drm/i915/hdcp: Avoid duplicate HDCP enables
diff mbox series

Message ID 20200520194744.48936-1-sean@poorly.run
State New
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  • drm/i915/hdcp: Avoid duplicate HDCP enables
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Commit Message

Sean Paul May 20, 2020, 7:47 p.m. UTC
From: Sean Paul <seanpaul@chromium.org>

If userspace sets the CP property to DESIRED while it's already ENABLED,
the driver will try to re-enable HDCP. On some displays, this will
result in R0' mismatches. I'm guessing this is because the display is
still sending back Ri instead of re-authenticating.

At any rate, we can fix this inefficiency easily enough by just nooping
the DESIRED property set if HDCP is already ENABLED.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
---

I suspect this is the actual root cause I was chasing with
"drm/i915/hdcp: Add additional R0' wait". I was able to reproduce the
R0` messages by marking HDCP desired while it was already enabled. This
_should_ work, but it seems like some displays handle it more graciously
than others.


 drivers/gpu/drm/i915/display/intel_hdcp.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

Comments

Ramalingam C May 21, 2020, 4:57 a.m. UTC | #1
On 2020-05-20 at 15:47:44 -0400, Sean Paul wrote:
> From: Sean Paul <seanpaul@chromium.org>
> 
> If userspace sets the CP property to DESIRED while it's already ENABLED,
> the driver will try to re-enable HDCP. On some displays, this will
> result in R0' mismatches. I'm guessing this is because the display is
> still sending back Ri instead of re-authenticating.
> 
> At any rate, we can fix this inefficiency easily enough by just nooping
> the DESIRED property set if HDCP is already ENABLED.
Sean,

This will skip the hdcp enable.

But at present too we will be getting below WARN_ON from intel_hdcp_enable,
to indicate userspace is going wrong with request.
        drm_WARN_ON(&dev_priv->drm,
                    hdcp->value == DRM_MODE_CONTENT_PROTECTION_ENABLED);

And if we need to filter this out, could we validate the incoming hdcp request at
drm_atomic_connector_set_property() itself? No point in going into the
atomic commit without a valid request. something like

diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index a1e5e262bae2..d98b2eeae78d 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -746,6 +746,12 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
                        DRM_DEBUG_KMS("only drivers can set CP Enabled\n");
                        return -EINVAL;
                }
+               if (config->content_protection_property ==
+                   DRM_MODE_CONTENT_PROTECTION_ENABLED &&
+                   val == DRM_MODE_CONTENT_PROTECTION_DESIRED) {
+                       DRM_DEBUG_KMS("Redundant req for content protection\n");
+                       return -EINVAL;
+               }
                state->content_protection = val;
        } else if (property == config->hdcp_content_type_property) {
                state->hdcp_content_type = val;

-Ram

> 
> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> ---
> 
> I suspect this is the actual root cause I was chasing with
> "drm/i915/hdcp: Add additional R0' wait". I was able to reproduce the
> R0` messages by marking HDCP desired while it was already enabled. This
> _should_ work, but it seems like some displays handle it more graciously
> than others.
> 
> 
>  drivers/gpu/drm/i915/display/intel_hdcp.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index 2cbc4619b4ce..f770fe0c5595 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> @@ -2156,12 +2156,16 @@ void intel_hdcp_atomic_check(struct drm_connector *connector,
>  	}
>  
>  	/*
> -	 * Nothing to do if the state didn't change, or HDCP was activated since
> -	 * the last commit. And also no change in hdcp content type.
> +	 * Nothing to do if content type is unchanged and one of:
> +	 *  - state didn't change
> +	 *  - HDCP was activated since the last commit
> +	 *  - attempting to set to desired while already enabled
>  	 */
>  	if (old_cp == new_cp ||
>  	    (old_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
> -	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED)) {
> +	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
> +	    (old_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> +	     new_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
>  		if (old_state->hdcp_content_type ==
>  				new_state->hdcp_content_type)
>  			return;
> -- 
> Sean Paul, Software Engineer, Google / Chromium OS
>
Anshuman Gupta May 21, 2020, 9:27 a.m. UTC | #2
On 2020-05-21 at 10:27:21 +0530, Ramalingam C wrote:
> On 2020-05-20 at 15:47:44 -0400, Sean Paul wrote:
> > From: Sean Paul <seanpaul@chromium.org>
> > 
> > If userspace sets the CP property to DESIRED while it's already ENABLED,
> > the driver will try to re-enable HDCP. On some displays, this will
> > result in R0' mismatches. I'm guessing this is because the display is
> > still sending back Ri instead of re-authenticating.
> > 
> > At any rate, we can fix this inefficiency easily enough by just nooping
> > the DESIRED property set if HDCP is already ENABLED.
AFAIU may below patch also solves above issue implicitly.
https://patchwork.freedesktop.org/patch/365758/?series=72251&rev=4
Besides that +1 for below Ram comment, it would be better if such type of duplicate
enable request should filter by drm_atomic_connector_set_property().
Thanks,
Anshuman Gupta.

