[Intel-gfx] [PATCH v3] drm/i915/hdcp: Update CP as per the kernel internal state

[Jani Nikula]

On Mon, 20 Jan 2020, Ramalingam C <ramalingam.c at intel.com> wrote:
> On 2020-01-20 at 12:29:36 +0200, Jani Nikula wrote:
>> On Mon, 20 Jan 2020, Ramalingam C <ramalingam.c at intel.com> wrote:
>> > On 2020-01-20 at 11:19:54 +0530, Anshuman Gupta wrote:
>> >> Content Protection property should be updated as per the kernel
>> >> internal state. Let's say if Content protection is disabled
>> >> by userspace, CP property should be set to UNDESIRED so that
>> >> reauthentication will not happen until userspace request it again,
>> >> but when kernel disables the HDCP due to any DDI disabling sequences
>> >> like modeset/DPMS operation, kernel should set the property to
>> >> DESIRED, so that when opportunity arises, kernel will start the
>> >> HDCP authentication on its own.
>> >> 
>> >> Somewhere in the line, state machine to set content protection to
>> >> DESIRED from kernel was broken and IGT coverage was missing for it.
>> >> This patch fixes it.
>> >> IGT patch to catch further regression on this features is being
>> >> worked upon.
>> >> 
>> >> v2:
>> >>  - Incorporated the necessary locking. (Ram)
>> >>  - Set content protection property to CP_DESIRED only when
>> >>    user has not asked explicitly to set CP_UNDESIRED.
>> >> 
>> >> v3:
>> >>  - Reset the is_hdcp_undesired flag to false. (Ram)
>> >>  - Rephrasing commit log and small comment for is_hdcp_desired
>> >>    flag. (Ram)
>> >> 
>> >> CC: Ramalingam C <ramalingam.c at intel.com>
>> >> Reviewed-by: Ramalingam C <ramalingam.c at intel.com>
>> >> Signed-off-by: Anshuman Gupta <anshuman.gupta at intel.com>
>> >> ---
>> >>  drivers/gpu/drm/i915/display/intel_display_types.h |  6 ++++++
>> >>  drivers/gpu/drm/i915/display/intel_hdcp.c          | 13 ++++++++++++-
>> >>  2 files changed, 18 insertions(+), 1 deletion(-)
>> >> 
>> >> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
>> >> index 630a94892b7b..401a9a7689fb 100644
>> >> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> >> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> >> @@ -345,6 +345,12 @@ struct intel_hdcp {
>> >>  	struct delayed_work check_work;
>> >>  	struct work_struct prop_work;
>> >>  
>> >> +	/*
>> >> +	 * Flag to differentiate that HDCP is being disabled originated from
>> >> +	 * userspace or triggered from kernel DDI disable sequence.
>> >> +	 */
>> >> +	bool is_hdcp_undesired;
>> > Jani and Daniel,
>> >
>> > This flag is added as we need to know the origin of the HDCP disable
>> > (userspace or kernel modeset/DPMS off) at DDI disable sequence. We
>> > couldn't do that as new_conn state is not available there to retrieve
>> > the corresponding content protection state.
>> >
>> > Hence we do that at atomic check itself and pass the info through this flag,
>> > which will be referred at hdcp_disable.
>> >
>> > If you think we could do it better please suggest the preferred
>> > alternate method. Else I request your ack for merging this.
>> 
>> I don't know hdcp code all that well, but it seems to me at the root of
>> the problem is the duplication of the content protection state
>> (drm_connector_state->content_protection) into the connector
>> (intel_hdcp->value), and them going out of sync.
>> 
>> If you relied on the connector state alone, you wouldn't have to worry
>> about changing the intel_hdcp->value member at disable or anywhere;
>> disable looks at old state and disables based on that. No history/future
>> information needed. Isn't that roughly what everything else does, why is
>> hdcp special?
> As per uAPI designed for Chrome(first user of HDCP), after the userspace
> request for HDCP by setting DESIRED to "content protection" only userspace can DISABLED it.
>
> Incase when HDCP is ENABLED and kernel ended up in disabled the DDI (hot
> unplug or DPMS ops), it supposed to disable HDCP encryption and leave the
> "Content protection" at DESIRED. So that when the DDI is re enabled,
> HDCP authentication will be attempted automatically, as userspace is
> still interested in HDCP encryption.
>
> So to set the state of "content protection" as  ENABLED->DESIRED, we
> need to know the HDCP disable in DDI disable is not because of userspace request
> (derived based on new connector state existance and its content protection state).
>
> Hence we need this change.

Okay, why do you need to track desired/undesired in intel_hdcp then?
Just track enabled/disabled, and do everything else based on connector
state?

BR,
Jani.


>
> -Ram
>> 
>> BR,
>> Jani.
>> 
>> 
>> >
>> > Thanks,
>> > -Ram
>> >> +
>> >>  	/* HDCP1.4 Encryption status */
>> >>  	bool hdcp_encrypted;
>> >>  
>> >> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
>> >> index 0fdbd39f6641..7f631ebd8395 100644
>> >> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
>> >> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
>> >> @@ -2002,11 +2002,18 @@ int intel_hdcp_disable(struct intel_connector *connector)
>> >>  	mutex_lock(&hdcp->mutex);
>> >>  
>> >>  	if (hdcp->value != DRM_MODE_CONTENT_PROTECTION_UNDESIRED) {
>> >> -		hdcp->value = DRM_MODE_CONTENT_PROTECTION_UNDESIRED;
>> >>  		if (hdcp->hdcp2_encrypted)
>> >>  			ret = _intel_hdcp2_disable(connector);
>> >>  		else if (hdcp->hdcp_encrypted)
>> >>  			ret = _intel_hdcp_disable(connector);
>> >> +
>> >> +		if (hdcp->is_hdcp_undesired) {
>> >> +			hdcp->value = DRM_MODE_CONTENT_PROTECTION_UNDESIRED;
>> >> +			hdcp->is_hdcp_undesired = false;
>> >> +		} else {
>> >> +			hdcp->value = DRM_MODE_CONTENT_PROTECTION_DESIRED;
>> >> +			schedule_work(&hdcp->prop_work);
>> >> +		}
>> >>  	}
>> >>  
>> >>  	mutex_unlock(&hdcp->mutex);
>> >> @@ -2044,6 +2051,7 @@ void intel_hdcp_atomic_check(struct drm_connector *connector,
>> >>  {
>> >>  	u64 old_cp = old_state->content_protection;
>> >>  	u64 new_cp = new_state->content_protection;
>> >> +	struct intel_connector *intel_conn = to_intel_connector(connector);
>> >>  	struct drm_crtc_state *crtc_state;
>> >>  
>> >>  	if (!new_state->crtc) {
>> >> @@ -2069,6 +2077,9 @@ void intel_hdcp_atomic_check(struct drm_connector *connector,
>> >>  			return;
>> >>  	}
>> >>  
>> >> +	if (new_cp == DRM_MODE_CONTENT_PROTECTION_UNDESIRED)
>> >> +		intel_conn->hdcp.is_hdcp_undesired  =  true;
>> >> +
>> >>  	crtc_state = drm_atomic_get_new_crtc_state(new_state->state,
>> >>  						   new_state->crtc);
>> >>  	crtc_state->mode_changed = true;
>> >> -- 
>> >> 2.24.0
>> >> 
>> 
>> -- 
>> Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center