multiblock read */
+#define SPI_TOKEN_MULTI_WRITE	0xfc	/* multiblock write */
+#define SPI_TOKEN_STOP_TRAN	0xfd	/* terminate multiblock write */
+
+#define MMC_SPI_BLOCKSIZE	512
+
+#define MMC_SPI_R1B_TIMEOUT_MS	3000
+#define MMC_SPI_INIT_TIMEOUT_MS	3000
+
+/* One of the critical speed parameters is the amount of data which may
+ * be transferred in one command. If this value is too low, the SD card
+ * controller has to do multiple partial block writes (argggh!). With
+ * today (2008) SD cards there is little speed gain if we transfer more
+ * than 64 KBytes at a time. So use this value until there is any indication
+ * that we should do more here.
+ */
+#define MMC_SPI_BLOCKSATONCE	128
+
+/****************************************************************************/
+
+/*
+ * Local Data Structures
+ */
+
+/* "scratch" is per-{command,block} data exchanged with the card */
+struct scratch {
+	u8			status[29];
+	u8			data_token;
+	__be16			crc_val;
+};
+
+struct mmc_spi_host {
+	struct mmc_host		*mmc;
+	struct spi_device	*spi;
+
+	unsigned char		power_mode;
+	u16			powerup_msecs;
+
+	struct mmc_spi_platform_data	*pdata;
+
+	/* for bulk data transfers */
+	struct spi_transfer	token, t, crc, early_status;
+	struct spi_message	m;
+
+	/* for status readback */
+	struct spi_transfer	status;
+	struct spi_message	readback;
+
+	/* buffer used for commands and for message "overhead" */
+	struct scratch		*data;
+
+	/* Specs say to write ones most of the time, even when the card
+	 * has no need to read its input data; and many cards won't care.
+	 * This is our source of those ones.
+	 */
+	void			*ones;
+};
+
+
+/****************************************************************************/
+
+/*
+ * MMC-over-SPI protocol glue, used by the MMC stack interface
+ */
+
+static inline int mmc_cs_off(struct mmc_spi_host *host)
+{
+	/* chipselect will always be inactive after setup() */
+	return spi_setup(host->spi);
+}
+
+static int mmc_spi_readbytes(struct mmc_spi_host *host, unsigned int len)
+{
+	if (len > sizeof(*host->data)) {
+		WARN_ON(1);
+		return -EIO;
+	}
+
+	host->status.len = len;
+
+	return spi_sync_locked(host->spi, &host->readback);
+}
+
+static int mmc_spi_skip(struct mmc_spi_host *host, unsigned long timeout,
+			unsigned n, u8 byte)
+{
+	u8 *cp = host->data->status;
+	unsigned long start = jiffies;
+
+	do {
+		int		status;
+		unsigned	i;
+
+		status = mmc_spi_readbytes(host, n);
+		if (status < 0)
+			return status;
+
+		for (i = 0; i < n; i++) {
+			if (cp[i] != byte)
+				return cp[i];
+		}
+
+		/* If we need long timeouts, we may release the CPU */
+		cond_resched();
+	} while (time_is_after_jiffies(start + timeout));
+	return -ETIMEDOUT;
+}
+
+static inline int
+mmc_spi_wait_unbusy(struct mmc_spi_host *host, unsigned long timeout)
+{
+	return mmc_spi_skip(host, timeout, sizeof(host->data->status), 0);
+}
+
+static int mmc_spi_readtoken(struct mmc_spi_host *host, unsigned long timeout)
+{
+	return mmc_spi_skip(host, timeout, 1, 0xff);
+}
+
+
+/*
+ * Note that for SPI, cmd->resp[0] is not the same data as "native" protocol
+ * hosts return!  The low byte holds R1_SPI bits.  The next byte may hold
+ * R2_SPI bits ... for SEND_STATUS, or after data read errors.
+ *
+ * cmd->resp[1] holds any four-byte response, for R3 (READ_OCR) and on
+ * newer cards R7 (IF_COND).
+ */
+
+static char *maptype(struct mmc_command *cmd)
+{
+	switch (mmc_spi_resp_type(cmd)) {
+	case MMC_RSP_SPI_R1:	return "R1";
+	case MMC_RSP_SPI_R1B:	return "R1B";
+	case MMC_RSP_SPI_R2:	return "R2/R5";
+	case MMC_RSP_SPI_R3:	return "R3/R4/R7";
+	default:		return "?";
+	}
+}
+
+/* return zero, else negative errno after setting cmd->error */
+static int mmc_spi_response_get(struct mmc_spi_host *host,
+		struct mmc_command *cmd, int cs_on)
+{
+	unsigned long timeout_ms;
+	u8	*cp = host->data->status;
+	u8	*end = cp + host->t.len;
+	int	value = 0;
+	int	bitshift;
+	u8 	leftover = 0;
+	unsigned short rotator;
+	int 	i;
+	char	tag[32];
+
+	snprintf(tag, sizeof(tag), "  ... CMD%d response SPI_%s",
+		cmd->opcode, maptype(cmd));
+
+	/* Except for data block reads, the whole response will already
+	 * be stored in the scratch buffer.  It's somewhere after the
+	 * command and the first byte we read after it.  We ignore that
+	 * first byte.  After STOP_TRANSMISSION command it may include
+	 * two data bits, but otherwise it's all ones.
+	 */
+	cp += 8;
+	while (cp < end && *cp == 0xff)
+		cp++;
+
+	/* Data block reads (R1 response types) may need more data... */
+	if (cp == end) {
+		cp = host->data->status;
+		end = cp+1;
+
+		/* Card sends N(CR) (== 1..8) bytes of all-ones then one
+		 * status byte ... and we already scanned 2 bytes.
+		 *
+		 * REVISIT block read paths use nasty byte-at-a-time I/O
+		 * so it can always DMA directly into the target buffer.