> Sean,
> 
> This will skip the hdcp enable.
> 
> But at present too we will be getting below WARN_ON from intel_hdcp_enable,
> to indicate userspace is going wrong with request.
>         drm_WARN_ON(&dev_priv->drm,
>                     hdcp->value == DRM_MODE_CONTENT_PROTECTION_ENABLED);
> 
> And if we need to filter this out, could we validate the incoming hdcp request at
> drm_atomic_connector_set_property() itself? No point in going into the
> atomic commit without a valid request. something like
> 
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index a1e5e262bae2..d98b2eeae78d 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -746,6 +746,12 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
>                         DRM_DEBUG_KMS("only drivers can set CP Enabled\n");
>                         return -EINVAL;
>                 }
> +               if (config->content_protection_property ==
> +                   DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> +                   val == DRM_MODE_CONTENT_PROTECTION_DESIRED) {
> +                       DRM_DEBUG_KMS("Redundant req for content protection\n");
> +                       return -EINVAL;
> +               }
>                 state->content_protection = val;
>         } else if (property == config->hdcp_content_type_property) {
>                 state->hdcp_content_type = val;
> 
> -Ram
> 
> > 
> > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > ---
> > 
> > I suspect this is the actual root cause I was chasing with
> > "drm/i915/hdcp: Add additional R0' wait". I was able to reproduce the
> > R0` messages by marking HDCP desired while it was already enabled. This
> > _should_ work, but it seems like some displays handle it more graciously
> > than others.
> > 
> > 
> >  drivers/gpu/drm/i915/display/intel_hdcp.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > index 2cbc4619b4ce..f770fe0c5595 100644
> > --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > @@ -2156,12 +2156,16 @@ void intel_hdcp_atomic_check(struct drm_connector *connector,
> >  	}
> >  
> >  	/*
> > -	 * Nothing to do if the state didn't change, or HDCP was activated since
> > -	 * the last commit. And also no change in hdcp content type.
> > +	 * Nothing to do if content type is unchanged and one of:
> > +	 *  - state didn't change
> > +	 *  - HDCP was activated since the last commit
> > +	 *  - attempting to set to desired while already enabled
> >  	 */
> >  	if (old_cp == new_cp ||
> >  	    (old_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
> > -	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED)) {
> > +	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
> > +	    (old_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> > +	     new_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
> >  		if (old_state->hdcp_content_type ==
> >  				new_state->hdcp_content_type)
> >  			return;
> > -- 
> > Sean Paul, Software Engineer, Google / Chromium OS
> >
Sean Paul May 21, 2020, 1:38 p.m. UTC | #3
On Thu, May 21, 2020 at 5:36 AM Anshuman Gupta <anshuman.gupta@intel.com> wrote:
>
> On 2020-05-21 at 10:27:21 +0530, Ramalingam C wrote:
> > On 2020-05-20 at 15:47:44 -0400, Sean Paul wrote:
> > > From: Sean Paul <seanpaul@chromium.org>
> > >
> > > If userspace sets the CP property to DESIRED while it's already ENABLED,
> > > the driver will try to re-enable HDCP. On some displays, this will
> > > result in R0' mismatches. I'm guessing this is because the display is
> > > still sending back Ri instead of re-authenticating.
> > >
> > > At any rate, we can fix this inefficiency easily enough by just nooping
> > > the DESIRED property set if HDCP is already ENABLED.
> AFAIU may below patch also solves above issue implicitly.
> https://patchwork.freedesktop.org/patch/365758/?series=72251&rev=4
> Besides that +1 for below Ram comment, it would be better if such type of duplicate
> enable request should filter by drm_atomic_connector_set_property().

