Adding upstream version 5.10.209.upstream/5.10.209upstream

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

1 files changed, 992 insertions, 0 deletions

diff --git a/drivers/spi/spi-au1550.c b/drivers/spi/spi-au1550.c
new file mode 100644
index 000000000..dfb7196f4
--- /dev/null
+++ b/drivers/spi/spi-au1550.c
@@ -0,0 +1,992 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * au1550 psc spi controller driver
+ * may work also with au1200, au1210, au1250
+ * will not work on au1000, au1100 and au1500 (no full spi controller there)
+ *
+ * Copyright (c) 2006 ATRON electronic GmbH
+ * Author: Jan Nikitenko <jan.nikitenko@gmail.com>
+ */
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/resource.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/spi_bitbang.h>
+#include <linux/dma-mapping.h>
+#include <linux/completion.h>
+#include <asm/mach-au1x00/au1000.h>
+#include <asm/mach-au1x00/au1xxx_psc.h>
+#include <asm/mach-au1x00/au1xxx_dbdma.h>
+
+#include <asm/mach-au1x00/au1550_spi.h>
+
+static unsigned usedma = 1;
+module_param(usedma, uint, 0644);
+
+/*
+#define AU1550_SPI_DEBUG_LOOPBACK
+*/
+
+
+#define AU1550_SPI_DBDMA_DESCRIPTORS 1
+#define AU1550_SPI_DMA_RXTMP_MINSIZE 2048U
+
+struct au1550_spi {
+	struct spi_bitbang bitbang;
+
+	volatile psc_spi_t __iomem *regs;
+	int irq;
+
+	unsigned len;
+	unsigned tx_count;
+	unsigned rx_count;
+	const u8 *tx;
+	u8 *rx;
+
+	void (*rx_word)(struct au1550_spi *hw);
+	void (*tx_word)(struct au1550_spi *hw);
+	int (*txrx_bufs)(struct spi_device *spi, struct spi_transfer *t);
+	irqreturn_t (*irq_callback)(struct au1550_spi *hw);
+
+	struct completion master_done;
+
+	unsigned usedma;
+	u32 dma_tx_id;
+	u32 dma_rx_id;
+	u32 dma_tx_ch;
+	u32 dma_rx_ch;
+
+	u8 *dma_rx_tmpbuf;
+	unsigned dma_rx_tmpbuf_size;
+	u32 dma_rx_tmpbuf_addr;
+
+	struct spi_master *master;
+	struct device *dev;
+	struct au1550_spi_info *pdata;
+	struct resource *ioarea;
+};
+
+
+/* we use an 8-bit memory device for dma transfers to/from spi fifo */
+static dbdev_tab_t au1550_spi_mem_dbdev =
+{
+	.dev_id			= DBDMA_MEM_CHAN,
+	.dev_flags		= DEV_FLAGS_ANYUSE|DEV_FLAGS_SYNC,
+	.dev_tsize		= 0,
+	.dev_devwidth		= 8,
+	.dev_physaddr		= 0x00000000,
+	.dev_intlevel		= 0,
+	.dev_intpolarity	= 0
+};
+
+static int ddma_memid;	/* id to above mem dma device */
+
+static void au1550_spi_bits_handlers_set(struct au1550_spi *hw, int bpw);
+
+
+/*
+ *  compute BRG and DIV bits to setup spi clock based on main input clock rate
+ *  that was specified in platform data structure
+ *  according to au1550 datasheet:
+ *    psc_tempclk = psc_mainclk / (2 << DIV)
+ *    spiclk = psc_tempclk / (2 * (BRG + 1))
+ *    BRG valid range is 4..63
+ *    DIV valid range is 0..3
+ */
+static u32 au1550_spi_baudcfg(struct au1550_spi *hw, unsigned speed_hz)
+{
+	u32 mainclk_hz = hw->pdata->mainclk_hz;
+	u32 div, brg;
+
+	for (div = 0; div < 4; div++) {
+		brg = mainclk_hz / speed_hz / (4 << div);
+		/* now we have BRG+1 in brg, so count with that */
+		if (brg < (4 + 1)) {
+			brg = (4 + 1);	/* speed_hz too big */
+			break;		/* set lowest brg (div is == 0) */
+		}
+		if (brg <= (63 + 1))
+			break;		/* we have valid brg and div */
+	}
+	if (div == 4) {
+		div = 3;		/* speed_hz too small */
+		brg = (63 + 1);		/* set highest brg and div */
+	}
+	brg--;
