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

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