[PATCH 10/38][SRU][G/H] drm/i915: HDCP: retry link integrity check on failure

[You-Sheng Yang]

From: Oliver Barta <oliver.barta at aptiv.com>

BugLink: https://bugs.launchpad.net/bugs/1903969

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>
Reviewed-by: Sean Paul <sean at poorly.run>
Reviewed-by: Ramalingam C <ramalingam.c at intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200504123524.7731-1-oliver.barta@aptiv.com
(cherry picked from commit b08239b2f47190981309c29149e31f111f699aab)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.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 093751481271..e98d44772c7b 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -1545,7 +1545,7 @@ 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 =
@@ -1568,8 +1568,7 @@ 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;
@@ -1577,6 +1576,20 @@ 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;
-- 
2.29.2