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

[Sean Paul]

On Tue, May 5, 2020 at 3:27 AM Oliver Barta <o.barta89 at gmail.com> wrote:
>
> On Mon, May 4, 2020 at 10:24 PM Sean Paul <sean at poorly.run> wrote:
> >
> > On Mon, May 4, 2020 at 1:32 PM Oliver Barta <o.barta89 at gmail.com> 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.
> > >
> > > 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)) {
> >
> > Why doesn't the wait_for catch this?
> >
> > Sean
> >
>
> Hello Sean,
>
> thank you for having a look on my patch. The wait_for can't catch this
> because it is Ri' which is outdated compared to Ri. Ri' however needs
> to be read over DDC interface which is done only once during the check
> sequence. It is not updated during the waiting time.
>

Ok, makes sense, thank you.

Reviewed-by: Sean Paul <sean at poorly.run>

> Oliver
>
> > > -               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
> > >
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> > > Intel-gfx at lists.freedesktop.org
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