+		 * It'd probably be better to memcpy() the first chunk and
+		 * avoid extra i/o calls...
+		 *
+		 * Note we check for more than 8 bytes, because in practice,
+		 * some SD cards are slow...
+		 */
+		for (i = 2; i < 16; i++) {
+			value = mmc_spi_readbytes(host, 1);
+			if (value < 0)
+				goto done;
+			if (*cp != 0xff)
+				goto checkstatus;
+		}
+		value = -ETIMEDOUT;
+		goto done;
+	}
+
+checkstatus:
+	bitshift = 0;
+	if (*cp & 0x80)	{
+		/* Houston, we have an ugly card with a bit-shifted response */
+		rotator = *cp++ << 8;
+		/* read the next byte */
+		if (cp == end) {
+			value = mmc_spi_readbytes(host, 1);
+			if (value < 0)
+				goto done;
+			cp = host->data->status;
+			end = cp+1;
+		}
+		rotator |= *cp++;
+		while (rotator & 0x8000) {
+			bitshift++;
+			rotator <<= 1;
+		}
+		cmd->resp[0] = rotator >> 8;
+		leftover = rotator;
+	} else {
+		cmd->resp[0] = *cp++;
+	}
+	cmd->error = 0;
+
+	/* Status byte: the entire seven-bit R1 response.  */
+	if (cmd->resp[0] != 0) {
+		if ((R1_SPI_PARAMETER | R1_SPI_ADDRESS)
+				& cmd->resp[0])
+			value = -EFAULT; /* Bad address */
+		else if (R1_SPI_ILLEGAL_COMMAND & cmd->resp[0])
+			value = -ENOSYS; /* Function not implemented */
+		else if (R1_SPI_COM_CRC & cmd->resp[0])
+			value = -EILSEQ; /* Illegal byte sequence */
+		else if ((R1_SPI_ERASE_SEQ | R1_SPI_ERASE_RESET)
+				& cmd->resp[0])
+			value = -EIO;    /* I/O error */
+		/* else R1_SPI_IDLE, "it's resetting" */
+	}
+
+	switch (mmc_spi_resp_type(cmd)) {
+
+	/* SPI R1B == R1 + busy; STOP_TRANSMISSION (for multiblock reads)
+	 * and less-common stuff like various erase operations.
+	 */
+	case MMC_RSP_SPI_R1B:
+		/* maybe we read all the busy tokens already */
+		while (cp < end && *cp == 0)
+			cp++;
+		if (cp == end) {
+			timeout_ms = cmd->busy_timeout ? cmd->busy_timeout :
+				MMC_SPI_R1B_TIMEOUT_MS;
+			mmc_spi_wait_unbusy(host, msecs_to_jiffies(timeout_ms));
+		}
+		break;
+
+	/* SPI R2 == R1 + second status byte; SEND_STATUS
+	 * SPI R5 == R1 + data byte; IO_RW_DIRECT
+	 */
+	case MMC_RSP_SPI_R2:
+		/* read the next byte */
+		if (cp == end) {
+			value = mmc_spi_readbytes(host, 1);
+			if (value < 0)
+				goto done;
+			cp = host->data->status;
+			end = cp+1;
+		}
+		if (bitshift) {
+			rotator = leftover << 8;
+			rotator |= *cp << bitshift;
+			cmd->resp[0] |= (rotator & 0xFF00);
+		} else {
+			cmd->resp[0] |= *cp << 8;
+		}
+		break;
+
+	/* SPI R3, R4, or R7 == R1 + 4 bytes */
+	case MMC_RSP_SPI_R3:
+		rotator = leftover << 8;
+		cmd->resp[1] = 0;
+		for (i = 0; i < 4; i++) {
+			cmd->resp[1] <<= 8;
+			/* read the next byte */
+			if (cp == end) {
+				value = mmc_spi_readbytes(host, 1);
+				if (value < 0)
+					goto done;
+				cp = host->data->status;
+				end = cp+1;
+			}
+			if (bitshift) {
+				rotator |= *cp++ << bitshift;
+				cmd->resp[1] |= (rotator >> 8);
+				rotator <<= 8;
+			} else {
+				cmd->resp[1] |= *cp++;
+			}
+		}
+		break;
+
+	/* SPI R1 == just one status byte */
+	case MMC_RSP_SPI_R1:
+		break;
+
+	default:
+		dev_dbg(&host->spi->dev, "bad response type %04x\n",
+			mmc_spi_resp_type(cmd));
+		if (value >= 0)
+			value = -EINVAL;
+		goto done;
+	}
+
+	if (value < 0)
+		dev_dbg(&host->spi->dev, "%s: resp %04x %08x\n",
+			tag, cmd->resp[0], cmd->resp[1]);
+
+	/* disable chipselect on errors and some success cases */
+	if (value >= 0 && cs_on)
+		return value;
+done:
+	if (value < 0)
+		cmd->error = value;
+	mmc_cs_off(host);
+	return value;
+}
+
+/* Issue command and read its response.
+ * Returns zero on success, negative for error.
+ *
+ * On error, caller must cope with mmc core retry mechanism.  That
+ * means immediate low-level resubmit, which affects the bus lock...
+ */
+static int
+mmc_spi_command_send(struct mmc_spi_host *host,
+		struct mmc_request *mrq,
+		struct mmc_command *cmd, int cs_on)
+{
+	struct scratch		*data = host->data;
+	u8			*cp = data->status;
+	int			status;
+	struct spi_transfer	*t;
+
+	/* We can handle most commands (except block reads) in one full
+	 * duplex I/O operation before either starting the next transfer
+	 * (data block or command) or else deselecting the card.
+	 *
+	 * First, write 7 bytes:
+	 *  - an all-ones byte to ensure the card is ready
+	 *  - opcode byte (plus start and transmission bits)
+	 *  - four bytes of big-endian argument
+	 *  - crc7 (plus end bit) ... always computed, it's cheap
+	 *
+	 * We init the whole buffer to all-ones, which is what we need
+	 * to write while we're reading (later) response data.
