[PATCH v2] drm/i915/hdcp: Disable the QSES check for HDCP 1.4 over MST

[Sean Paul]

From: Sean Paul <seanpaul at chromium.org>

The HDCP 1.4 spec does not require the QUERY_STREAM_ENCRYPTION_STATUS
check, it was always a nice-to-have. After deploying this across various
devices, we've determined that some MST bridge chips do not properly
support this call for HDCP 1.4 (namely Synaptics and Realtek).

I had considered creating a quirk for this, but I think it's more
prudent to just disable the check entirely since I don't have an idea
how widespread support is.

Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Reviewed-by: Anshuman Gupta <anshuman.gupta at intel.com>
Signed-off-by: Sean Paul <seanpaul at chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210106223909.34476-1-sean@poorly.run #v1

Changes in v2:
-Rebased on -tip
---
 drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
index f372e25edab4..4dba5bb15af5 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
@@ -722,16 +722,6 @@ static bool intel_dp_mst_get_qses_status(struct intel_digital_port *dig_port,
 	return reply.auth_completed && reply.encryption_enabled;
 }
 
-static
-bool intel_dp_mst_hdcp_check_link(struct intel_digital_port *dig_port,
-				  struct intel_connector *connector)
-{
-	if (!intel_dp_hdcp_check_link(dig_port, connector))
-		return false;
-
-	return intel_dp_mst_get_qses_status(dig_port, connector);
-}
-
 static int
 intel_dp_mst_hdcp2_stream_encryption(struct intel_connector *connector,
 				     bool enable)
@@ -805,7 +795,7 @@ static const struct intel_hdcp_shim intel_dp_mst_hdcp_shim = {
 	.read_v_prime_part = intel_dp_hdcp_read_v_prime_part,
 	.toggle_signalling = intel_dp_hdcp_toggle_signalling,
 	.stream_encryption = intel_dp_mst_hdcp_stream_encryption,
-	.check_link = intel_dp_mst_hdcp_check_link,
+	.check_link = intel_dp_hdcp_check_link,
 	.hdcp_capable = intel_dp_hdcp_capable,
 	.write_2_2_msg = intel_dp_hdcp2_write_msg,
 	.read_2_2_msg = intel_dp_hdcp2_read_msg,
-- 
Sean Paul, Software Engineer, Google / Chromium OS