1 files changed, 453 insertions, 0 deletions
diff --git a/drivers/spi/spi-bitbang.c b/drivers/spi/spi-bitbang.c
new file mode 100644
index 000000000..27d0087f8
--- /dev/null
+++ b/drivers/spi/spi-bitbang.c
@@ -0,0 +1,453 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * polling/bitbanging SPI master controller driver utilities
+ */
+
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <linux/spi/spi.h>
+#include <linux/spi/spi_bitbang.h>
+
+#define SPI_BITBANG_CS_DELAY	100
+
+
+/*----------------------------------------------------------------------*/
+
+/*
+ * FIRST PART (OPTIONAL):  word-at-a-time spi_transfer support.
+ * Use this for GPIO or shift-register level hardware APIs.
+ *
+ * spi_bitbang_cs is in spi_device->controller_state, which is unavailable
+ * to glue code.  These bitbang setup() and cleanup() routines are always
+ * used, though maybe they're called from controller-aware code.
+ *
+ * chipselect() and friends may use spi_device->controller_data and
+ * controller registers as appropriate.
+ *
+ *
+ * NOTE:  SPI controller pins can often be used as GPIO pins instead,
+ * which means you could use a bitbang driver either to get hardware
+ * working quickly, or testing for differences that aren't speed related.
+ */
+
+struct spi_bitbang_cs {
+	unsigned	nsecs;	/* (clock cycle time)/2 */
+	u32		(*txrx_word)(struct spi_device *spi, unsigned nsecs,
+					u32 word, u8 bits, unsigned flags);
+	unsigned	(*txrx_bufs)(struct spi_device *,
+					u32 (*txrx_word)(
+						struct spi_device *spi,
+						unsigned nsecs,
+						u32 word, u8 bits,
+						unsigned flags),
+					unsigned, struct spi_transfer *,
+					unsigned);
+};
+
+static unsigned bitbang_txrx_8(
+	struct spi_device	*spi,
+	u32			(*txrx_word)(struct spi_device *spi,
+					unsigned nsecs,
+					u32 word, u8 bits,
+					unsigned flags),
+	unsigned		ns,
+	struct spi_transfer	*t,
+	unsigned flags
+)
+{
+	unsigned		bits = t->bits_per_word;
+	unsigned		count = t->len;
+	const u8		*tx = t->tx_buf;
+	u8			*rx = t->rx_buf;
+
+	while (likely(count > 0)) {
+		u8		word = 0;
+
+		if (tx)
+			word = *tx++;
+		word = txrx_word(spi, ns, word, bits, flags);
+		if (rx)
+			*rx++ = word;
+		count -= 1;
+	}
+	return t->len - count;
+}
+
+static unsigned bitbang_txrx_16(
+	struct spi_device	*spi,
+	u32			(*txrx_word)(struct spi_device *spi,
+					unsigned nsecs,
+					u32 word, u8 bits,
+					unsigned flags),
+	unsigned		ns,
+	struct spi_transfer	*t,
+	unsigned flags
+)
+{
+	unsigned		bits = t->bits_per_word;
+	unsigned		count = t->len;
+	const u16		*tx = t->tx_buf;
+	u16			*rx = t->rx_buf;
+
+	while (likely(count > 1)) {
+		u16		word = 0;
+
+		if (tx)
+			word = *tx++;
+		word = txrx_word(spi, ns, word, bits, flags);
+		if (rx)
+			*rx++ = word;
+		count -= 2;
+	}
+	return t->len - count;
+}
+
+static unsigned bitbang_txrx_32(
+	struct spi_device	*spi,
+	u32			(*txrx_word)(struct spi_device *spi,
+					unsigned nsecs,
+					u32 word, u8 bits,
+					unsigned flags),
+	unsigned		ns,
+	struct spi_transfer	*t,
+	unsigned flags
+)
+{
+	unsigned		bits = t->bits_per_word;
+	unsigned		count = t->len;
+	const u32		*tx = t->tx_buf;
+	u32			*rx = t->rx_buf;
+
+	while (likely(count > 3)) {
+		u32		word = 0;
+
+		if (tx)
+			word = *tx++;
+		word = txrx_word(spi, ns, word, bits, flags);
+		if (rx)
+			*rx++ = word;
+		count -= 4;
+	}
+	return t->len - count;
+}
+
+int spi_bitbang_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
+{
+	struct spi_bitbang_cs	*cs = spi->controller_state;
+	u8			bits_per_word;
+	u32			hz;
+
+	if (t) {
+		bits_per_word = t->bits_per_word;
+		hz = t->speed_hz;
+	} else {
+		bits_per_word = 0;
+		hz = 0;
+	}
+
+	/* spi_transfer level calls that work per-word */
+	if (!bits_per_word)
+		bits_per_word = spi->bits_per_word;
+	if (bits_per_word <= 8)
+		cs->txrx_bufs = bitbang_txrx_8;
+	else if (bits_per_word <= 16)
+		cs->txrx_bufs = bitbang_txrx_16;
+	else if (bits_per_word <= 32)
+		cs->txrx_bufs = bitbang_txrx_32;
+	else
+		return -EINVAL;
+
+	/* nsecs = (clock period)/2 */
+	if (!hz)
+		hz = spi->max_speed_hz;
+	if (hz) {
+		cs->nsecs = (1000000000/2) / hz;
+		if (cs->nsecs > (MAX_UDELAY_MS * 1000 * 1000))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_setup_transfer);
+
+/*
