RE: [PATCH v3 2/4] tmp/tpm_crb: fix Intel PTT hw bug during idle state

[Winkler, Tomas]

> 
> On Thu, Sep 15, 2016 at 09:23:29AM +0300, Jarkko Sakkinen wrote:
> > On Mon, Sep 12, 2016 at 04:04:19PM +0300, Tomas Winkler wrote:
> > > There is a HW bug in Skylake, and Broxton PCH Intel PTT device,
> > > where most of the registers in the control area except START,
> > > REQUEST, CANCEL, and LOC_CTRL lost retention when the device is in
> > > the idle state. Hence we need to bring the device to ready state
> > > before accessing the other registers. The fix brings device to ready
> > > state before trying to read command and response buffer addresses in
> order to remap the for access.
> > >
> > > Signed-off-by: Tomas Winkler <tomas.winkler@xxxxxxxxx>
> >
> > Tested-by: Jarkko Sakkinen <jarkko.sakkinn@xxxxxxxxxxxxxxx>
> > Reviewed-by: Jarkko Sakkinen <jarkko.sakkinn@xxxxxxxxxxxxxxx>
> 
> I noticed something odd or at least not described in the commit message.
> 
> > /Jarkko
> >
> > > ---
> > > V2: cmd read need to be called also before crb_init as this will run
> > > self test.
> > > V3: resend.
> > >
> > >  drivers/char/tpm/tpm_crb.c | 47
> > > ++++++++++++++++++++++++++++++++++++++--------
> > >  1 file changed, 39 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> > > index b6923a8b3ff7..e945177cf2c8 100644
> > > --- a/drivers/char/tpm/tpm_crb.c
> > > +++ b/drivers/char/tpm/tpm_crb.c
> > > @@ -318,6 +318,7 @@ static int crb_map_io(struct acpi_device *device,
> struct crb_priv *priv,
> > >  	struct list_head resources;
> > >  	struct resource io_res;
> > >  	struct device *dev = &device->dev;
> > > +	u32 pa_high, pa_low;
> > >  	u64 cmd_pa;
> > >  	u32 cmd_size;
> > >  	u64 rsp_pa;
> > > @@ -345,12 +346,27 @@ static int crb_map_io(struct acpi_device *device,
> struct crb_priv *priv,
> > >  	if (IS_ERR(priv->cca))
> > >  		return PTR_ERR(priv->cca);
> > >
> > > -	cmd_pa = ((u64) ioread32(&priv->cca->cmd_pa_high) << 32) |
> > > -		  (u64) ioread32(&priv->cca->cmd_pa_low);
> > > +	/*
> > > +	 * PTT HW bug w/a: wake up the device to access
> > > +	 * possibly not retained registers.
> > > +	 */
> > > +	ret = crb_cmd_ready(dev, priv);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	pa_high = ioread32(&priv->cca->cmd_pa_high);
> > > +	pa_low  = ioread32(&priv->cca->cmd_pa_low);
> > > +	cmd_pa = ((u64)pa_high << 32) | pa_low;
> > >  	cmd_size = ioread32(&priv->cca->cmd_size);
> > > +
> > > +	dev_dbg(dev, "cmd_hi = %X cmd_low = %X cmd_size %X\n",
> > > +		pa_high, pa_low, cmd_size);
> > > +
> > >  	priv->cmd = crb_map_res(dev, priv, &io_res, cmd_pa, cmd_size);
> > > -	if (IS_ERR(priv->cmd))
> > > -		return PTR_ERR(priv->cmd);
> > > +	if (IS_ERR(priv->cmd)) {
> > > +		ret = PTR_ERR(priv->cmd);
> > > +		goto out;
> > > +	}
> > >
> > >  	memcpy_fromio(&rsp_pa, &priv->cca->rsp_pa, 8);
> > >  	rsp_pa = le64_to_cpu(rsp_pa);
> > > @@ -358,7 +374,8 @@ static int crb_map_io(struct acpi_device
> > > *device, struct crb_priv *priv,
> > >
> > >  	if (cmd_pa != rsp_pa) {
> > >  		priv->rsp = crb_map_res(dev, priv, &io_res, rsp_pa, rsp_size);
> > > -		return PTR_ERR_OR_ZERO(priv->rsp);
> > > +		ret = PTR_ERR_OR_ZERO(priv->rsp);
> > > +		goto out;
> > >  	}
> > >
> > >  	/* According to the PTP specification, overlapping command and
> > > response @@ -366,12 +383,18 @@ static int crb_map_io(struct
> acpi_device *device, struct crb_priv *priv,
> > >  	 */
> > >  	if (cmd_size != rsp_size) {
> > >  		dev_err(dev, FW_BUG "overlapping command and response
> buffer sizes are not identical");
> > > -		return -EINVAL;
> > > +		ret = -EINVAL;
> > > +		goto out;
> > >  	}
> > > +
> > >  	priv->cmd_size = cmd_size;
> > >
> > >  	priv->rsp = priv->cmd;
> > > -	return 0;
> > > +
> > > +out:
> > > +	crb_go_idle(dev, priv);
> > > +
> > > +	return ret;
> > >  }
> > >
> > >  static int crb_acpi_add(struct acpi_device *device) @@ -415,7
> > > +438,15 @@ static int crb_acpi_add(struct acpi_device *device)
> > >  	if (rc)
> > >  		return rc;
> > >
> > > -	return crb_init(device, priv);
> > > +	rc  = crb_cmd_ready(dev, priv);
> > > +	if (rc)
> > > +		return rc;
> 
> You do this already in crb_map_io() that is called before crb_init().
> What is the purpose of this extra crb_cmd_ready()? Looks unrelated at least to
> the described workaround.

Runtime pm can be not compiled into kernel, in that case you would have nonfunctional devices, hence we start the  init flow in explicitly enabled state. 
Thanks
Tomas