+	return PSC_SPICFG_SET_BAUD(brg) | PSC_SPICFG_SET_DIV(div);
+}
+
+static inline void au1550_spi_mask_ack_all(struct au1550_spi *hw)
+{
+	hw->regs->psc_spimsk =
+		  PSC_SPIMSK_MM | PSC_SPIMSK_RR | PSC_SPIMSK_RO
+		| PSC_SPIMSK_RU | PSC_SPIMSK_TR | PSC_SPIMSK_TO
+		| PSC_SPIMSK_TU | PSC_SPIMSK_SD | PSC_SPIMSK_MD;
+	wmb(); /* drain writebuffer */
+
+	hw->regs->psc_spievent =
+		  PSC_SPIEVNT_MM | PSC_SPIEVNT_RR | PSC_SPIEVNT_RO
+		| PSC_SPIEVNT_RU | PSC_SPIEVNT_TR | PSC_SPIEVNT_TO
+		| PSC_SPIEVNT_TU | PSC_SPIEVNT_SD | PSC_SPIEVNT_MD;
+	wmb(); /* drain writebuffer */
+}
+
+static void au1550_spi_reset_fifos(struct au1550_spi *hw)
+{
+	u32 pcr;
+
+	hw->regs->psc_spipcr = PSC_SPIPCR_RC | PSC_SPIPCR_TC;
+	wmb(); /* drain writebuffer */
+	do {
+		pcr = hw->regs->psc_spipcr;
+		wmb(); /* drain writebuffer */
+	} while (pcr != 0);
+}
+
+/*
+ * dma transfers are used for the most common spi word size of 8-bits
+ * we cannot easily change already set up dma channels' width, so if we wanted
+ * dma support for more than 8-bit words (up to 24 bits), we would need to
+ * setup dma channels from scratch on each spi transfer, based on bits_per_word
+ * instead we have pre set up 8 bit dma channels supporting spi 4 to 8 bits
+ * transfers, and 9 to 24 bits spi transfers will be done in pio irq based mode
+ * callbacks to handle dma or pio are set up in au1550_spi_bits_handlers_set()
+ */
+static void au1550_spi_chipsel(struct spi_device *spi, int value)
+{
+	struct au1550_spi *hw = spi_master_get_devdata(spi->master);
+	unsigned cspol = spi->mode & SPI_CS_HIGH ? 1 : 0;
+	u32 cfg, stat;
+
+	switch (value) {
+	case BITBANG_CS_INACTIVE:
+		if (hw->pdata->deactivate_cs)
+			hw->pdata->deactivate_cs(hw->pdata, spi->chip_select,
+					cspol);
+		break;
+
+	case BITBANG_CS_ACTIVE:
+		au1550_spi_bits_handlers_set(hw, spi->bits_per_word);
+
+		cfg = hw->regs->psc_spicfg;
+		wmb(); /* drain writebuffer */
+		hw->regs->psc_spicfg = cfg & ~PSC_SPICFG_DE_ENABLE;
+		wmb(); /* drain writebuffer */
+
+		if (spi->mode & SPI_CPOL)
+			cfg |= PSC_SPICFG_BI;
+		else
+			cfg &= ~PSC_SPICFG_BI;
+		if (spi->mode & SPI_CPHA)
+			cfg &= ~PSC_SPICFG_CDE;
+		else
+			cfg |= PSC_SPICFG_CDE;
+
+		if (spi->mode & SPI_LSB_FIRST)
+			cfg |= PSC_SPICFG_MLF;
+		else
+			cfg &= ~PSC_SPICFG_MLF;
+
+		if (hw->usedma && spi->bits_per_word <= 8)
+			cfg &= ~PSC_SPICFG_DD_DISABLE;
+		else
+			cfg |= PSC_SPICFG_DD_DISABLE;
+		cfg = PSC_SPICFG_CLR_LEN(cfg);
+		cfg |= PSC_SPICFG_SET_LEN(spi->bits_per_word);
+
+		cfg = PSC_SPICFG_CLR_BAUD(cfg);
+		cfg &= ~PSC_SPICFG_SET_DIV(3);
+		cfg |= au1550_spi_baudcfg(hw, spi->max_speed_hz);
+
+		hw->regs->psc_spicfg = cfg | PSC_SPICFG_DE_ENABLE;
+		wmb(); /* drain writebuffer */
+		do {
+			stat = hw->regs->psc_spistat;
+			wmb(); /* drain writebuffer */
+		} while ((stat & PSC_SPISTAT_DR) == 0);
+
+		if (hw->pdata->activate_cs)
+			hw->pdata->activate_cs(hw->pdata, spi->chip_select,
+					cspol);
+		break;
+	}
+}
+
+static int au1550_spi_setupxfer(struct spi_device *spi, struct spi_transfer *t)
+{
+	struct au1550_spi *hw = spi_master_get_devdata(spi->master);
+	unsigned bpw, hz;
+	u32 cfg, stat;
+
+	if (t) {
+		bpw = t->bits_per_word;
+		hz = t->speed_hz;
+	} else {
+		bpw = spi->bits_per_word;
+		hz = spi->max_speed_hz;
+	}
+
+	if (!hz)
+		return -EINVAL;
+
+	au1550_spi_bits_handlers_set(hw, spi->bits_per_word);