+	 */
+	memset(cp, 0xff, sizeof(data->status));
+
+	cp[1] = 0x40 | cmd->opcode;
+	put_unaligned_be32(cmd->arg, cp + 2);
+	cp[6] = crc7_be(0, cp + 1, 5) | 0x01;
+	cp += 7;
+
+	/* Then, read up to 13 bytes (while writing all-ones):
+	 *  - N(CR) (== 1..8) bytes of all-ones
+	 *  - status byte (for all response types)
+	 *  - the rest of the response, either:
+	 *      + nothing, for R1 or R1B responses
+	 *	+ second status byte, for R2 responses
+	 *	+ four data bytes, for R3 and R7 responses
+	 *
+	 * Finally, read some more bytes ... in the nice cases we know in
+	 * advance how many, and reading 1 more is always OK:
+	 *  - N(EC) (== 0..N) bytes of all-ones, before deselect/finish
+	 *  - N(RC) (== 1..N) bytes of all-ones, before next command
+	 *  - N(WR) (== 1..N) bytes of all-ones, before data write
+	 *
+	 * So in those cases one full duplex I/O of at most 21 bytes will
+	 * handle the whole command, leaving the card ready to receive a
+	 * data block or new command.  We do that whenever we can, shaving
+	 * CPU and IRQ costs (especially when using DMA or FIFOs).
+	 *
+	 * There are two other cases, where it's not generally practical
+	 * to rely on a single I/O:
+	 *
+	 *  - R1B responses need at least N(EC) bytes of all-zeroes.
+	 *
+	 *    In this case we can *try* to fit it into one I/O, then
+	 *    maybe read more data later.
+	 *
+	 *  - Data block reads are more troublesome, since a variable
+	 *    number of padding bytes precede the token and data.
+	 *      + N(CX) (== 0..8) bytes of all-ones, before CSD or CID
+	 *      + N(AC) (== 1..many) bytes of all-ones
+	 *
+	 *    In this case we currently only have minimal speedups here:
+	 *    when N(CR) == 1 we can avoid I/O in response_get().
+	 */
+	if (cs_on && (mrq->data->flags & MMC_DATA_READ)) {
+		cp += 2;	/* min(N(CR)) + status */
+		/* R1 */
+	} else {
+		cp += 10;	/* max(N(CR)) + status + min(N(RC),N(WR)) */
+		if (cmd->flags & MMC_RSP_SPI_S2)	/* R2/R5 */
+			cp++;
+		else if (cmd->flags & MMC_RSP_SPI_B4)	/* R3/R4/R7 */
+			cp += 4;
+		else if (cmd->flags & MMC_RSP_BUSY)	/* R1B */
+			cp = data->status + sizeof(data->status);
+		/* else:  R1 (most commands) */
+	}
+
+	dev_dbg(&host->spi->dev, "  CMD%d, resp %s\n",
+		cmd->opcode, maptype(cmd));
+
+	/* send command, leaving chipselect active */
+	spi_message_init(&host->m);
+
+	t = &host->t;
+	memset(t, 0, sizeof(*t));
+	t->tx_buf = t->rx_buf = data->status;
+	t->len = cp - data->status;
+	t->cs_change = 1;
+	spi_message_add_tail(t, &host->m);
+
+	status = spi_sync_locked(host->spi, &host->m);
+	if (status < 0) {
+		dev_dbg(&host->spi->dev, "  ... write returned %d\n", status);
+		cmd->error = status;
+		return status;
+	}
+
+	/* after no-data commands and STOP_TRANSMISSION, chipselect off */
+	return mmc_spi_response_get(host, cmd, cs_on);
+}
+
+/* Build data message with up to four separate transfers.  For TX, we
+ * start by writing the data token.  And in most cases, we finish with
+ * a status transfer.
+ *
+ * We always provide TX data for data and CRC.  The MMC/SD protocol
+ * requires us to write ones; but Linux defaults to writing zeroes;
+ * so we explicitly initialize it to all ones on RX paths.
+ */
+static void
+mmc_spi_setup_data_message(
+	struct mmc_spi_host	*host,
+	bool			multiple,
+	enum dma_data_direction	direction)
+{
+	struct spi_transfer	*t;
+	struct scratch		*scratch = host->data;
+
+	spi_message_init(&host->m);
+
+	/* for reads, readblock() skips 0xff bytes before finding
+	 * the token; for writes, this transfer issues that token.
+	 */
+	if (direction == DMA_TO_DEVICE) {
+		t = &host->token;
+		memset(t, 0, sizeof(*t));
+		t->len = 1;
+		if (multiple)
+			scratch->data_token = SPI_TOKEN_MULTI_WRITE;
+		else
+			scratch->data_token = SPI_TOKEN_SINGLE;
+		t->tx_buf = &scratch->data_token;
+		spi_message_add_tail(t, &host->m);
+	}
+
+	/* Body of transfer is buffer, then CRC ...
+	 * either TX-only, or RX with TX-ones.
+	 */
+	t = &host->t;
+	memset(t, 0, sizeof(*t));
+	t->tx_buf = host->ones;
+	/* length and actual buffer info are written later */
+	spi_message_add_tail(t, &host->m);
+
+	t = &host->crc;
+	memset(t, 0, sizeof(*t));
+	t->len = 2;
+	if (direction == DMA_TO_DEVICE) {
+		/* the actual CRC may get written later */
+		t->tx_buf = &scratch->crc_val;
+	} else {
+		t->tx_buf = host->ones;
+		t->rx_buf = &scratch->crc_val;
+	}
+	spi_message_add_tail(t, &host->m);
+
+	/*
+	 * A single block read is followed by N(EC) [0+] all-ones bytes
+	 * before deselect ... don't bother.
