Re: [PATCH 3/5] tpm_tis_spi: Check correct byte for wait state indicator

Christophe Ricard
2017-02-17T05:09:37Z

That's is correct, this is a mistake on my side and never saw it :-(.

I guess it was possibly leading to "waste" at least 1 wait state on some
TPMs.

Wouldn't it be better to merge that with #1 and update the comment
consequently?

On 16/02/2017 08:08, Peter Huewe wrote:
> Wait states are signaled in the last byte received from the TPM in
> response to the header, not the first byte. Check rx_buf[3] instead of
> rx_buf[0].
>
> Cc: <stable@vger.kernel.org>
> Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
> Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
> Signed-off-by: Peter Huewe <peter.huewe@infineon.com>
> ---
> drivers/char/tpm/tpm_tis_spi.c | 40 +++++++++++++++++++++-------------------
> 1 file changed, 21 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c
> index d782b9974c14..16938e2253d2 100644
> --- a/drivers/char/tpm/tpm_tis_spi.c
> +++ b/drivers/char/tpm/tpm_tis_spi.c
> @@ -60,7 +60,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u8 len,
> u8 *buffer, u8 direction)
> {
> struct tpm_tis_spi_phy *phy = to_tpm_tis_spi_phy(data);
> - int ret, i;
> + int ret;
> struct spi_message m;
> struct spi_transfer spi_xfer = {
> .tx_buf = phy->tx_buf,
> @@ -85,25 +85,27 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u8 len,
> if (ret < 0)
> goto exit;
>
> - phy->tx_buf[0] = 0;
> -
> - /* According to TCG PTP specification, if there is no TPM present at
> - * all, then the design has a weak pull-up on MISO. If a TPM is not
> - * present, a pull-up on MISO means that the SB controller sees a 1,
> - * and will latch in 0xFF on the read.
> - */
> - for (i = 0; (phy->rx_buf[0] & 0x01) == 0 && i < TPM_RETRY; i++) {
> - spi_xfer.len = 1;
> - spi_message_init(&m);
> - spi_message_add_tail(&spi_xfer, &m);
> - ret = spi_sync_locked(phy->spi_device, &m);
> - if (ret < 0)
> + if ((phy->rx_buf[3] & 0x01) == 0) {
> + // handle SPI wait states
> + int i;
> +
> + phy->tx_buf[0] = 0;
> +
> + for (i = 0; i < TPM_RETRY; i++) {
> + spi_xfer.len = 1;
> + spi_message_init(&m);
> + spi_message_add_tail(&spi_xfer, &m);
> + ret = spi_sync_locked(phy->spi_device, &m);
> + if (ret < 0)
> + goto exit;
> + if (phy->rx_buf[0] & 0x01)
> + break;
> + }
> +
> + if (i == TPM_RETRY) {
> + ret = -ETIMEDOUT;
> goto exit;
> - }
> -
> - if (i == TPM_RETRY) {
> - ret = -ETIMEDOUT;
> - goto exit;
> + }
> }
>
> spi_xfer.cs_change = 0;