From: Ivan Bornyakov <i.bornyakov@metrotek.ru>

Date: Fri, 30 Dec 2022 12:29:20 +0300

Subject: [PATCH] fpga: microchip-spi: move SPI I/O buffers out of stack

References: bsc#1012628

Patch-mainline: 6.2.3

Git-commit: 1da53d23a41c5f77963984d8da5623ed56918ada

[ Upstream commit 1da53d23a41c5f77963984d8da5623ed56918ada ]

As spi-summary doc says:

 > I/O buffers use the usual Linux rules, and must be DMA-safe.

 > You'd normally allocate them from the heap or free page pool.

 > Don't use the stack, or anything that's declared "static".

Replace spi_write() with spi_write_then_read(), which is dma-safe for

on-stack buffers. Use cacheline aligned buffers for transfers used in

spi_sync_transfer().

Although everything works OK with stack-located I/O buffers, better

follow the doc to be safe.

Fixes: 5f8d4a900830 ("fpga: microchip-spi: add Microchip MPF FPGA manager")

Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>

Acked-by: Conor Dooley <conor.dooley@microchip.com>

Acked-by: Xu Yilun <yilun.xu@intel.com>

Link: https://lore.kernel.org/r/20221230092922.18822-2-i.bornyakov@metrotek.ru

Signed-off-by: Xu Yilun <yilun.xu@intel.com>

Signed-off-by: Sasha Levin <sashal@kernel.org>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 drivers/fpga/microchip-spi.c | 93 ++++++++++++++++++------------------

 1 file changed, 47 insertions(+), 46 deletions(-)

diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c

index 7436976e..bb69f5be 100644

--- a/drivers/fpga/microchip-spi.c

+++ b/drivers/fpga/microchip-spi.c

@@ -42,46 +42,55 @@

 struct mpf_priv {

 	struct spi_device *spi;

 	bool program_mode;

+	u8 tx __aligned(ARCH_KMALLOC_MINALIGN);

+	u8 rx;

 };

-static int mpf_read_status(struct spi_device *spi)

+static int mpf_read_status(struct mpf_priv *priv)

 {

-	u8 status = 0, status_command = MPF_SPI_READ_STATUS;

-	struct spi_transfer xfers[2] = { 0 };

-	int ret;

-

 	/*

 	 * HW status is returned on MISO in the first byte after CS went

 	 * active. However, first reading can be inadequate, so we submit

 	 * two identical SPI transfers and use result of the later one.

 	 */

-	xfers[0].tx_buf = &status_command;

-	xfers[1].tx_buf = &status_command;

-	xfers[0].rx_buf = &status;

-	xfers[1].rx_buf = &status;

-	xfers[0].len = 1;

-	xfers[1].len = 1;

-	xfers[0].cs_change = 1;

+	struct spi_transfer xfers[2] = {

+		{

+			.tx_buf = &priv->tx,

+			.rx_buf = &priv->rx,

+			.len = 1,

+			.cs_change = 1,

+		}, {

+			.tx_buf = &priv->tx,

+			.rx_buf = &priv->rx,

+			.len = 1,

+		},

+	};

+	u8 status;

+	int ret;

+

+	priv->tx = MPF_SPI_READ_STATUS;

+

+	ret = spi_sync_transfer(priv->spi, xfers, 2);

+	if (ret)

+		return ret;

-	ret = spi_sync_transfer(spi, xfers, 2);

+	status = priv->rx;

 	if ((status & MPF_STATUS_SPI_VIOLATION) ||

 	    (status & MPF_STATUS_SPI_ERROR))

-		ret = -EIO;

+		return -EIO;

-	return ret ? : status;

+	return status;

 }

 static enum fpga_mgr_states mpf_ops_state(struct fpga_manager *mgr)

 {

 	struct mpf_priv *priv = mgr->priv;

-	struct spi_device *spi;

 	bool program_mode;

 	int status;

-	spi = priv->spi;

 	program_mode = priv->program_mode;

-	status = mpf_read_status(spi);

+	status = mpf_read_status(priv);

 	if (!program_mode && !status)

 		return FPGA_MGR_STATE_OPERATING;

@@ -186,12 +195,12 @@ static int mpf_ops_parse_header(struct fpga_manager *mgr,

 }

 /* Poll HW status until busy bit is cleared and mask bits are set. */

-static int mpf_poll_status(struct spi_device *spi, u8 mask)

+static int mpf_poll_status(struct mpf_priv *priv, u8 mask)

 {

 	int status, retries = MPF_STATUS_POLL_RETRIES;

 	while (retries--) {

-		status = mpf_read_status(spi);

+		status = mpf_read_status(priv);

 		if (status < 0)

 			return status;

@@ -205,32 +214,32 @@ static int mpf_poll_status(struct spi_device *spi, u8 mask)

 	return -EBUSY;

 }

-static int mpf_spi_write(struct spi_device *spi, const void *buf, size_t buf_size)

+static int mpf_spi_write(struct mpf_priv *priv, const void *buf, size_t buf_size)

 {

-	int status = mpf_poll_status(spi, 0);

+	int status = mpf_poll_status(priv, 0);

 	if (status < 0)

 		return status;

-	return spi_write(spi, buf, buf_size);

+	return spi_write_then_read(priv->spi, buf, buf_size, NULL, 0);