+	 *
+	 * Multiblock reads are followed by N(AC) [1+] all-ones bytes before
+	 * the next block is read, or a STOP_TRANSMISSION is issued.  We'll
+	 * collect that single byte, so readblock() doesn't need to.
+	 *
+	 * For a write, the one-byte data response follows immediately, then
+	 * come zero or more busy bytes, then N(WR) [1+] all-ones bytes.
+	 * Then single block reads may deselect, and multiblock ones issue
+	 * the next token (next data block, or STOP_TRAN).  We can try to
+	 * minimize I/O ops by using a single read to collect end-of-busy.
+	 */
+	if (multiple || direction == DMA_TO_DEVICE) {
+		t = &host->early_status;
+		memset(t, 0, sizeof(*t));
+		t->len = (direction == DMA_TO_DEVICE) ? sizeof(scratch->status) : 1;
+		t->tx_buf = host->ones;
+		t->rx_buf = scratch->status;
+		t->cs_change = 1;
+		spi_message_add_tail(t, &host->m);
+	}
+}
+
+/*
+ * Write one block:
+ *  - caller handled preceding N(WR) [1+] all-ones bytes
+ *  - data block
+ *	+ token
+ *	+ data bytes
+ *	+ crc16
+ *  - an all-ones byte ... card writes a data-response byte
+ *  - followed by N(EC) [0+] all-ones bytes, card writes zero/'busy'
+ *
+ * Return negative errno, else success.
+ */
+static int
+mmc_spi_writeblock(struct mmc_spi_host *host, struct spi_transfer *t,
+	unsigned long timeout)
+{
+	struct spi_device	*spi = host->spi;
+	int			status, i;
+	struct scratch		*scratch = host->data;
+	u32			pattern;
+
+	if (host->mmc->use_spi_crc)
+		scratch->crc_val = cpu_to_be16(crc_itu_t(0, t->tx_buf, t->len));
+
+	status = spi_sync_locked(spi, &host->m);
+	if (status != 0) {
+		dev_dbg(&spi->dev, "write error (%d)\n", status);
+		return status;
+	}
+
+	/*
+	 * Get the transmission data-response reply.  It must follow
+	 * immediately after the data block we transferred.  This reply
+	 * doesn't necessarily tell whether the write operation succeeded;
+	 * it just says if the transmission was ok and whether *earlier*
+	 * writes succeeded; see the standard.
+	 *
+	 * In practice, there are (even modern SDHC-)cards which are late
+	 * in sending the response, and miss the time frame by a few bits,
+	 * so we have to cope with this situation and check the response
+	 * bit-by-bit. Arggh!!!
+	 */
+	pattern = get_unaligned_be32(scratch->status);
+
+	/* First 3 bit of pattern are undefined */
+	pattern |= 0xE0000000;
+
+	/* left-adjust to leading 0 bit */
+	while (pattern & 0x80000000)
+		pattern <<= 1;
+	/* right-adjust for pattern matching. Code is in bit 4..0 now. */
+	pattern >>= 27;
+
+	switch (pattern) {
+	case SPI_RESPONSE_ACCEPTED:
+		status = 0;
+		break;
+	case SPI_RESPONSE_CRC_ERR:
+		/* host shall then issue MMC_STOP_TRANSMISSION */
+		status = -EILSEQ;
+		break;
+	case SPI_RESPONSE_WRITE_ERR:
+		/* host shall then issue MMC_STOP_TRANSMISSION,
+		 * and should MMC_SEND_STATUS to sort it out
+		 */
+		status = -EIO;
+		break;
+	default:
+		status = -EPROTO;
+		break;
+	}
+	if (status != 0) {
+		dev_dbg(&spi->dev, "write error %02x (%d)\n",
+			scratch->status[0], status);
+		return status;
+	}
+
+	t->tx_buf += t->len;
+
+	/* Return when not busy.  If we didn't collect that status yet,
+	 * we'll need some more I/O.
+	 */
+	for (i = 4; i < sizeof(scratch->status); i++) {
+		/* card is non-busy if the most recent bit is 1 */
+		if (scratch->status[i] & 0x01)
+			return 0;
+	}
+	return mmc_spi_wait_unbusy(host, timeout);
+}
+
+/*
+ * Read one block:
+ *  - skip leading all-ones bytes ... either
+ *      + N(AC) [1..f(clock,CSD)] usually, else
+ *      + N(CX) [0..8] when reading CSD or CID
+ *  - data block
+ *	+ token ... if error token, no data or crc
+ *	+ data bytes
+ *	+ crc16
+ *
+ * After single block reads, we're done; N(EC) [0+] all-ones bytes follow
+ * before dropping chipselect.
+ *
+ * For multiblock reads, caller either reads the next block or issues a
+ * STOP_TRANSMISSION command.
+ */
+static int
+mmc_spi_readblock(struct mmc_spi_host *host, struct spi_transfer *t,
+	unsigned long timeout)
+{
+	struct spi_device	*spi = host->spi;
+	int			status;
+	struct scratch		*scratch = host->data;
+	unsigned int 		bitshift;
+	u8			leftover;
+
+	/* At least one SD card sends an all-zeroes byte when N(CX)
+	 * applies, before the all-ones bytes ... just cope with that.
+	 */
+	status = mmc_spi_readbytes(host, 1);
+	if (status < 0)
+		return status;
+	status = scratch->status[0];
+	if (status == 0xff || status == 0)
+		status = mmc_spi_readtoken(host, timeout);
+
+	if (status < 0) {
+		dev_dbg(&spi->dev, "read error %02x (%d)\n", status, status);
+		return status;
+	}
+
+	/* The token may be bit-shifted...
+	 * the first 0-bit precedes the data stream.
+	 */
+	bitshift = 7;
+	while (status & 0x80) {
+		status <<= 1;
+		bitshift--;
+	}
+	leftover = status << 1;
+
+	status = spi_sync_locked(spi, &host->m);
+	if (status < 0) {
+		dev_dbg(&spi->dev, "read error %d\n", status);
+		return status;
+	}
+
+	if (bitshift) {
+		/* Walk through the data and the crc and do
+		 * all the magic to get byte-aligned data.
