[PATCH v2] drm/i915/hdcp: Add additional R0' wait

[Ramalingam C]

On 2020-05-20 at 15:50:15 -0400, Sean Paul wrote:
> On Wed, May 20, 2020 at 9:08 AM Sean Paul <sean at poorly.run> wrote:
> >
> > From: Sean Paul <seanpaul at chromium.org>
> >
> > We're seeing some R0' mismatches in the field, particularly with
> > repeaters. I'm guessing the (already lenient) 300ms wait time isn't
> > enough for some setups. So add an additional wait when R0' is
> > mismatched.
> >
> 
> I think my guess was wrong and now suspect this issue is fixed with
> "drm/i915/hdcp: Avoid duplicate HDCP enables".
> 
> While this patch probably still has some value in cases where R0' is
> slow to update, I don't have any concrete examples where it helps.
Sean, completely agree it will help to authenticate the slower hdcp sink,
as this is not breaking the spec too. But could we please introduce extra
delays when we encounter such needs?

As you mentioned, We already have a 3 * 100 mSec,
where spec says HDCP sink should keep the R0' ready after the 100mSec
from aksv write.

-Ram
> 
> Sean
> 
> 
> > Signed-off-by: Sean Paul <seanpaul at chromium.org>
> >
> > Changes in v2:
> > - Actually add the delay in R0` wait (Ram)
> > ---
> >
> > Apologies, v1 was generated from a forward port from the CrOS kernel and
> > patch got confused and put the diff in V' wait instead of R0' wait.
> >
> > Pay closer attention, Sean.
> >
> >  drivers/gpu/drm/i915/display/intel_hdcp.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > index 2cbc4619b4ce..3c2d8c0a6da6 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > @@ -743,6 +743,9 @@ static int intel_hdcp_auth(struct intel_connector *connector)
> >                 if (!wait_for(intel_de_read(dev_priv, HDCP_STATUS(dev_priv, cpu_transcoder, port)) &
> >                               (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC), 1))
> >                         break;
> > +
> > +               /* Maybe the sink is lazy, give it some more time */
> > +               usleep_range(10000, 50000);
> >         }
> >
> >         if (i == tries) {
> > --
> > Sean Paul, Software Engineer, Google / Chromium OS
> >