fpga: microchip-spi: move SPI I/O buffers out of stack

[ 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>

diff --git a/drivers/fpga/microchip-spi.c b/drivers/fpga/microchip-spi.c
index 7436976..bb69f5b 100644 (file)
--- 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;