+		 */
+		u8 *cp = t->rx_buf;
+		unsigned int len;
+		unsigned int bitright = 8 - bitshift;
+		u8 temp;
+		for (len = t->len; len; len--) {
+			temp = *cp;
+			*cp++ = leftover | (temp >> bitshift);
+			leftover = temp << bitright;
+		}
+		cp = (u8 *) &scratch->crc_val;
+		temp = *cp;
+		*cp++ = leftover | (temp >> bitshift);
+		leftover = temp << bitright;
+		temp = *cp;
+		*cp = leftover | (temp >> bitshift);
+	}
+
+	if (host->mmc->use_spi_crc) {
+		u16 crc = crc_itu_t(0, t->rx_buf, t->len);
+
+		be16_to_cpus(&scratch->crc_val);
+		if (scratch->crc_val != crc) {
+			dev_dbg(&spi->dev,
+				"read - crc error: crc_val=0x%04x, computed=0x%04x len=%d\n",
+				scratch->crc_val, crc, t->len);
+			return -EILSEQ;
+		}
+	}
+
+	t->rx_buf += t->len;
+
+	return 0;
+}
+
+/*
+ * An MMC/SD data stage includes one or more blocks, optional CRCs,
+ * and inline handshaking.  That handhaking makes it unlike most
+ * other SPI protocol stacks.
+ */
+static void
+mmc_spi_data_do(struct mmc_spi_host *host, struct mmc_command *cmd,
+		struct mmc_data *data, u32 blk_size)
+{
+	struct spi_device	*spi = host->spi;
+	struct spi_transfer	*t;
+	enum dma_data_direction	direction = mmc_get_dma_dir(data);
+	struct scatterlist	*sg;
+	unsigned		n_sg;
+	bool			multiple = (data->blocks > 1);
+	const char		*write_or_read = (direction == DMA_TO_DEVICE) ? "write" : "read";
+	u32			clock_rate;
+	unsigned long		timeout;
+
+	mmc_spi_setup_data_message(host, multiple, direction);
+	t = &host->t;
+
+	if (t->speed_hz)
+		clock_rate = t->speed_hz;
+	else
+		clock_rate = spi->max_speed_hz;
+
+	timeout = data->timeout_ns / 1000 +
+		  data->timeout_clks * 1000000 / clock_rate;
+	timeout = usecs_to_jiffies((unsigned int)timeout) + 1;
+
+	/* Handle scatterlist segments one at a time, with synch for
+	 * each 512-byte block
+	 */
+	for_each_sg(data->sg, sg, data->sg_len, n_sg) {
+		int			status = 0;
+		void			*kmap_addr;
+		unsigned		length = sg->length;
+
+		/* allow pio too; we don't allow highmem */
+		kmap_addr = kmap(sg_page(sg));
+		if (direction == DMA_TO_DEVICE)
+			t->tx_buf = kmap_addr + sg->offset;
+		else
+			t->rx_buf = kmap_addr + sg->offset;
+
+		/* transfer each block, and update request status */
+		while (length) {
+			t->len = min(length, blk_size);
+
+			dev_dbg(&spi->dev, "    %s block, %d bytes\n", write_or_read, t->len);
+
+			if (direction == DMA_TO_DEVICE)
+				status = mmc_spi_writeblock(host, t, timeout);
+			else
+				status = mmc_spi_readblock(host, t, timeout);
+			if (status < 0)
+				break;
+
+			data->bytes_xfered += t->len;
+			length -= t->len;
+
+			if (!multiple)
+				break;
+		}
+
+		/* discard mappings */
+		if (direction == DMA_FROM_DEVICE)
+			flush_dcache_page(sg_page(sg));
+		kunmap(sg_page(sg));
+
+		if (status < 0) {
+			data->error = status;
+			dev_dbg(&spi->dev, "%s status %d\n", write_or_read, status);
+			break;
+		}
+	}
+
+	/* NOTE some docs describe an MMC-only SET_BLOCK_COUNT (CMD23) that
+	 * can be issued before multiblock writes.  Unlike its more widely
+	 * documented analogue for SD cards (SET_WR_BLK_ERASE_COUNT, ACMD23),
+	 * that can affect the STOP_TRAN logic.   Complete (and current)
+	 * MMC specs should sort that out before Linux starts using CMD23.
+	 */
+	if (direction == DMA_TO_DEVICE && multiple) {
+		struct scratch	*scratch = host->data;
+		int		tmp;
+		const unsigned	statlen = sizeof(scratch->status);
+
+		dev_dbg(&spi->dev, "    STOP_TRAN\n");
+
+		/* Tweak the per-block message we set up earlier by morphing
+		 * it to hold single buffer with the token followed by some
+		 * all-ones bytes ... skip N(BR) (0..1), scan the rest for
+		 * "not busy any longer" status, and leave chip selected.
+		 */
+		INIT_LIST_HEAD(&host->m.transfers);
+		list_add(&host->early_status.transfer_list,
+				&host->m.transfers);
+
+		memset(scratch->status, 0xff, statlen);
+		scratch->status[0] = SPI_TOKEN_STOP_TRAN;
+
+		host->early_status.tx_buf = host->early_status.rx_buf;
+		host->early_status.len = statlen;
+
+		tmp = spi_sync_locked(spi, &host->m);
+		if (tmp < 0) {
+			if (!data->error)
+				data->error = tmp;
+			return;
+		}
+
+		/* Ideally we collected "not busy" status with one I/O,
+		 * avoiding wasteful byte-at-a-time scanning... but more
+		 * I/O is often needed.
