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SubjectRe: [PATCH v4] tpm_tis_spi: Use DMA-safe memory for SPI transfers
On Mon, Sep 11, 2017 at 12:26:52PM +0200, Alexander Steffen wrote:
> The buffers used as tx_buf/rx_buf in a SPI transfer need to be DMA-safe.
> This cannot be guaranteed for the buffers passed to tpm_tis_spi_read_bytes
> and tpm_tis_spi_write_bytes. Therefore, we need to use our own DMA-safe
> buffer and copy the data to/from it.
>
> The buffer needs to be allocated separately, to ensure that it is
> cacheline-aligned and not shared with other data, so that DMA can work
> correctly.
>
> Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
> ---
> v2:
> - Updated commit message with more explanations.
> v3:
> - Split into two patches, one for making the buffers DMA-safe and another
> for using only a single buffer.
> v4:
> - Back to one patch, to fix conflicts with new const buffers.
>
> drivers/char/tpm/tpm_tis_spi.c | 45 +++++++++++++++++++++++++-----------------
> 1 file changed, 27 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index e49f5b9..8ab0bd8 100644
> --- a/drivers/char/tpm/tpm_tis_spi.c
> +++ b/drivers/char/tpm/tpm_tis_spi.c
> @@ -46,9 +46,7 @@
> struct tpm_tis_spi_phy {
> struct tpm_tis_data priv;
> struct spi_device *spi_device;
> -
> - u8 tx_buf[4];
> - u8 rx_buf[4];
> + u8 *iobuf;
> };
>
> static inline struct tpm_tis_spi_phy *to_tpm_tis_spi_phy(struct tpm_tis_data *data)
> @@ -71,14 +69,14 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> while (len) {
> transfer_len = min_t(u16, len, MAX_SPI_FRAMESIZE);
>
> - phy->tx_buf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
> - phy->tx_buf[1] = 0xd4;
> - phy->tx_buf[2] = addr >> 8;
> - phy->tx_buf[3] = addr;
> + phy->iobuf[0] = (in ? 0x80 : 0) | (transfer_len - 1);
> + phy->iobuf[1] = 0xd4;
> + phy->iobuf[2] = addr >> 8;
> + phy->iobuf[3] = addr;
>
> memset(&spi_xfer, 0, sizeof(spi_xfer));
> - spi_xfer.tx_buf = phy->tx_buf;
> - spi_xfer.rx_buf = phy->rx_buf;
> + spi_xfer.tx_buf = phy->iobuf;
> + spi_xfer.rx_buf = phy->iobuf;
> spi_xfer.len = 4;
> spi_xfer.cs_change = 1;
>
> @@ -88,9 +86,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> if (ret < 0)
> goto exit;
>
> - if ((phy->rx_buf[3] & 0x01) == 0) {
> + if ((phy->iobuf[3] & 0x01) == 0) {
> // handle SPI wait states
> - phy->tx_buf[0] = 0;
> + phy->iobuf[0] = 0;
>
> for (i = 0; i < TPM_RETRY; i++) {
> spi_xfer.len = 1;
> @@ -99,7 +97,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> ret = spi_sync_locked(phy->spi_device, &m);
> if (ret < 0)
> goto exit;
> - if (phy->rx_buf[0] & 0x01)
> + if (phy->iobuf[0] & 0x01)
> break;
> }
>
> @@ -112,8 +110,14 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> spi_xfer.cs_change = 0;
> spi_xfer.len = transfer_len;
> spi_xfer.delay_usecs = 5;
> - spi_xfer.tx_buf = out;
> - spi_xfer.rx_buf = in;
> +
> + if (in) {
> + spi_xfer.tx_buf = NULL;
> + } else if (out) {
> + spi_xfer.rx_buf = NULL;
> + memcpy(phy->iobuf, out, transfer_len);
> + out += transfer_len;
> + }
>
> spi_message_init(&m);
> spi_message_add_tail(&spi_xfer, &m);
> @@ -121,11 +125,12 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> if (ret < 0)
> goto exit;
>
> - len -= transfer_len;
> - if (in)
> + if (in) {
> + memcpy(in, phy->iobuf, transfer_len);
> in += transfer_len;
> - if (out)
> - out += transfer_len;
> + }
> +
> + len -= transfer_len;
> }
>
> exit:
> @@ -191,6 +196,10 @@ static int tpm_tis_spi_probe(struct spi_device *dev)
>
> phy->spi_device = dev;
>
> + phy->iobuf = devm_kmalloc(&dev->dev, MAX_SPI_FRAMESIZE, GFP_KERNEL);
> + if (!phy->iobuf)
> + return -ENOMEM;
> +
> return tpm_tis_core_init(&dev->dev, &phy->priv, -1, &tpm_spi_phy_ops,
> NULL);
> }
> --
> 2.7.4
>

Great, I swapped to this patch in my master branch. I'm not able to
test it before I'm back to Finland from US (next week).

/Jarkko

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