Thanks Anshuman, I didn't see that patch. Indeed that seems like it
accomplishes the same thing.

Let's drop this.

Sean

> Thanks,
> Anshuman Gupta.
>
> > Sean,
> >
> > This will skip the hdcp enable.
> >
> > But at present too we will be getting below WARN_ON from intel_hdcp_enable,
> > to indicate userspace is going wrong with request.
> >         drm_WARN_ON(&dev_priv->drm,
> >                     hdcp->value == DRM_MODE_CONTENT_PROTECTION_ENABLED);
> >
> > And if we need to filter this out, could we validate the incoming hdcp request at
> > drm_atomic_connector_set_property() itself? No point in going into the
> > atomic commit without a valid request. something like
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> > index a1e5e262bae2..d98b2eeae78d 100644
> > --- a/drivers/gpu/drm/drm_atomic_uapi.c
> > +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> > @@ -746,6 +746,12 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
> >                         DRM_DEBUG_KMS("only drivers can set CP Enabled\n");
> >                         return -EINVAL;
> >                 }
> > +               if (config->content_protection_property ==
> > +                   DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> > +                   val == DRM_MODE_CONTENT_PROTECTION_DESIRED) {
> > +                       DRM_DEBUG_KMS("Redundant req for content protection\n");
> > +                       return -EINVAL;
> > +               }
> >                 state->content_protection = val;
> >         } else if (property == config->hdcp_content_type_property) {
> >                 state->hdcp_content_type = val;
> >
> > -Ram
> >
> > >
> > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > ---
> > >
> > > I suspect this is the actual root cause I was chasing with
> > > "drm/i915/hdcp: Add additional R0' wait". I was able to reproduce the
> > > R0` messages by marking HDCP desired while it was already enabled. This
> > > _should_ work, but it seems like some displays handle it more graciously
> > > than others.
> > >
> > >
> > >  drivers/gpu/drm/i915/display/intel_hdcp.c | 10 +++++++---
> > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > > index 2cbc4619b4ce..f770fe0c5595 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> > > @@ -2156,12 +2156,16 @@ void intel_hdcp_atomic_check(struct drm_connector *connector,
> > >     }
> > >
> > >     /*
> > > -    * Nothing to do if the state didn't change, or HDCP was activated since
> > > -    * the last commit. And also no change in hdcp content type.
> > > +    * Nothing to do if content type is unchanged and one of:
> > > +    *  - state didn't change
> > > +    *  - HDCP was activated since the last commit
> > > +    *  - attempting to set to desired while already enabled
> > >      */
> > >     if (old_cp == new_cp ||
> > >         (old_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
> > > -        new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED)) {
> > > +        new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
> > > +       (old_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
> > > +        new_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
> > >             if (old_state->hdcp_content_type ==
> > >                             new_state->hdcp_content_type)
> > >                     return;
> > > --
> > > Sean Paul, Software Engineer, Google / Chromium OS
> > >
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
index 2cbc4619b4ce..f770fe0c5595 100644
--- a/drivers/gpu/drm/i915/display/intel_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
@@ -2156,12 +2156,16 @@  void intel_hdcp_atomic_check(struct drm_connector *connector,
 	}
 
 	/*
-	 * Nothing to do if the state didn't change, or HDCP was activated since
-	 * the last commit. And also no change in hdcp content type.
+	 * Nothing to do if content type is unchanged and one of:
+	 *  - state didn't change
+	 *  - HDCP was activated since the last commit
+	 *  - attempting to set to desired while already enabled
 	 */
 	if (old_cp == new_cp ||
 	    (old_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED &&
-	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED)) {
+	     new_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED) ||
+	    (old_cp == DRM_MODE_CONTENT_PROTECTION_ENABLED &&
+	     new_cp == DRM_MODE_CONTENT_PROTECTION_DESIRED)) {
 		if (old_state->hdcp_content_type ==
 				new_state->hdcp_content_type)
 			return;