linux-kernel - Re: [RESEND][PATCH] tpm: read burstcount from TPM

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Date:	Fri, 1 Jul 2016 11:45:45 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	apronin@...omium.org
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
Subject: Re: [RESEND][PATCH] tpm: read burstcount from TPM_STS in one 32-bit
 transaction

On Fri, Jul 01, 2016 at 11:43:23AM +0300, Jarkko Sakkinen wrote:
> On Thu, Jun 30, 2016 at 10:25:43AM -0700, apronin@...omium.org wrote:
> > 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>
> 
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

Applied to my master branch.

/Jarkko

> 
> /Jarkko
> 
> > ---
> > 
> > No changes. 
> > Re-sending to tpmdd-devel member-only list after subscribing.
> > 
> >  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
> >