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tpm: read burstcount from TPM_STS in one 32-bit transaction 

Some chips incorrectly support partial reads from TPM_STS register
at non-zero offsets. Read the entire 32-bits register instead of
making two 8-bit reads to support such devices and reduce the number
of bus transactions when obtaining the burstcount from TPM_STS.

Fixes: 27084efee0 ("tpm: driver for next generation TPM chips")
Signed-off-by: Andrey Pronin <apronin@chromium.org>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
This commit is contained in:
Andrey Pronin 2016-06-30 10:25:43 -07:00 committed by Jarkko Sakkinen
parent 1b0612b040
commit 9754d45e99
1 changed files with 3 additions and 8 deletions
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11
drivers/char/tpm/tpm_tis_core.c
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@ -157,22 +157,17 @@ static int get_burstcount(struct tpm_chip *chip)
struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
unsigned long stop;
int burstcnt, rc;
u8 value;
u32 value;
/* wait for burstcount */
/* which timeout value, spec has 2 answers (c & d) */
stop = jiffies + chip->timeout_d;
do {
rc = tpm_tis_read8(priv, TPM_STS(priv->locality) + 1, &value);
rc = tpm_tis_read32(priv, TPM_STS(priv->locality), &value);
if (rc < 0)
return rc;
burstcnt = value;
rc = tpm_tis_read8(priv, TPM_STS(priv->locality) + 2, &value);
if (rc < 0)
return rc;
burstcnt += value << 8;
burstcnt = (value >> 8) & 0xFFFF;
if (burstcnt)
return burstcnt;
msleep(TPM_TIMEOUT);