[Intel-gfx] [PATCH] drm/i915: HDCP: retry link integrity check on failure

[Jani Nikula]

On Tue, 05 May 2020, Ramalingam C <ramalingam.c at intel.com> wrote:
> On 2020-05-05 at 14:06:51 +0200, Oliver Barta wrote:
>> On Tue, May 5, 2020 at 9:38 AM Ramalingam C <ramalingam.c at intel.com> wrote:
>> >
>> > On 2020-05-04 at 14:35:24 +0200, Oliver Barta wrote:
>> > > From: Oliver Barta <oliver.barta at aptiv.com>
>> > >
>> > > A single Ri mismatch doesn't automatically mean that the link integrity
>> > > is broken. Update and check of Ri and Ri' are done asynchronously. In
>> > > case an update happens just between the read of Ri' and the check against
>> > > Ri there will be a mismatch even if the link integrity is fine otherwise.
>> >
>> > Thanks for working on this. Btw, did you face this sporadic link check
>> > failure or theoretically you are fixing it?
>> >
>> > IMO this change will rule out possible sporadic link check failures as
>> > mentioned in the commit msg. Though I haven't faced this issue at my
>> > testings.
>> >
>> > Reviewed-by: Ramalingam C <ramalingam.c at intel.com>
>> >
>> 
>> I found it by code inspection, the probability for this to happen is
>> very low. In order to test the patch I'm decreasing the value of
>> DRM_HDCP_CHECK_PERIOD_MS to just a few ms. Once you do that it happens
>> every few seconds.
> Ok. That make sense. Thanks for the explanation.

Finally pushed, thanks for the patch and reviews.

Ram, I was kind of expecting you to push this.

BR,
Jani.


>
> -Ram
>> 
>> Thanks,
>> Oliver
>> 
>> > >
>> > > Signed-off-by: Oliver Barta <oliver.barta at aptiv.com>
>> > > ---
>> > >  drivers/gpu/drm/i915/display/intel_hdmi.c | 19 ++++++++++++++++---
>> > >  1 file changed, 16 insertions(+), 3 deletions(-)
>> > >
>> > > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
>> > > index 010f37240710..3156fde392f2 100644
>> > > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
>> > > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
>> > > @@ -1540,7 +1540,7 @@ int intel_hdmi_hdcp_toggle_signalling(struct intel_digital_port *intel_dig_port,
>> > >  }
>> > >
>> > >  static
>> > > -bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>> > > +bool intel_hdmi_hdcp_check_link_once(struct intel_digital_port *intel_dig_port)
>> > >  {
>> > >       struct drm_i915_private *i915 = to_i915(intel_dig_port->base.base.dev);
>> > >       struct intel_connector *connector =
>> > > @@ -1563,8 +1563,7 @@ bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>> > >       if (wait_for((intel_de_read(i915, HDCP_STATUS(i915, cpu_transcoder, port)) &
>> > >                     (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC)) ==
>> > >                    (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC), 1)) {
>> > > -             drm_err(&i915->drm,
>> > > -                     "Ri' mismatch detected, link check failed (%x)\n",
>> > > +             drm_dbg_kms(&i915->drm, "Ri' mismatch detected (%x)\n",
>> > >                       intel_de_read(i915, HDCP_STATUS(i915, cpu_transcoder,
>> > >                                                       port)));
>> > >               return false;
>> > > @@ -1572,6 +1571,20 @@ bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>> > >       return true;
>> > >  }
>> > >
>> > > +static
>> > > +bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>> > > +{
>> > > +     struct drm_i915_private *i915 = to_i915(intel_dig_port->base.base.dev);
>> > > +     int retry;
>> > > +
>> > > +     for (retry = 0; retry < 3; retry++)
>> > > +             if (intel_hdmi_hdcp_check_link_once(intel_dig_port))
>> > > +                     return true;
>> > > +
>> > > +     drm_err(&i915->drm, "Link check failed\n");
>> > > +     return false;
>> > > +}
>> > > +
>> > >  struct hdcp2_hdmi_msg_timeout {
>> > >       u8 msg_id;
>> > >       u16 timeout;
>> > > --
>> > > 2.20.1
>> > >

-- 
Jani Nikula, Intel Open Source Graphics Center