+
+	cfg = hw->regs->psc_spicfg;
+	wmb(); /* drain writebuffer */
+	hw->regs->psc_spicfg = cfg & ~PSC_SPICFG_DE_ENABLE;
+	wmb(); /* drain writebuffer */
+
+	if (hw->usedma && bpw <= 8)
+		cfg &= ~PSC_SPICFG_DD_DISABLE;
+	else
+		cfg |= PSC_SPICFG_DD_DISABLE;
+	cfg = PSC_SPICFG_CLR_LEN(cfg);
+	cfg |= PSC_SPICFG_SET_LEN(bpw);
+
+	cfg = PSC_SPICFG_CLR_BAUD(cfg);
+	cfg &= ~PSC_SPICFG_SET_DIV(3);
+	cfg |= au1550_spi_baudcfg(hw, hz);
+
+	hw->regs->psc_spicfg = cfg;
+	wmb(); /* drain writebuffer */
+
+	if (cfg & PSC_SPICFG_DE_ENABLE) {
+		do {
+			stat = hw->regs->psc_spistat;
+			wmb(); /* drain writebuffer */
+		} while ((stat & PSC_SPISTAT_DR) == 0);
+	}
+
+	au1550_spi_reset_fifos(hw);
+	au1550_spi_mask_ack_all(hw);
+	return 0;
+}
+
+/*
+ * for dma spi transfers, we have to setup rx channel, otherwise there is
+ * no reliable way how to recognize that spi transfer is done
+ * dma complete callbacks are called before real spi transfer is finished
+ * and if only tx dma channel is set up (and rx fifo overflow event masked)
+ * spi master done event irq is not generated unless rx fifo is empty (emptied)
+ * so we need rx tmp buffer to use for rx dma if user does not provide one
+ */
+static int au1550_spi_dma_rxtmp_alloc(struct au1550_spi *hw, unsigned size)
+{
+	hw->dma_rx_tmpbuf = kmalloc(size, GFP_KERNEL);
+	if (!hw->dma_rx_tmpbuf)
+		return -ENOMEM;
+	hw->dma_rx_tmpbuf_size = size;
+	hw->dma_rx_tmpbuf_addr = dma_map_single(hw->dev, hw->dma_rx_tmpbuf,
+			size, DMA_FROM_DEVICE);
+	if (dma_mapping_error(hw->dev, hw->dma_rx_tmpbuf_addr)) {
+		kfree(hw->dma_rx_tmpbuf);
+		hw->dma_rx_tmpbuf = 0;
+		hw->dma_rx_tmpbuf_size = 0;
+		return -EFAULT;
+	}
+	return 0;
+}
+
+static void au1550_spi_dma_rxtmp_free(struct au1550_spi *hw)
+{
+	dma_unmap_single(hw->dev, hw->dma_rx_tmpbuf_addr,
+			hw->dma_rx_tmpbuf_size, DMA_FROM_DEVICE);
+	kfree(hw->dma_rx_tmpbuf);
+	hw->dma_rx_tmpbuf = 0;
+	hw->dma_rx_tmpbuf_size = 0;
+}
+
+static int au1550_spi_dma_txrxb(struct spi_device *spi, struct spi_transfer *t)
+{
+	struct au1550_spi *hw = spi_master_get_devdata(spi->master);
+	dma_addr_t dma_tx_addr;
+	dma_addr_t dma_rx_addr;
+	u32 res;
+
+	hw->len = t->len;
+	hw->tx_count = 0;
+	hw->rx_count = 0;
+
+	hw->tx = t->tx_buf;
+	hw->rx = t->rx_buf;
+	dma_tx_addr = t->tx_dma;
+	dma_rx_addr = t->rx_dma;
+
+	/*
+	 * check if buffers are already dma mapped, map them otherwise:
+	 * - first map the TX buffer, so cache data gets written to memory
+	 * - then map the RX buffer, so that cache entries (with
+	 *   soon-to-be-stale data) get removed
+	 * use rx buffer in place of tx if tx buffer was not provided
+	 * use temp rx buffer (preallocated or realloc to fit) for rx dma
+	 */
+	if (t->tx_buf) {
+		if (t->tx_dma == 0) {	/* if DMA_ADDR_INVALID, map it */
+			dma_tx_addr = dma_map_single(hw->dev,
+					(void *)t->tx_buf,
+					t->len, DMA_TO_DEVICE);
+			if (dma_mapping_error(hw->dev, dma_tx_addr))
+				dev_err(hw->dev, "tx dma map error\n");
+		}
+	}
+
+	if (t->rx_buf) {
+		if (t->rx_dma == 0) {	/* if DMA_ADDR_INVALID, map it */
+			dma_rx_addr = dma_map_single(hw->dev,
+					(void *)t->rx_buf,
+					t->len, DMA_FROM_DEVICE);
+			if (dma_mapping_error(hw->dev, dma_rx_addr))
+				dev_err(hw->dev, "rx dma map error\n");
+		}
+	} else {
+		if (t->len > hw->dma_rx_tmpbuf_size) {
+			int ret;