+		 */
+		for (tmp = 2; tmp < statlen; tmp++) {
+			if (scratch->status[tmp] != 0)
+				return;
+		}
+		tmp = mmc_spi_wait_unbusy(host, timeout);
+		if (tmp < 0 && !data->error)
+			data->error = tmp;
+	}
+}
+
+/****************************************************************************/
+
+/*
+ * MMC driver implementation -- the interface to the MMC stack
+ */
+
+static void mmc_spi_request(struct mmc_host *mmc, struct mmc_request *mrq)
+{
+	struct mmc_spi_host	*host = mmc_priv(mmc);
+	int			status = -EINVAL;
+	int			crc_retry = 5;
+	struct mmc_command	stop;
+
+#ifdef DEBUG
+	/* MMC core and layered drivers *MUST* issue SPI-aware commands */
+	{
+		struct mmc_command	*cmd;
+		int			invalid = 0;
+
+		cmd = mrq->cmd;
+		if (!mmc_spi_resp_type(cmd)) {
+			dev_dbg(&host->spi->dev, "bogus command\n");
+			cmd->error = -EINVAL;
+			invalid = 1;
+		}
+
+		cmd = mrq->stop;
+		if (cmd && !mmc_spi_resp_type(cmd)) {
+			dev_dbg(&host->spi->dev, "bogus STOP command\n");
+			cmd->error = -EINVAL;
+			invalid = 1;
+		}
+
+		if (invalid) {
+			dump_stack();
+			mmc_request_done(host->mmc, mrq);
+			return;
+		}
+	}
+#endif
+
+	/* request exclusive bus access */
+	spi_bus_lock(host->spi->master);
+
+crc_recover:
+	/* issue command; then optionally data and stop */
+	status = mmc_spi_command_send(host, mrq, mrq->cmd, mrq->data != NULL);
+	if (status == 0 && mrq->data) {
+		mmc_spi_data_do(host, mrq->cmd, mrq->data, mrq->data->blksz);
+
+		/*
+		 * The SPI bus is not always reliable for large data transfers.
+		 * If an occasional crc error is reported by the SD device with
+		 * data read/write over SPI, it may be recovered by repeating
+		 * the last SD command again. The retry count is set to 5 to
+		 * ensure the driver passes stress tests.
+		 */
+		if (mrq->data->error == -EILSEQ && crc_retry) {
+			stop.opcode = MMC_STOP_TRANSMISSION;
+			stop.arg = 0;
+			stop.flags = MMC_RSP_SPI_R1B | MMC_RSP_R1B | MMC_CMD_AC;
+			status = mmc_spi_command_send(host, mrq, &stop, 0);
+			crc_retry--;
+			mrq->data->error = 0;
+			goto crc_recover;
+		}
+
+		if (mrq->stop)
+			status = mmc_spi_command_send(host, mrq, mrq->stop, 0);
+		else
+			mmc_cs_off(host);
+	}
+
+	/* release the bus */
+	spi_bus_unlock(host->spi->master);
+
+	mmc_request_done(host->mmc, mrq);
+}
+
+/* See Section 6.4.1, in SD "Simplified Physical Layer Specification 2.0"
+ *
+ * NOTE that here we can't know that the card has just been powered up;
+ * not all MMC/SD sockets support power switching.
+ *
+ * FIXME when the card is still in SPI mode, e.g. from a previous kernel,
+ * this doesn't seem to do the right thing at all...
+ */
+static void mmc_spi_initsequence(struct mmc_spi_host *host)
+{
+	/* Try to be very sure any previous command has completed;
+	 * wait till not-busy, skip debris from any old commands.
+	 */
+	mmc_spi_wait_unbusy(host, msecs_to_jiffies(MMC_SPI_INIT_TIMEOUT_MS));
+	mmc_spi_readbytes(host, 10);
+
+	/*
+	 * Do a burst with chipselect active-high.  We need to do this to
+	 * meet the requirement of 74 clock cycles with both chipselect
+	 * and CMD (MOSI) high before CMD0 ... after the card has been
+	 * powered up to Vdd(min), and so is ready to take commands.
+	 *
+	 * Some cards are particularly needy of this (e.g. Viking "SD256")
+	 * while most others don't seem to care.
+	 *
+	 * Note that this is one of the places MMC/SD plays games with the
+	 * SPI protocol.  Another is that when chipselect is released while
+	 * the card returns BUSY status, the clock must issue several cycles
+	 * with chipselect high before the card will stop driving its output.
+	 *
+	 * SPI_CS_HIGH means "asserted" here. In some cases like when using
+	 * GPIOs for chip select, SPI_CS_HIGH is set but this will be logically
+	 * inverted by gpiolib, so if we want to ascertain to drive it high
+	 * we should toggle the default with an XOR as we do here.
+	 */
+	host->spi->mode ^= SPI_CS_HIGH;
+	if (spi_setup(host->spi) != 0) {
+		/* Just warn; most cards work without it. */
+		dev_warn(&host->spi->dev,
+				"can't change chip-select polarity\n");
+		host->spi->mode ^= SPI_CS_HIGH;
+	} else {
+		mmc_spi_readbytes(host, 18);
+
+		host->spi->mode ^= SPI_CS_HIGH;
+		if (spi_setup(host->spi) != 0) {
+			/* Wot, we can't get the same setup we had before? */
+			dev_err(&host->spi->dev,
+					"can't restore chip-select polarity\n");
+		}
+	}
+}
+
+static char *mmc_powerstring(u8 power_mode)
+{
+	switch (power_mode) {
+	case MMC_POWER_OFF: return "off";
+	case MMC_POWER_UP:  return "up";
+	case MMC_POWER_ON:  return "on";
+	}
+	return "?";
+}
+
+static void mmc_spi_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
+{
+	struct mmc_spi_host *host = mmc_priv(mmc);
+
+	if (host->power_mode != ios->power_mode) {
+		int		canpower;
+
+		canpower = host->pdata && host->pdata->setpower;
+
+		dev_dbg(&host->spi->dev, "power %s (%d)%s\n",
+				mmc_powerstring(ios->power_mode),
+				ios->vdd,
+				canpower ? ", can switch" : "");
+
+		/* switch power on/off if possible, accounting for
+		 * max 250msec powerup time if needed.
