Am 17. Februar 2017 06:09:30 MEZ schrieb Christophe Ricard [off-list ref]:

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.

Unfortunately the 1 for indicating end of waitstates does only appear once so it actually rendered the driver non-functional - atleast with our tpms.

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

Yes, that's what I wanted to express in the cover letter, logically it makes sense to squash #1 and #3 - but reviewing it merged with #1 is quite hard since it "obfuscates" the problem - since too much stuff moves around.
That's why I decided to split it - for easier review.

Peter

On 16/02/2017 08:08, Peter Huewe wrote:

quoted

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

quoted

rx_buf[0].

Cc: <redacted>
Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
Signed-off-by: Alexander Steffen <redacted>
Signed-off-by: Peter Huewe <redacted>
---
  drivers/char/tpm/tpm_tis_spi.c | 40

+++++++++++++++++++++-------------------

quoted

  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

quoted

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,

quoted

  				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,

quoted

  	if (ret < 0)
  		goto exit;
  
-	phy->tx_buf[0] = 0;
-
-	/* According to TCG PTP specification, if there is no TPM present

at

quoted

-	 * 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,

quoted

-	 * 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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