+
+			au1550_spi_dma_rxtmp_free(hw);
+			ret = au1550_spi_dma_rxtmp_alloc(hw, max(t->len,
+					AU1550_SPI_DMA_RXTMP_MINSIZE));
+			if (ret < 0)
+				return ret;
+		}
+		hw->rx = hw->dma_rx_tmpbuf;
+		dma_rx_addr = hw->dma_rx_tmpbuf_addr;
+		dma_sync_single_for_device(hw->dev, dma_rx_addr,
+			t->len, DMA_FROM_DEVICE);
+	}
+
+	if (!t->tx_buf) {
+		dma_sync_single_for_device(hw->dev, dma_rx_addr,
+				t->len, DMA_BIDIRECTIONAL);
+		hw->tx = hw->rx;
+	}
+
+	/* put buffers on the ring */
+	res = au1xxx_dbdma_put_dest(hw->dma_rx_ch, virt_to_phys(hw->rx),
+				    t->len, DDMA_FLAGS_IE);
+	if (!res)
+		dev_err(hw->dev, "rx dma put dest error\n");
+
+	res = au1xxx_dbdma_put_source(hw->dma_tx_ch, virt_to_phys(hw->tx),
+				      t->len, DDMA_FLAGS_IE);
+	if (!res)
+		dev_err(hw->dev, "tx dma put source error\n");
+
+	au1xxx_dbdma_start(hw->dma_rx_ch);
+	au1xxx_dbdma_start(hw->dma_tx_ch);
+
+	/* by default enable nearly all events interrupt */
+	hw->regs->psc_spimsk = PSC_SPIMSK_SD;
+	wmb(); /* drain writebuffer */
+
+	/* start the transfer */
+	hw->regs->psc_spipcr = PSC_SPIPCR_MS;
+	wmb(); /* drain writebuffer */
+
+	wait_for_completion(&hw->master_done);
+
+	au1xxx_dbdma_stop(hw->dma_tx_ch);
+	au1xxx_dbdma_stop(hw->dma_rx_ch);
+
+	if (!t->rx_buf) {
+		/* using the temporal preallocated and premapped buffer */
+		dma_sync_single_for_cpu(hw->dev, dma_rx_addr, t->len,
+			DMA_FROM_DEVICE);
+	}
+	/* unmap buffers if mapped above */
+	if (t->rx_buf && t->rx_dma == 0 )
+		dma_unmap_single(hw->dev, dma_rx_addr, t->len,
+			DMA_FROM_DEVICE);
+	if (t->tx_buf && t->tx_dma == 0 )
+		dma_unmap_single(hw->dev, dma_tx_addr, t->len,
+			DMA_TO_DEVICE);
+
+	return hw->rx_count < hw->tx_count ? hw->rx_count : hw->tx_count;
+}
+
+static irqreturn_t au1550_spi_dma_irq_callback(struct au1550_spi *hw)
+{
+	u32 stat, evnt;
+
+	stat = hw->regs->psc_spistat;
+	evnt = hw->regs->psc_spievent;
+	wmb(); /* drain writebuffer */
+	if ((stat & PSC_SPISTAT_DI) == 0) {
+		dev_err(hw->dev, "Unexpected IRQ!\n");
+		return IRQ_NONE;
+	}
+
+	if ((evnt & (PSC_SPIEVNT_MM | PSC_SPIEVNT_RO
+				| PSC_SPIEVNT_RU | PSC_SPIEVNT_TO
+				| PSC_SPIEVNT_TU | PSC_SPIEVNT_SD))
+			!= 0) {
+		/*
+		 * due to an spi error we consider transfer as done,
+		 * so mask all events until before next transfer start
+		 * and stop the possibly running dma immediately
+		 */
+		au1550_spi_mask_ack_all(hw);
+		au1xxx_dbdma_stop(hw->dma_rx_ch);
+		au1xxx_dbdma_stop(hw->dma_tx_ch);
+
+		/* get number of transferred bytes */
+		hw->rx_count = hw->len - au1xxx_get_dma_residue(hw->dma_rx_ch);
+		hw->tx_count = hw->len - au1xxx_get_dma_residue(hw->dma_tx_ch);
+
+		au1xxx_dbdma_reset(hw->dma_rx_ch);
+		au1xxx_dbdma_reset(hw->dma_tx_ch);
+		au1550_spi_reset_fifos(hw);
+
+		if (evnt == PSC_SPIEVNT_RO)
+			dev_err(hw->dev,
+				"dma transfer: receive FIFO overflow!\n");
+		else
+			dev_err(hw->dev,
+				"dma transfer: unexpected SPI error "
+				"(event=0x%x stat=0x%x)!\n", evnt, stat);
+
+		complete(&hw->master_done);
+		return IRQ_HANDLED;
+	}
+
+	if ((evnt & PSC_SPIEVNT_MD) != 0) {
+		/* transfer completed successfully */
+		au1550_spi_mask_ack_all(hw);
+		hw->rx_count = hw->len;
+		hw->tx_count = hw->len;
+		complete(&hw->master_done);
+	}
+	return IRQ_HANDLED;
+}
+
+
+/* routines to handle different word sizes in pio mode */