+		 */
+		if (canpower) {
+			switch (ios->power_mode) {
+			case MMC_POWER_OFF:
+			case MMC_POWER_UP:
+				host->pdata->setpower(&host->spi->dev,
+						ios->vdd);
+				if (ios->power_mode == MMC_POWER_UP)
+					msleep(host->powerup_msecs);
+			}
+		}
+
+		/* See 6.4.1 in the simplified SD card physical spec 2.0 */
+		if (ios->power_mode == MMC_POWER_ON)
+			mmc_spi_initsequence(host);
+
+		/* If powering down, ground all card inputs to avoid power
+		 * delivery from data lines!  On a shared SPI bus, this
+		 * will probably be temporary; 6.4.2 of the simplified SD
+		 * spec says this must last at least 1msec.
+		 *
+		 *   - Clock low means CPOL 0, e.g. mode 0
+		 *   - MOSI low comes from writing zero
+		 *   - Chipselect is usually active low...
+		 */
+		if (canpower && ios->power_mode == MMC_POWER_OFF) {
+			int mres;
+			u8 nullbyte = 0;
+
+			host->spi->mode &= ~(SPI_CPOL|SPI_CPHA);
+			mres = spi_setup(host->spi);
+			if (mres < 0)
+				dev_dbg(&host->spi->dev,
+					"switch to SPI mode 0 failed\n");
+
+			if (spi_write(host->spi, &nullbyte, 1) < 0)
+				dev_dbg(&host->spi->dev,
+					"put spi signals to low failed\n");
+
+			/*
+			 * Now clock should be low due to spi mode 0;
+			 * MOSI should be low because of written 0x00;
+			 * chipselect should be low (it is active low)
+			 * power supply is off, so now MMC is off too!
+			 *
+			 * FIXME no, chipselect can be high since the
+			 * device is inactive and SPI_CS_HIGH is clear...
+			 */
+			msleep(10);
+			if (mres == 0) {
+				host->spi->mode |= (SPI_CPOL|SPI_CPHA);
+				mres = spi_setup(host->spi);
+				if (mres < 0)
+					dev_dbg(&host->spi->dev,
+						"switch back to SPI mode 3 failed\n");
+			}
+		}
+
+		host->power_mode = ios->power_mode;
+	}
+
+	if (host->spi->max_speed_hz != ios->clock && ios->clock != 0) {
+		int		status;
+
+		host->spi->max_speed_hz = ios->clock;
+		status = spi_setup(host->spi);
+		dev_dbg(&host->spi->dev, "  clock to %d Hz, %d\n",
+			host->spi->max_speed_hz, status);
+	}
+}
+
+static const struct mmc_host_ops mmc_spi_ops = {
+	.request	= mmc_spi_request,
+	.set_ios	= mmc_spi_set_ios,
+	.get_ro		= mmc_gpio_get_ro,
+	.get_cd		= mmc_gpio_get_cd,
+};
+
+
+/****************************************************************************/
+
+/*
+ * SPI driver implementation
+ */
+
+static irqreturn_t
+mmc_spi_detect_irq(int irq, void *mmc)
+{
+	struct mmc_spi_host *host = mmc_priv(mmc);
+	u16 delay_msec = max(host->pdata->detect_delay, (u16)100);
+
+	mmc_detect_change(mmc, msecs_to_jiffies(delay_msec));
+	return IRQ_HANDLED;
+}
+
+static int mmc_spi_probe(struct spi_device *spi)
+{
+	void			*ones;
+	struct mmc_host		*mmc;
+	struct mmc_spi_host	*host;
+	int			status;
+	bool			has_ro = false;
+
+	/* We rely on full duplex transfers, mostly to reduce
+	 * per-transfer overheads (by making fewer transfers).
+	 */
+	if (spi->master->flags & SPI_MASTER_HALF_DUPLEX)
+		return -EINVAL;
+
+	/* MMC and SD specs only seem to care that sampling is on the
+	 * rising edge ... meaning SPI modes 0 or 3.  So either SPI mode
+	 * should be legit.  We'll use mode 0 since the steady state is 0,
+	 * which is appropriate for hotplugging, unless the platform data
+	 * specify mode 3 (if hardware is not compatible to mode 0).
+	 */
+	if (spi->mode != SPI_MODE_3)
+		spi->mode = SPI_MODE_0;
+	spi->bits_per_word = 8;
+
+	status = spi_setup(spi);
+	if (status < 0) {
+		dev_dbg(&spi->dev, "needs SPI mode %02x, %d KHz; %d\n",
+				spi->mode, spi->max_speed_hz / 1000,
+				status);
+		return status;
+	}
+
+	/* We need a supply of ones to transmit.  This is the only time
+	 * the CPU touches these, so cache coherency isn't a concern.
+	 *
+	 * NOTE if many systems use more than one MMC-over-SPI connector
+	 * it'd save some memory to share this.  That's evidently rare.
+	 */
+	status = -ENOMEM;
+	ones = kmalloc(MMC_SPI_BLOCKSIZE, GFP_KERNEL);
+	if (!ones)
+		goto nomem;
+	memset(ones, 0xff, MMC_SPI_BLOCKSIZE);
+
+	mmc = mmc_alloc_host(sizeof(*host), &spi->dev);
+	if (!mmc)
+		goto nomem;
+
+	mmc->ops = &mmc_spi_ops;
+	mmc->max_blk_size = MMC_SPI_BLOCKSIZE;
+	mmc->max_segs = MMC_SPI_BLOCKSATONCE;
+	mmc->max_req_size = MMC_SPI_BLOCKSATONCE * MMC_SPI_BLOCKSIZE;
+	mmc->max_blk_count = MMC_SPI_BLOCKSATONCE;
+
+	mmc->caps = MMC_CAP_SPI;
+
+	/* SPI doesn't need the lowspeed device identification thing for
+	 * MMC or SD cards, since it never comes up in open drain mode.
