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Date: Wed, 29 Jun 2016 20:49:04 -0700 From: apronin@...omium.org To: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> Cc: Peter Huewe <peterhuewe@....de>, Marcel Selhorst <tpmdd@...horst.net>, Jason Gunthorpe <jgunthorpe@...idianresearch.com>, Christophe Ricard <christophe.ricard@...il.com>, tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, Andrey Pronin <apronin@...omium.org> Subject: [PATCH] tpm: read burstcount from TPM_STS in one 32-bit transaction From: Andrey Pronin <apronin@...omium.org> 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. Signed-off-by: Andrey Pronin <apronin@...omium.org> --- drivers/char/tpm/tpm_tis_core.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c index 03a06b3..8110b52 100644 --- a/drivers/char/tpm/tpm_tis_core.c +++ b/drivers/char/tpm/tpm_tis_core.c @@ -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); -- 2.6.6
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