+ * spi_bitbang_setup - default setup for per-word I/O loops
+ */
+int spi_bitbang_setup(struct spi_device *spi)
+{
+	struct spi_bitbang_cs	*cs = spi->controller_state;
+	struct spi_bitbang	*bitbang;
+	bool			initial_setup = false;
+	int			retval;
+
+	bitbang = spi_master_get_devdata(spi->master);
+
+	if (!cs) {
+		cs = kzalloc(sizeof(*cs), GFP_KERNEL);
+		if (!cs)
+			return -ENOMEM;
+		spi->controller_state = cs;
+		initial_setup = true;
+	}
+
+	/* per-word shift register access, in hardware or bitbanging */
+	cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
+	if (!cs->txrx_word) {
+		retval = -EINVAL;
+		goto err_free;
+	}
+
+	if (bitbang->setup_transfer) {
+		retval = bitbang->setup_transfer(spi, NULL);
+		if (retval < 0)
+			goto err_free;
+	}
+
+	dev_dbg(&spi->dev, "%s, %u nsec/bit\n", __func__, 2 * cs->nsecs);
+
+	return 0;
+
+err_free:
+	if (initial_setup)
+		kfree(cs);
+	return retval;
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_setup);
+
+/*
+ * spi_bitbang_cleanup - default cleanup for per-word I/O loops
+ */
+void spi_bitbang_cleanup(struct spi_device *spi)
+{
+	kfree(spi->controller_state);
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_cleanup);
+
+static int spi_bitbang_bufs(struct spi_device *spi, struct spi_transfer *t)
+{
+	struct spi_bitbang_cs	*cs = spi->controller_state;
+	unsigned		nsecs = cs->nsecs;
+	struct spi_bitbang	*bitbang;
+
+	bitbang = spi_master_get_devdata(spi->master);
+	if (bitbang->set_line_direction) {
+		int err;
+
+		err = bitbang->set_line_direction(spi, !!(t->tx_buf));
+		if (err < 0)
+			return err;
+	}
+
+	if (spi->mode & SPI_3WIRE) {
+		unsigned flags;
+
+		flags = t->tx_buf ? SPI_MASTER_NO_RX : SPI_MASTER_NO_TX;
+		return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, flags);
+	}
+	return cs->txrx_bufs(spi, cs->txrx_word, nsecs, t, 0);
+}
+
+/*----------------------------------------------------------------------*/
+
+/*
+ * SECOND PART ... simple transfer queue runner.
+ *
+ * This costs a task context per controller, running the queue by
+ * performing each transfer in sequence.  Smarter hardware can queue
+ * several DMA transfers at once, and process several controller queues
+ * in parallel; this driver doesn't match such hardware very well.
+ *
+ * Drivers can provide word-at-a-time i/o primitives, or provide
+ * transfer-at-a-time ones to leverage dma or fifo hardware.
+ */
+
+static int spi_bitbang_prepare_hardware(struct spi_master *spi)
+{
+	struct spi_bitbang	*bitbang;
+
+	bitbang = spi_master_get_devdata(spi);
+
+	mutex_lock(&bitbang->lock);
+	bitbang->busy = 1;
+	mutex_unlock(&bitbang->lock);
+
+	return 0;
+}
+
+static int spi_bitbang_transfer_one(struct spi_master *master,
+				    struct spi_device *spi,
+				    struct spi_transfer *transfer)
+{
+	struct spi_bitbang *bitbang = spi_master_get_devdata(master);
+	int status = 0;
+
+	if (bitbang->setup_transfer) {
+		status = bitbang->setup_transfer(spi, transfer);
+		if (status < 0)
+			goto out;
+	}
+
+	if (transfer->len)
+		status = bitbang->txrx_bufs(spi, transfer);
+
+	if (status == transfer->len)
+		status = 0;
+	else if (status >= 0)
+		status = -EREMOTEIO;
+
+out:
+	spi_finalize_current_transfer(master);
+
+	return status;
+}
+
+static int spi_bitbang_unprepare_hardware(struct spi_master *spi)
+{
+	struct spi_bitbang	*bitbang;
+
+	bitbang = spi_master_get_devdata(spi);
+
+	mutex_lock(&bitbang->lock);
+	bitbang->busy = 0;
+	mutex_unlock(&bitbang->lock);
+
+	return 0;
+}
+
+static void spi_bitbang_set_cs(struct spi_device *spi, bool enable)
+{
+	struct spi_bitbang *bitbang = spi_master_get_devdata(spi->master);
+
+	/* SPI core provides CS high / low, but bitbang driver
+	 * expects CS active
+	 * spi device driver takes care of handling SPI_CS_HIGH
+	 */
+	enable = (!!(spi->mode & SPI_CS_HIGH) == enable);
+
+	ndelay(SPI_BITBANG_CS_DELAY);
+	bitbang->chipselect(spi, enable ? BITBANG_CS_ACTIVE :
+			    BITBANG_CS_INACTIVE);
+	ndelay(SPI_BITBANG_CS_DELAY);
+}
+
+/*----------------------------------------------------------------------*/
+
+int spi_bitbang_init(struct spi_bitbang *bitbang)
+{
+	struct spi_master *master = bitbang->master;
+	bool custom_cs;
+
+	if (!master)
+		return -EINVAL;
+	/*
+	 * We only need the chipselect callback if we are actually using it.