+	 * That's good; some SPI masters can't handle very low speeds!
+	 *
+	 * However, low speed SDIO cards need not handle over 400 KHz;
+	 * that's the only reason not to use a few MHz for f_min (until
+	 * the upper layer reads the target frequency from the CSD).
+	 */
+	mmc->f_min = 400000;
+	mmc->f_max = spi->max_speed_hz;
+
+	host = mmc_priv(mmc);
+	host->mmc = mmc;
+	host->spi = spi;
+
+	host->ones = ones;
+
+	dev_set_drvdata(&spi->dev, mmc);
+
+	/* Platform data is used to hook up things like card sensing
+	 * and power switching gpios.
+	 */
+	host->pdata = mmc_spi_get_pdata(spi);
+	if (host->pdata)
+		mmc->ocr_avail = host->pdata->ocr_mask;
+	if (!mmc->ocr_avail) {
+		dev_warn(&spi->dev, "ASSUMING 3.2-3.4 V slot power\n");
+		mmc->ocr_avail = MMC_VDD_32_33|MMC_VDD_33_34;
+	}
+	if (host->pdata && host->pdata->setpower) {
+		host->powerup_msecs = host->pdata->powerup_msecs;
+		if (!host->powerup_msecs || host->powerup_msecs > 250)
+			host->powerup_msecs = 250;
+	}
+
+	/* Preallocate buffers */
+	host->data = kmalloc(sizeof(*host->data), GFP_KERNEL);
+	if (!host->data)
+		goto fail_nobuf1;
+
+	/* setup message for status/busy readback */
+	spi_message_init(&host->readback);
+
+	spi_message_add_tail(&host->status, &host->readback);
+	host->status.tx_buf = host->ones;
+	host->status.rx_buf = &host->data->status;
+	host->status.cs_change = 1;
+
+	/* register card detect irq */
+	if (host->pdata && host->pdata->init) {
+		status = host->pdata->init(&spi->dev, mmc_spi_detect_irq, mmc);
+		if (status != 0)
+			goto fail_glue_init;
+	}
+
+	/* pass platform capabilities, if any */
+	if (host->pdata) {
+		mmc->caps |= host->pdata->caps;
+		mmc->caps2 |= host->pdata->caps2;
+	}
+
+	status = mmc_add_host(mmc);
+	if (status != 0)
+		goto fail_glue_init;
+
+	/*
+	 * Index 0 is card detect
+	 * Old boardfiles were specifying 1 ms as debounce
+	 */
+	status = mmc_gpiod_request_cd(mmc, NULL, 0, false, 1000);
+	if (status == -EPROBE_DEFER)
+		goto fail_gpiod_request;
+	if (!status) {
+		/*
+		 * The platform has a CD GPIO signal that may support
+		 * interrupts, so let mmc_gpiod_request_cd_irq() decide
+		 * if polling is needed or not.
+		 */
+		mmc->caps &= ~MMC_CAP_NEEDS_POLL;
+		mmc_gpiod_request_cd_irq(mmc);
+	}
+	mmc_detect_change(mmc, 0);
+
+	/* Index 1 is write protect/read only */
+	status = mmc_gpiod_request_ro(mmc, NULL, 1, 0);
+	if (status == -EPROBE_DEFER)
+		goto fail_gpiod_request;
+	if (!status)
+		has_ro = true;
+
+	dev_info(&spi->dev, "SD/MMC host %s%s%s%s\n",
+			dev_name(&mmc->class_dev),
+			has_ro ? "" : ", no WP",
+			(host->pdata && host->pdata->setpower)
+				? "" : ", no poweroff",
+			(mmc->caps & MMC_CAP_NEEDS_POLL)
+				? ", cd polling" : "");
+	return 0;
+
+fail_gpiod_request:
+	mmc_remove_host(mmc);
+fail_glue_init:
+	kfree(host->data);
+fail_nobuf1:
+	mmc_spi_put_pdata(spi);
+	mmc_free_host(mmc);
+nomem:
+	kfree(ones);
+	return status;
+}
+
+
+static void mmc_spi_remove(struct spi_device *spi)
+{
+	struct mmc_host		*mmc = dev_get_drvdata(&spi->dev);
+	struct mmc_spi_host	*host = mmc_priv(mmc);
+
+	/* prevent new mmc_detect_change() calls */
+	if (host->pdata && host->pdata->exit)
+		host->pdata->exit(&spi->dev, mmc);
+
+	mmc_remove_host(mmc);
+
+	kfree(host->data);
+	kfree(host->ones);
+
+	spi->max_speed_hz = mmc->f_max;
+	mmc_spi_put_pdata(spi);
+	mmc_free_host(mmc);
+}
+
+static const struct spi_device_id mmc_spi_dev_ids[] = {
+	{ "mmc-spi-slot"},
+	{ },
+};
+MODULE_DEVICE_TABLE(spi, mmc_spi_dev_ids);
+
+static const struct of_device_id mmc_spi_of_match_table[] = {
+	{ .compatible = "mmc-spi-slot", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mmc_spi_of_match_table);
+
+static struct spi_driver mmc_spi_driver = {
+	.driver = {
+		.name =		"mmc_spi",
+		.of_match_table = mmc_spi_of_match_table,
+	},
+	.id_table =	mmc_spi_dev_ids,
+	.probe =	mmc_spi_probe,
+	.remove =	mmc_spi_remove,
+};
+
+module_spi_driver(mmc_spi_driver);
+
+MODULE_AUTHOR("Mike Lavender, David Brownell, Hans-Peter Nilsson, Jan Nikitenko");
+MODULE_DESCRIPTION("SPI SD/MMC host driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:mmc_spi");