+#define AU1550_SPI_RX_WORD(size, mask)					\
+static void au1550_spi_rx_word_##size(struct au1550_spi *hw)		\
+{									\
+	u32 fifoword = hw->regs->psc_spitxrx & (u32)(mask);		\
+	wmb(); /* drain writebuffer */					\
+	if (hw->rx) {							\
+		*(u##size *)hw->rx = (u##size)fifoword;			\
+		hw->rx += (size) / 8;					\
+	}								\
+	hw->rx_count += (size) / 8;					\
+}
+
+#define AU1550_SPI_TX_WORD(size, mask)					\
+static void au1550_spi_tx_word_##size(struct au1550_spi *hw)		\
+{									\
+	u32 fifoword = 0;						\
+	if (hw->tx) {							\
+		fifoword = *(u##size *)hw->tx & (u32)(mask);		\
+		hw->tx += (size) / 8;					\
+	}								\
+	hw->tx_count += (size) / 8;					\
+	if (hw->tx_count >= hw->len)					\
+		fifoword |= PSC_SPITXRX_LC;				\
+	hw->regs->psc_spitxrx = fifoword;				\
+	wmb(); /* drain writebuffer */					\
+}
+
+AU1550_SPI_RX_WORD(8,0xff)
+AU1550_SPI_RX_WORD(16,0xffff)
+AU1550_SPI_RX_WORD(32,0xffffff)
+AU1550_SPI_TX_WORD(8,0xff)
+AU1550_SPI_TX_WORD(16,0xffff)
+AU1550_SPI_TX_WORD(32,0xffffff)
+
+static int au1550_spi_pio_txrxb(struct spi_device *spi, struct spi_transfer *t)
+{
+	u32 stat, mask;
+	struct au1550_spi *hw = spi_master_get_devdata(spi->master);
+
+	hw->tx = t->tx_buf;
+	hw->rx = t->rx_buf;
+	hw->len = t->len;
+	hw->tx_count = 0;
+	hw->rx_count = 0;
+
+	/* by default enable nearly all events after filling tx fifo */
+	mask = PSC_SPIMSK_SD;
+
+	/* fill the transmit FIFO */
+	while (hw->tx_count < hw->len) {
+
+		hw->tx_word(hw);
+
+		if (hw->tx_count >= hw->len) {
+			/* mask tx fifo request interrupt as we are done */
+			mask |= PSC_SPIMSK_TR;
+		}
+
+		stat = hw->regs->psc_spistat;
+		wmb(); /* drain writebuffer */
+		if (stat & PSC_SPISTAT_TF)
+			break;
+	}
+
+	/* enable event interrupts */
+	hw->regs->psc_spimsk = mask;
+	wmb(); /* drain writebuffer */
+
+	/* start the transfer */
+	hw->regs->psc_spipcr = PSC_SPIPCR_MS;
+	wmb(); /* drain writebuffer */
+
+	wait_for_completion(&hw->master_done);
+
+	return hw->rx_count < hw->tx_count ? hw->rx_count : hw->tx_count;
+}
+
+static irqreturn_t au1550_spi_pio_irq_callback(struct au1550_spi *hw)
+{
+	int busy;
+	u32 stat, evnt;
+
+	stat = hw->regs->psc_spistat;
+	evnt = hw->regs->psc_spievent;
+	wmb(); /* drain writebuffer */
+	if ((stat & PSC_SPISTAT_DI) == 0) {
+		dev_err(hw->dev, "Unexpected IRQ!\n");
+		return IRQ_NONE;
+	}
+
+	if ((evnt & (PSC_SPIEVNT_MM | PSC_SPIEVNT_RO
+				| PSC_SPIEVNT_RU | PSC_SPIEVNT_TO
+				| PSC_SPIEVNT_SD))
+			!= 0) {
+		/*
+		 * due to an error we consider transfer as done,
+		 * so mask all events until before next transfer start
+		 */
+		au1550_spi_mask_ack_all(hw);
+		au1550_spi_reset_fifos(hw);
+		dev_err(hw->dev,
+			"pio transfer: unexpected SPI error "
+			"(event=0x%x stat=0x%x)!\n", evnt, stat);
+		complete(&hw->master_done);
+		return IRQ_HANDLED;
+	}
+
+	/*
+	 * while there is something to read from rx fifo
+	 * or there is a space to write to tx fifo:
+	 */
+	do {
+		busy = 0;
+		stat = hw->regs->psc_spistat;
+		wmb(); /* drain writebuffer */
+
+		/*
+		 * Take care to not let the Rx FIFO overflow.
+		 *
+		 * We only write a byte if we have read one at least. Initially,
+		 * the write fifo is full, so we should read from the read fifo
+		 * first.
+		 * In case we miss a word from the read fifo, we should get a
+		 * RO event and should back out.