+	 * If we just use GPIO descriptors, it is surplus. If the
+	 * SPI_MASTER_GPIO_SS flag is set, we always need to call the
+	 * driver-specific chipselect routine.
+	 */
+	custom_cs = (!master->use_gpio_descriptors ||
+		     (master->flags & SPI_MASTER_GPIO_SS));
+
+	if (custom_cs && !bitbang->chipselect)
+		return -EINVAL;
+
+	mutex_init(&bitbang->lock);
+
+	if (!master->mode_bits)
+		master->mode_bits = SPI_CPOL | SPI_CPHA | bitbang->flags;
+
+	if (master->transfer || master->transfer_one_message)
+		return -EINVAL;
+
+	master->prepare_transfer_hardware = spi_bitbang_prepare_hardware;
+	master->unprepare_transfer_hardware = spi_bitbang_unprepare_hardware;
+	master->transfer_one = spi_bitbang_transfer_one;
+	/*
+	 * When using GPIO descriptors, the ->set_cs() callback doesn't even
+	 * get called unless SPI_MASTER_GPIO_SS is set.
+	 */
+	if (custom_cs)
+		master->set_cs = spi_bitbang_set_cs;
+
+	if (!bitbang->txrx_bufs) {
+		bitbang->use_dma = 0;
+		bitbang->txrx_bufs = spi_bitbang_bufs;
+		if (!master->setup) {
+			if (!bitbang->setup_transfer)
+				bitbang->setup_transfer =
+					 spi_bitbang_setup_transfer;
+			master->setup = spi_bitbang_setup;
+			master->cleanup = spi_bitbang_cleanup;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_init);
+
+/**
+ * spi_bitbang_start - start up a polled/bitbanging SPI master driver
+ * @bitbang: driver handle
+ *
+ * Caller should have zero-initialized all parts of the structure, and then
+ * provided callbacks for chip selection and I/O loops.  If the master has
+ * a transfer method, its final step should call spi_bitbang_transfer; or,
+ * that's the default if the transfer routine is not initialized.  It should
+ * also set up the bus number and number of chipselects.
+ *
+ * For i/o loops, provide callbacks either per-word (for bitbanging, or for
+ * hardware that basically exposes a shift register) or per-spi_transfer
+ * (which takes better advantage of hardware like fifos or DMA engines).
+ *
+ * Drivers using per-word I/O loops should use (or call) spi_bitbang_setup,
+ * spi_bitbang_cleanup and spi_bitbang_setup_transfer to handle those spi
+ * master methods.  Those methods are the defaults if the bitbang->txrx_bufs
+ * routine isn't initialized.
+ *
+ * This routine registers the spi_master, which will process requests in a
+ * dedicated task, keeping IRQs unblocked most of the time.  To stop
+ * processing those requests, call spi_bitbang_stop().
+ *
+ * On success, this routine will take a reference to master. The caller is
+ * responsible for calling spi_bitbang_stop() to decrement the reference and
+ * spi_master_put() as counterpart of spi_alloc_master() to prevent a memory
+ * leak.
+ */
+int spi_bitbang_start(struct spi_bitbang *bitbang)
+{
+	struct spi_master *master = bitbang->master;
+	int ret;
+
+	ret = spi_bitbang_init(bitbang);
+	if (ret)
+		return ret;
+
+	/* driver may get busy before register() returns, especially
+	 * if someone registered boardinfo for devices
+	 */
+	ret = spi_register_master(spi_master_get(master));
+	if (ret)
+		spi_master_put(master);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_start);
+
+/*
+ * spi_bitbang_stop - stops the task providing spi communication
+ */
+void spi_bitbang_stop(struct spi_bitbang *bitbang)
+{
+	spi_unregister_master(bitbang->master);
+}
+EXPORT_SYMBOL_GPL(spi_bitbang_stop);
+
+MODULE_LICENSE("GPL");
+