linux-kernel - RE: [PATCH v3 1/4] tpm/tpm_crb: implement tpm crb idle state

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Message-ID: <5B8DA87D05A7694D9FA63FD143655C1B542DBC0D@hasmsx108.ger.corp.intel.com>
Date:   Thu, 15 Sep 2016 06:28:27 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC:     "tpmdd-devel@...ts.sourceforge.net" 
        <tpmdd-devel@...ts.sourceforge.net>,
        Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 1/4] tpm/tpm_crb: implement tpm crb idle state

> Subject: Re: [PATCH v3 1/4] tpm/tpm_crb: implement tpm crb idle state
> 
> On Mon, Sep 12, 2016 at 04:04:18PM +0300, Tomas Winkler wrote:
> > The register TPM_CRB_CTRL_REQ_x contains bits goIdle and cmdReady for
> > SW to indicate that the device can enter or should exit the idle state.
> >
> > The legacy ACPI-start (SMI + DMA) based devices do not support these
> > bits and the idle state management is not exposed to the host SW.
> > Thus, this functionality only is enabled only for a CRB start (MMIO)
> > based devices.
> >
> > Based on Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> oringal
> > patch:
> > 'tpm_crb: implement power tpm crb power management'
> >
> >
> > Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> > ---
> > V2: do not export the functions via tpm ops
> > V3: fix lower case corruption; adjust function documentation
> >
> >  drivers/char/tpm/tpm_crb.c | 69
> > ++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 69 insertions(+)
> >
> > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> > index 6e9d1bca712f..b6923a8b3ff7 100644
> > --- a/drivers/char/tpm/tpm_crb.c
> > +++ b/drivers/char/tpm/tpm_crb.c
> > @@ -83,6 +83,75 @@ struct crb_priv {
> >  	u32 cmd_size;
> >  };
> >
> > +/**
> > + * crb_go_idle - request tpm crb device to go the idle state
> > + *
> > + * @dev:  crb device
> > + * @priv: crb private data
> > + *
> > + * Write CRB_CTRL_REQ_GO_IDLE to TPM_CRB_CTRL_REQ
> > + * The device should respond within TIMEOUT_C by clearing the bit.
> > + * Anyhow, we do not wait here as a consequent CMD_READY request
> > + * will be handled correctly even if idle was not completed.
> > + *
> > + * The function does nothing for devices with ACPI-start method.
> > + *
> > + * Return: 0 always
> > + */
> > +static int __maybe_unused crb_go_idle(struct device *dev, struct
> > +crb_priv *priv) {
> > +	if (priv->flags & CRB_FL_ACPI_START)
> > +		return 0;
> > +
> > +	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->cca->req);
> > +	/* we don't really care when this settles */
> > +
> > +	return 0;
> > +}
> > +
> > +/**
> > + * crb_cmd_ready - request tpm crb device to enter ready state
> > + *
> > + * @dev:  crb device
> > + * @priv: crb private data
> > + *
> > + * Write CRB_CTRL_REQ_CMD_READY to TPM_CRB_CTRL_REQ
> > + * and poll till the device acknowledge it by clearing the bit.
> > + * The device should respond within TIMEOUT_C.
> > + *
> > + * The function does nothing for devices with ACPI-start method
> > + *
> > + * Return: 0 on success -ETIME on timeout;  */ static int
> > +__maybe_unused crb_cmd_ready(struct device *dev,
> > +					struct crb_priv *priv)
> > +{
> > +	ktime_t stop, start;
> > +
> > +	if (priv->flags & CRB_FL_ACPI_START)
> > +		return 0;
> > +
> > +	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->cca->req);
> > +
> > +	start = ktime_get();
> > +	stop = ktime_add(start, ms_to_ktime(TPM2_TIMEOUT_C));
> > +	do {
> > +		if (!(ioread32(&priv->cca->req) &
> CRB_CTRL_REQ_CMD_READY)) {
> > +			dev_dbg(dev, "cmdReady in %lld usecs\n",
> > +				ktime_to_us(ktime_sub(ktime_get(), start)));
> > +			return 0;
> > +		}
> > +		usleep_range(50, 100);
> > +	} while (ktime_before(ktime_get(), stop));
> 
> Since this is HW specific this is right thing to do and not abuse
> wait_for_tpm_stat. However, this should be documented to the commit
> message.
I will respin just this patch and not the whole series, as the fix is only in the commit message. 
Tomas

> Tested-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> 
> /Jarkko