On Fri, Aug 18, 2017 at 02:14:57PM +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.
>
> A single buffer is sufficient for both tx and rx, since bytes that have
> already been sent are not used anymore and can safely be overwritten with
> the received bytes. 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@xxxxxxxxxxxxxxx
> Signed-off-by: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx>
90% of this patch is about merging the buffers and 10% is the bug fix
that you even want to stable, right?
So please create a patch that does the fix without merging the buffers.
In this form this is pain to backport to stable.
/Jarkko
> ---
> v2: Updated commit message with more explanations.
>
> drivers/char/tpm/tpm_tis_spi.c | 32 ++++++++++++++++++--------------
> 1 file changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index 88fe72a..5321245 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] = direction | (transfer_len - 1);
> - phy->tx_buf[1] = 0xd4;
> - phy->tx_buf[2] = addr >> 8;
> - phy->tx_buf[3] = addr;
> + phy->iobuf[0] = direction | (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;
> }
>
> @@ -115,10 +113,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
>
> if (direction) {
> spi_xfer.tx_buf = NULL;
> - spi_xfer.rx_buf = buffer;
> } else {
> - spi_xfer.tx_buf = buffer;
> spi_xfer.rx_buf = NULL;
> + memcpy(phy->iobuf, buffer, transfer_len);
> }
>
> spi_message_init(&m);
> @@ -127,6 +124,9 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
> if (ret < 0)
> goto exit;
>
> + if (direction)
> + memcpy(buffer, phy->iobuf, transfer_len);
> +
> len -= transfer_len;
> buffer += transfer_len;
> }
> @@ -194,6 +194,10 @@ 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
>