+		 */
+		if (!(stat & PSC_SPISTAT_RE) && hw->rx_count < hw->len) {
+			hw->rx_word(hw);
+			busy = 1;
+
+			if (!(stat & PSC_SPISTAT_TF) && hw->tx_count < hw->len)
+				hw->tx_word(hw);
+		}
+	} while (busy);
+
+	hw->regs->psc_spievent = PSC_SPIEVNT_RR | PSC_SPIEVNT_TR;
+	wmb(); /* drain writebuffer */
+
+	/*
+	 * Restart the SPI transmission in case of a transmit underflow.
+	 * This seems to work despite the notes in the Au1550 data book
+	 * of Figure 8-4 with flowchart for SPI master operation:
+	 *
+	 * """Note 1: An XFR Error Interrupt occurs, unless masked,
+	 * for any of the following events: Tx FIFO Underflow,
+	 * Rx FIFO Overflow, or Multiple-master Error
+	 *    Note 2: In case of a Tx Underflow Error, all zeroes are
+	 * transmitted."""
+	 *
+	 * By simply restarting the spi transfer on Tx Underflow Error,
+	 * we assume that spi transfer was paused instead of zeroes
+	 * transmittion mentioned in the Note 2 of Au1550 data book.
+	 */
+	if (evnt & PSC_SPIEVNT_TU) {
+		hw->regs->psc_spievent = PSC_SPIEVNT_TU | PSC_SPIEVNT_MD;
+		wmb(); /* drain writebuffer */
+		hw->regs->psc_spipcr = PSC_SPIPCR_MS;
+		wmb(); /* drain writebuffer */
+	}
+
+	if (hw->rx_count >= hw->len) {
+		/* transfer completed successfully */
+		au1550_spi_mask_ack_all(hw);
+		complete(&hw->master_done);
+	}
+	return IRQ_HANDLED;
+}
+
+static int au1550_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
+{
+	struct au1550_spi *hw = spi_master_get_devdata(spi->master);
+	return hw->txrx_bufs(spi, t);
+}
+
+static irqreturn_t au1550_spi_irq(int irq, void *dev)
+{
+	struct au1550_spi *hw = dev;
+	return hw->irq_callback(hw);
+}
+
+static void au1550_spi_bits_handlers_set(struct au1550_spi *hw, int bpw)
+{
+	if (bpw <= 8) {
+		if (hw->usedma) {
+			hw->txrx_bufs = &au1550_spi_dma_txrxb;
+			hw->irq_callback = &au1550_spi_dma_irq_callback;
+		} else {
+			hw->rx_word = &au1550_spi_rx_word_8;
+			hw->tx_word = &au1550_spi_tx_word_8;
+			hw->txrx_bufs = &au1550_spi_pio_txrxb;
+			hw->irq_callback = &au1550_spi_pio_irq_callback;
+		}
+	} else if (bpw <= 16) {
+		hw->rx_word = &au1550_spi_rx_word_16;
+		hw->tx_word = &au1550_spi_tx_word_16;
+		hw->txrx_bufs = &au1550_spi_pio_txrxb;
+		hw->irq_callback = &au1550_spi_pio_irq_callback;
+	} else {
+		hw->rx_word = &au1550_spi_rx_word_32;
+		hw->tx_word = &au1550_spi_tx_word_32;
+		hw->txrx_bufs = &au1550_spi_pio_txrxb;
+		hw->irq_callback = &au1550_spi_pio_irq_callback;
+	}
+}
+
+static void au1550_spi_setup_psc_as_spi(struct au1550_spi *hw)
+{
+	u32 stat, cfg;
+
+	/* set up the PSC for SPI mode */
+	hw->regs->psc_ctrl = PSC_CTRL_DISABLE;
+	wmb(); /* drain writebuffer */
+	hw->regs->psc_sel = PSC_SEL_PS_SPIMODE;
+	wmb(); /* drain writebuffer */
+
+	hw->regs->psc_spicfg = 0;
+	wmb(); /* drain writebuffer */
+
+	hw->regs->psc_ctrl = PSC_CTRL_ENABLE;
+	wmb(); /* drain writebuffer */
+
+	do {
+		stat = hw->regs->psc_spistat;
+		wmb(); /* drain writebuffer */
+	} while ((stat & PSC_SPISTAT_SR) == 0);
+
+
+	cfg = hw->usedma ? 0 : PSC_SPICFG_DD_DISABLE;
+	cfg |= PSC_SPICFG_SET_LEN(8);
+	cfg |= PSC_SPICFG_RT_FIFO8 | PSC_SPICFG_TT_FIFO8;
+	/* use minimal allowed brg and div values as initial setting: */
+	cfg |= PSC_SPICFG_SET_BAUD(4) | PSC_SPICFG_SET_DIV(0);
+
+#ifdef AU1550_SPI_DEBUG_LOOPBACK
+	cfg |= PSC_SPICFG_LB;
+#endif
+
+	hw->regs->psc_spicfg = cfg;
+	wmb(); /* drain writebuffer */
+
+	au1550_spi_mask_ack_all(hw);
+
+	hw->regs->psc_spicfg |= PSC_SPICFG_DE_ENABLE;