 }

-static int mpf_spi_write_then_read(struct spi_device *spi,

+static int mpf_spi_write_then_read(struct mpf_priv *priv,

 				   const void *txbuf, size_t txbuf_size,

 				   void *rxbuf, size_t rxbuf_size)

 {

 	const u8 read_command[] = { MPF_SPI_READ_DATA };

 	int ret;

-	ret = mpf_spi_write(spi, txbuf, txbuf_size);

+	ret = mpf_spi_write(priv, txbuf, txbuf_size);

 	if (ret)

 		return ret;

-	ret = mpf_poll_status(spi, MPF_STATUS_READY);

+	ret = mpf_poll_status(priv, MPF_STATUS_READY);

 	if (ret < 0)

 		return ret;

-	return spi_write_then_read(spi, read_command, sizeof(read_command),

+	return spi_write_then_read(priv->spi, read_command, sizeof(read_command),

 				   rxbuf, rxbuf_size);

 }

@@ -242,7 +251,6 @@ static int mpf_ops_write_init(struct fpga_manager *mgr,

 	const u8 isc_en_command[] = { MPF_SPI_ISC_ENABLE };

 	struct mpf_priv *priv = mgr->priv;

 	struct device *dev = &mgr->dev;

-	struct spi_device *spi;

 	u32 isc_ret = 0;

 	int ret;

@@ -251,9 +259,7 @@ static int mpf_ops_write_init(struct fpga_manager *mgr,

 		return -EOPNOTSUPP;

 	}

-	spi = priv->spi;

-

-	ret = mpf_spi_write_then_read(spi, isc_en_command, sizeof(isc_en_command),

+	ret = mpf_spi_write_then_read(priv, isc_en_command, sizeof(isc_en_command),

 				      &isc_ret, sizeof(isc_ret));

 	if (ret || isc_ret) {

 		dev_err(dev, "Failed to enable ISC: spi_ret %d, isc_ret %u\n",

@@ -261,7 +267,7 @@ static int mpf_ops_write_init(struct fpga_manager *mgr,

 		return -EFAULT;

 	}

-	ret = mpf_spi_write(spi, program_mode, sizeof(program_mode));

+	ret = mpf_spi_write(priv, program_mode, sizeof(program_mode));

 	if (ret) {

 		dev_err(dev, "Failed to enter program mode: %d\n", ret);

 		return ret;

@@ -274,11 +280,9 @@ static int mpf_ops_write_init(struct fpga_manager *mgr,

 static int mpf_ops_write(struct fpga_manager *mgr, const char *buf, size_t count)

 {

-	u8 spi_frame_command[] = { MPF_SPI_FRAME };

 	struct spi_transfer xfers[2] = { 0 };

 	struct mpf_priv *priv = mgr->priv;

 	struct device *dev = &mgr->dev;

-	struct spi_device *spi;

 	int ret, i;

 	if (count % MPF_SPI_FRAME_SIZE) {

@@ -287,18 +291,18 @@ static int mpf_ops_write(struct fpga_manager *mgr, const char *buf, size_t count

 		return -EINVAL;

 	}

-	spi = priv->spi;

-

-	xfers[0].tx_buf = spi_frame_command;

-	xfers[0].len = sizeof(spi_frame_command);

+	xfers[0].tx_buf = &priv->tx;

+	xfers[0].len = 1;

 	for (i = 0; i < count / MPF_SPI_FRAME_SIZE; i++) {

 		xfers[1].tx_buf = buf + i * MPF_SPI_FRAME_SIZE;

 		xfers[1].len = MPF_SPI_FRAME_SIZE;

-		ret = mpf_poll_status(spi, 0);

-		if (ret >= 0)

-			ret = spi_sync_transfer(spi, xfers, ARRAY_SIZE(xfers));

+		ret = mpf_poll_status(priv, 0);

+		if (ret >= 0) {

+			priv->tx = MPF_SPI_FRAME;

+			ret = spi_sync_transfer(priv->spi, xfers, ARRAY_SIZE(xfers));

+		}

 		if (ret) {

 			dev_err(dev, "Failed to write bitstream frame %d/%zu\n",

@@ -317,12 +321,9 @@ static int mpf_ops_write_complete(struct fpga_manager *mgr,

 	const u8 release_command[] = { MPF_SPI_RELEASE };

 	struct mpf_priv *priv = mgr->priv;

 	struct device *dev = &mgr->dev;

-	struct spi_device *spi;

 	int ret;

-	spi = priv->spi;

-

-	ret = mpf_spi_write(spi, isc_dis_command, sizeof(isc_dis_command));

+	ret = mpf_spi_write(priv, isc_dis_command, sizeof(isc_dis_command));

 	if (ret) {

 		dev_err(dev, "Failed to disable ISC: %d\n", ret);

 		return ret;

@@ -330,7 +331,7 @@ static int mpf_ops_write_complete(struct fpga_manager *mgr,

 	usleep_range(1000, 2000);

-	ret = mpf_spi_write(spi, release_command, sizeof(release_command));

+	ret = mpf_spi_write(priv, release_command, sizeof(release_command));

 	if (ret) {

 		dev_err(dev, "Failed to exit program mode: %d\n", ret);

 		return ret;

-- 

2.35.3