linux-kernel - Re: [tpmdd-devel] [PATCH v2 2/3] tpm_crb: encapsulate crb_wait_for_reg

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Date:   Tue, 6 Dec 2016 20:38:40 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     "Winkler, Tomas" <tomas.winkler@...el.com>
Cc:     Peter Huewe <peterhuewe@....de>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "moderated list:TPM DEVICE DRIVER" 
        <tpmdd-devel@...ts.sourceforge.net>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [tpmdd-devel] [PATCH v2 2/3] tpm_crb: encapsulate
 crb_wait_for_reg_32

On Mon, Dec 05, 2016 at 09:34:50PM +0000, Winkler, Tomas wrote:
> > CC linux-security-module
> > 
> > On Sat, Dec 03, 2016 at 07:52:12PM +0200, Jarkko Sakkinen wrote:
> > > Encapsulated crb_wait_for_reg32() so that state changes in other CRB
> > > registers than TPM_CRB_CTRL_REQ_x can be waited.
> > >
> > > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > > ---
> > >  drivers/char/tpm/tpm_crb.c | 37 +++++++++++++++++++++++--------------
> > >  1 file changed, 23 insertions(+), 14 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> > > index 8d81b66..f986d02 100644
> > > --- a/drivers/char/tpm/tpm_crb.c
> > > +++ b/drivers/char/tpm/tpm_crb.c
> > > @@ -121,6 +121,25 @@ static int __maybe_unused crb_go_idle(struct
> > device *dev, struct crb_priv *priv)
> > >  	return 0;
> > >  }
> > >
> > > +static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
> > > +				unsigned long timeout)
> > > +{
> > > +	ktime_t start;
> > > +	ktime_t stop;
> > > +
> > > +	start = ktime_get();
> > > +	stop = ktime_add(start, ms_to_ktime(timeout));
> > > +
> > > +	do {
> > > +		if ((ioread32(reg) & mask) == value)
> > > +			return true;
> > > +
> > > +		usleep_range(50, 100);
> This was tuned for power management, have you tuned it for locality? 

We don't want million different wait functions and the current values
work without issues for locale.

/Jarkko

> > > +	} while (ktime_before(ktime_get(), stop));
> > > +
> > > +	return false;
> > > +}
> > > +
> > >  /**
> > >   * crb_cmd_ready - request tpm crb device to enter ready state
> > >   *
> > > @@ -138,24 +157,14 @@ static int __maybe_unused crb_go_idle(struct
> > > device *dev, struct crb_priv *priv)  static int __maybe_unused
> > crb_cmd_ready(struct device *dev,
> > >  					struct crb_priv *priv)
> > >  {
> > > -	ktime_t stop, start;
> > > -	u32 req;
> > > -
> > >  	if (priv->flags & CRB_FL_ACPI_START)
> > >  		return 0;
> > >
> > >  	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);
> > > -
> > > -	start = ktime_get();
> > > -	stop = ktime_add(start, ms_to_ktime(TPM2_TIMEOUT_C));
> > > -	do {
> > > -		req = ioread32(&priv->regs_t->ctrl_req);
> > > -		if (!(req & CRB_CTRL_REQ_CMD_READY))
> > > -			return 0;
> > > -		usleep_range(50, 100);
> > > -	} while (ktime_before(ktime_get(), stop));
> > > -
> > > -	if (ioread32(&priv->regs_t->ctrl_req) & CRB_CTRL_REQ_CMD_READY)
> > {
> > > +	if (!crb_wait_for_reg_32(&priv->regs_t->ctrl_req,
> > > +				 CRB_CTRL_REQ_CMD_READY /* mask */,
> > > +				 0, /* value */
> > > +				 TPM2_TIMEOUT_C)) {
> > >  		dev_warn(dev, "cmdReady timed out\n");
> > >  		return -ETIME;
> > >  	}
> > > --
> > > 2.9.3
> > >
> > 
> > ------------------------------------------------------------------------------
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