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Message-ID: <Y6xVyCt5tXwnKhfw@spud>
Date: Wed, 28 Dec 2022 14:42:16 +0000
From: Conor Dooley <conor@...nel.org>
To: Ivan Bornyakov <i.bornyakov@...rotek.ru>
Cc: Conor Dooley <conor.dooley@...rochip.com>,
Moritz Fischer <mdf@...nel.org>, Wu Hao <hao.wu@...el.com>,
Xu Yilun <yilun.xu@...el.com>, Tom Rix <trix@...hat.com>,
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org,
system@...rotek.ru
Subject: Re: [PATCH v3 1/3] fpga: microchip-spi: move SPI I/O buffers out of
stack
Hey Ivan,
Given the time of year, I don't have my proper setup to actually go an
test this (or the other patches).
On Tue, Dec 27, 2022 at 01:04:48PM +0300, Ivan Bornyakov wrote:
> 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 allocated 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@...rotek.ru>
The changes look fine though...
Acked-by: Conor Dooley <conor.dooley@...rochip.com>
Thanks,
Conor.
> ---
> 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 7436976ea904..e72fedd93a27 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 __aligned(ARCH_KMALLOC_MINALIGN);
> };
>
> -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;
> --
> 2.38.2
>
>
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