drm/i915/tc: Abort DP AUX transfer on a disconnected TC port

On TC ports the 4ms AUX timeout combined with the 5 * 32 retry
attempts during DPCD accesses adds a 640ms delay to each access if the
sink is disconnected. This in turn slows down a modeset during which the
sink is disconnected (for instance a disabling modeset).

Prevent the above delay by aborting AUX transfers on a TC port with a
disconnected sink.

The DP 1.4a link CTS (4.2.1.5 Source Device Inactive HPD / Inactive AUX
Test") also requires not to initiate AUX transfers on disconnected DP
ports in general, however this patch doesn't change the behavior on
non-TC ports, leaving that for a follow-up.

Reported-and-tested-by: Chris Chiu <chris.chiu@canonical.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8279
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230316131724.359612-2-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 96967e21c94c2c9c813d81273fdfad9613eb653f..eb07dc5d8709906da245593939c060fb98a82c5f 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -205,8 +205,19 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
        for (i = 0; i < ARRAY_SIZE(ch_data); i++)
                ch_data[i] = intel_dp->aux_ch_data_reg(intel_dp, i);
 
-       if (is_tc_port)
+       if (is_tc_port) {
                intel_tc_port_lock(dig_port);
+               /*
+                * Abort transfers on a disconnected port as required by
+                * DP 1.4a link CTS 4.2.1.5, also avoiding the long AUX
+                * timeouts that would otherwise happen.
+                * TODO: abort the transfer on non-TC ports as well.
+                */
+               if (!intel_tc_port_connected_locked(&dig_port->base)) {
+                       ret = -ENXIO;
+                       goto out_unlock;
+               }
+       }
 
        aux_domain = intel_aux_power_domain(dig_port);
 
@@ -367,7 +378,7 @@ out:
 
        intel_pps_unlock(intel_dp, pps_wakeref);
        intel_display_power_put_async(i915, aux_domain, aux_wakeref);
-
+out_unlock:
        if (is_tc_port)
                intel_tc_port_unlock(dig_port);
 

diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
index f45328712bff1bd582dc8bf4ad2c825923c4cee9..050f998284592e20d698da41fa7d2ca32fb9c8d6 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_tc.c
+++ b/drivers/gpu/drm/i915/display/intel_tc.c
@@ -768,16 +768,23 @@ void intel_tc_port_sanitize_mode(struct intel_digital_port *dig_port)
  * connected ports are usable, and avoids exposing to the users objects they
  * can't really use.
  */
+bool intel_tc_port_connected_locked(struct intel_encoder *encoder)
+{
+       struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
+       struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
+
+       drm_WARN_ON(&i915->drm, !intel_tc_port_ref_held(dig_port));
+
+       return tc_port_live_status_mask(dig_port) & BIT(dig_port->tc_mode);
+}
+
 bool intel_tc_port_connected(struct intel_encoder *encoder)
 {
        struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
        bool is_connected;
 
        intel_tc_port_lock(dig_port);
-
-       is_connected = tc_port_live_status_mask(dig_port) &
-                      BIT(dig_port->tc_mode);
-
+       is_connected = intel_tc_port_connected_locked(encoder);
        intel_tc_port_unlock(dig_port);
 
        return is_connected;

diff --git a/drivers/gpu/drm/i915/display/intel_tc.h b/drivers/gpu/drm/i915/display/intel_tc.h
index d54082e2d5e8d75ea4a22929a525670961322d3f..93813056043a54489a6b5ecb3265906c9f792d36 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_tc.h
+++ b/drivers/gpu/drm/i915/display/intel_tc.h
@@ -17,6 +17,7 @@ bool intel_tc_port_in_dp_alt_mode(struct intel_digital_port *dig_port);
 bool intel_tc_port_in_legacy_mode(struct intel_digital_port *dig_port);
 
 bool intel_tc_port_connected(struct intel_encoder *encoder);
+bool intel_tc_port_connected_locked(struct intel_encoder *encoder);
 
 u32 intel_tc_port_get_lane_mask(struct intel_digital_port *dig_port);
 u32 intel_tc_port_get_pin_assignment_mask(struct intel_digital_port *dig_port);