+	wmb(); /* drain writebuffer */
+
+	do {
+		stat = hw->regs->psc_spistat;
+		wmb(); /* drain writebuffer */
+	} while ((stat & PSC_SPISTAT_DR) == 0);
+
+	au1550_spi_reset_fifos(hw);
+}
+
+
+static int au1550_spi_probe(struct platform_device *pdev)
+{
+	struct au1550_spi *hw;
+	struct spi_master *master;
+	struct resource *r;
+	int err = 0;
+
+	master = spi_alloc_master(&pdev->dev, sizeof(struct au1550_spi));
+	if (master == NULL) {
+		dev_err(&pdev->dev, "No memory for spi_master\n");
+		err = -ENOMEM;
+		goto err_nomem;
+	}
+
+	/* the spi->mode bits understood by this driver: */
+	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_LSB_FIRST;
+	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 24);
+
+	hw = spi_master_get_devdata(master);
+
+	hw->master = master;
+	hw->pdata = dev_get_platdata(&pdev->dev);
+	hw->dev = &pdev->dev;
+
+	if (hw->pdata == NULL) {
+		dev_err(&pdev->dev, "No platform data supplied\n");
+		err = -ENOENT;
+		goto err_no_pdata;
+	}
+
+	r = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!r) {
+		dev_err(&pdev->dev, "no IRQ\n");
+		err = -ENODEV;
+		goto err_no_iores;
+	}
+	hw->irq = r->start;
+
+	hw->usedma = 0;
+	r = platform_get_resource(pdev, IORESOURCE_DMA, 0);
+	if (r) {
+		hw->dma_tx_id = r->start;
+		r = platform_get_resource(pdev, IORESOURCE_DMA, 1);
+		if (r) {
+			hw->dma_rx_id = r->start;
+			if (usedma && ddma_memid) {
+				if (pdev->dev.dma_mask == NULL)
+					dev_warn(&pdev->dev, "no dma mask\n");
+				else
+					hw->usedma = 1;
+			}
+		}
+	}
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r) {
+		dev_err(&pdev->dev, "no mmio resource\n");
+		err = -ENODEV;
+		goto err_no_iores;
+	}
+
+	hw->ioarea = request_mem_region(r->start, sizeof(psc_spi_t),
+					pdev->name);
+	if (!hw->ioarea) {
+		dev_err(&pdev->dev, "Cannot reserve iomem region\n");
+		err = -ENXIO;
+		goto err_no_iores;
+	}
+
+	hw->regs = (psc_spi_t __iomem *)ioremap(r->start, sizeof(psc_spi_t));
+	if (!hw->regs) {
+		dev_err(&pdev->dev, "cannot ioremap\n");
+		err = -ENXIO;
+		goto err_ioremap;
+	}
+
+	platform_set_drvdata(pdev, hw);
+
+	init_completion(&hw->master_done);
+
+	hw->bitbang.master = hw->master;
+	hw->bitbang.setup_transfer = au1550_spi_setupxfer;
+	hw->bitbang.chipselect = au1550_spi_chipsel;
+	hw->bitbang.txrx_bufs = au1550_spi_txrx_bufs;
+
+	if (hw->usedma) {
+		hw->dma_tx_ch = au1xxx_dbdma_chan_alloc(ddma_memid,
+			hw->dma_tx_id, NULL, (void *)hw);
+		if (hw->dma_tx_ch == 0) {
+			dev_err(&pdev->dev,
+				"Cannot allocate tx dma channel\n");
+			err = -ENXIO;
+			goto err_no_txdma;
+		}
+		au1xxx_dbdma_set_devwidth(hw->dma_tx_ch, 8);
+		if (au1xxx_dbdma_ring_alloc(hw->dma_tx_ch,
+			AU1550_SPI_DBDMA_DESCRIPTORS) == 0) {
+			dev_err(&pdev->dev,
+				"Cannot allocate tx dma descriptors\n");
+			err = -ENXIO;
+			goto err_no_txdma_descr;
+		}
+
+
+		hw->dma_rx_ch = au1xxx_dbdma_chan_alloc(hw->dma_rx_id,
+			ddma_memid, NULL, (void *)hw);
+		if (hw->dma_rx_ch == 0) {
+			dev_err(&pdev->dev,
+				"Cannot allocate rx dma channel\n");
+			err = -ENXIO;
+			goto err_no_rxdma;
+		}
+		au1xxx_dbdma_set_devwidth(hw->dma_rx_ch, 8);
+		if (au1xxx_dbdma_ring_alloc(hw->dma_rx_ch,
+			AU1550_SPI_DBDMA_DESCRIPTORS) == 0) {
+			dev_err(&pdev->dev,
+				"Cannot allocate rx dma descriptors\n");
+			err = -ENXIO;
+			goto err_no_rxdma_descr;
+		}
+
+		err = au1550_spi_dma_rxtmp_alloc(hw,
+			AU1550_SPI_DMA_RXTMP_MINSIZE);
+		if (err < 0) {
+			dev_err(&pdev->dev,
+				"Cannot allocate initial rx dma tmp buffer\n");
+			goto err_dma_rxtmp_alloc;
+		}
+	}
+
+	au1550_spi_bits_handlers_set(hw, 8);
+
+	err = request_irq(hw->irq, au1550_spi_irq, 0, pdev->name, hw);
+	if (err) {
+		dev_err(&pdev->dev, "Cannot claim IRQ\n");
+		goto err_no_irq;
+	}
+
+	master->bus_num = pdev->id;
+	master->num_chipselect = hw->pdata->num_chipselect;
+
+	/*
+	 *  precompute valid range for spi freq - from au1550 datasheet:
+	 *    psc_tempclk = psc_mainclk / (2 << DIV)
+	 *    spiclk = psc_tempclk / (2 * (BRG + 1))
+	 *    BRG valid range is 4..63
+	 *    DIV valid range is 0..3
+	 *  round the min and max frequencies to values that would still
+	 *  produce valid brg and div
+	 */
+	{
+		int min_div = (2 << 0) * (2 * (4 + 1));
+		int max_div = (2 << 3) * (2 * (63 + 1));
+		master->max_speed_hz = hw->pdata->mainclk_hz / min_div;
+		master->min_speed_hz =
+				hw->pdata->mainclk_hz / (max_div + 1) + 1;
+	}
+
+	au1550_spi_setup_psc_as_spi(hw);
+
+	err = spi_bitbang_start(&hw->bitbang);
+	if (err) {
+		dev_err(&pdev->dev, "Failed to register SPI master\n");
+		goto err_register;
+	}
+
+	dev_info(&pdev->dev,
+		"spi master registered: bus_num=%d num_chipselect=%d\n",
+		master->bus_num, master->num_chipselect);
+
+	return 0;
+
+err_register:
+	free_irq(hw->irq, hw);
+
+err_no_irq:
+	au1550_spi_dma_rxtmp_free(hw);
+
+err_dma_rxtmp_alloc:
+err_no_rxdma_descr:
+	if (hw->usedma)
+		au1xxx_dbdma_chan_free(hw->dma_rx_ch);
+
+err_no_rxdma:
+err_no_txdma_descr:
+	if (hw->usedma)
+		au1xxx_dbdma_chan_free(hw->dma_tx_ch);
+
+err_no_txdma:
+	iounmap((void __iomem *)hw->regs);
+
+err_ioremap:
+	release_mem_region(r->start, sizeof(psc_spi_t));
+
+err_no_iores:
+err_no_pdata:
+	spi_master_put(hw->master);
+
+err_nomem:
+	return err;
+}
+
+static int au1550_spi_remove(struct platform_device *pdev)
+{
+	struct au1550_spi *hw = platform_get_drvdata(pdev);
+
+	dev_info(&pdev->dev, "spi master remove: bus_num=%d\n",
+		hw->master->bus_num);
+
+	spi_bitbang_stop(&hw->bitbang);
+	free_irq(hw->irq, hw);
+	iounmap((void __iomem *)hw->regs);
+	release_mem_region(hw->ioarea->start, sizeof(psc_spi_t));
+
+	if (hw->usedma) {
+		au1550_spi_dma_rxtmp_free(hw);
+		au1xxx_dbdma_chan_free(hw->dma_rx_ch);
+		au1xxx_dbdma_chan_free(hw->dma_tx_ch);
+	}
+
+	spi_master_put(hw->master);
+	return 0;
+}
+
+/* work with hotplug and coldplug */
+MODULE_ALIAS("platform:au1550-spi");
+
+static struct platform_driver au1550_spi_drv = {
+	.probe = au1550_spi_probe,
+	.remove = au1550_spi_remove,
+	.driver = {
+		.name = "au1550-spi",
+	},
+};
+
+static int __init au1550_spi_init(void)
+{
+	/*
+	 * create memory device with 8 bits dev_devwidth
+	 * needed for proper byte ordering to spi fifo
+	 */
+	switch (alchemy_get_cputype()) {
+	case ALCHEMY_CPU_AU1550:
+	case ALCHEMY_CPU_AU1200:
+	case ALCHEMY_CPU_AU1300:
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	if (usedma) {
+		ddma_memid = au1xxx_ddma_add_device(&au1550_spi_mem_dbdev);
+		if (!ddma_memid)
+			printk(KERN_ERR "au1550-spi: cannot add memory"
+					"dbdma device\n");
+	}
+	return platform_driver_register(&au1550_spi_drv);
+}
+module_init(au1550_spi_init);
+
+static void __exit au1550_spi_exit(void)
+{
+	if (usedma && ddma_memid)
+		au1xxx_ddma_del_device(ddma_memid);
+	platform_driver_unregister(&au1550_spi_drv);
+}
+module_exit(au1550_spi_exit);
+
+MODULE_DESCRIPTION("Au1550 PSC SPI Driver");
+MODULE_AUTHOR("Jan Nikitenko <jan.nikitenko@gmail.com>");
+MODULE_LICENSE("GPL");