drm/i915/dp: Sanitize DPCD revision check in intel_dp_get_dsc_sink_cap()

Check only the eDP or the DP specific DPCD revision depending on the
sink type. Pass the corresponding revision to the function, which allows
getting the DSC caps of a branch device (in an MST topology, which has
its own DPCD and so DPCD revision).

While at it use DP_DPCD_REV_14 instead of open coding it and for clarity
add a separate function to read out the DSC capability on eDP.

v2:
- Use DP_DPCD_REV_14 instead of open coding it. (Stan)
- Check EDP_DCPD_REV/DPCD_REV in a clearer way. (Ville)
v3:
- Fix the read-out for eDP in intel_dp_detect().

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> (v1)
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v2)
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231011171606.2540078-1-imre.deak@intel.com

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index f0f43aeabd21a6a7ca3a2fde7ed7c9e9203e205b..a010e021c48c4a0fce4879135b26b21ef9fcbd06 100644 (file)
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -3467,7 +3467,23 @@ bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp)
        return dprx & DP_VSC_SDP_EXT_FOR_COLORIMETRY_SUPPORTED;
 }
 
-static void intel_dp_get_dsc_sink_cap(struct intel_dp *intel_dp)
+static void intel_dp_read_dsc_dpcd(struct drm_dp_aux *aux,
+                                  u8 dsc_dpcd[DP_DSC_RECEIVER_CAP_SIZE])
+{
+       if (drm_dp_dpcd_read(aux, DP_DSC_SUPPORT, dsc_dpcd,
+                            DP_DSC_RECEIVER_CAP_SIZE) < 0) {
+               drm_err(aux->drm_dev,
+                       "Failed to read DPCD register 0x%x\n",
+                       DP_DSC_SUPPORT);
+               return;
+       }
+
+       drm_dbg_kms(aux->drm_dev, "DSC DPCD: %*ph\n",
+                   DP_DSC_RECEIVER_CAP_SIZE,
+                   dsc_dpcd);
+}
+
+static void intel_dp_get_dsc_sink_cap(u8 dpcd_rev, struct intel_dp *intel_dp)
 {
        struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 
@@ -3480,30 +3496,27 @@ static void intel_dp_get_dsc_sink_cap(struct intel_dp *intel_dp)
        /* Clear fec_capable to avoid using stale values */
        intel_dp->fec_capable = 0;
 
-       /* Cache the DSC DPCD if eDP or DP rev >= 1.4 */
-       if (intel_dp->dpcd[DP_DPCD_REV] >= 0x14 ||
-           intel_dp->edp_dpcd[0] >= DP_EDP_14) {
-               if (drm_dp_dpcd_read(&intel_dp->aux, DP_DSC_SUPPORT,
-                                    intel_dp->dsc_dpcd,
-                                    sizeof(intel_dp->dsc_dpcd)) < 0)
-                       drm_err(&i915->drm,
-                               "Failed to read DPCD register 0x%x\n",
-                               DP_DSC_SUPPORT);
-
-               drm_dbg_kms(&i915->drm, "DSC DPCD: %*ph\n",
-                           (int)sizeof(intel_dp->dsc_dpcd),
-                           intel_dp->dsc_dpcd);
+       if (dpcd_rev < DP_DPCD_REV_14)
+               return;
 
-               /* FEC is supported only on DP 1.4 */
-               if (!intel_dp_is_edp(intel_dp) &&
-                   drm_dp_dpcd_readb(&intel_dp->aux, DP_FEC_CAPABILITY,
-                                     &intel_dp->fec_capable) < 0)
-                       drm_err(&i915->drm,
-                               "Failed to read FEC DPCD register\n");
+       intel_dp_read_dsc_dpcd(&intel_dp->aux, intel_dp->dsc_dpcd);
 
-               drm_dbg_kms(&i915->drm, "FEC CAPABILITY: %x\n",
-                           intel_dp->fec_capable);
+       if (drm_dp_dpcd_readb(&intel_dp->aux, DP_FEC_CAPABILITY,
+                             &intel_dp->fec_capable) < 0) {
+               drm_err(&i915->drm, "Failed to read FEC DPCD register\n");
+               return;
        }
+
+       drm_dbg_kms(&i915->drm, "FEC CAPABILITY: %x\n",
+                   intel_dp->fec_capable);
+}
+
+static void intel_edp_get_dsc_sink_cap(u8 edp_dpcd_rev, struct intel_dp *intel_dp)
+{
+       if (edp_dpcd_rev < DP_EDP_14)
+               return;
+
+       intel_dp_read_dsc_dpcd(&intel_dp->aux, intel_dp->dsc_dpcd);
 }
 
 static void intel_edp_mso_mode_fixup(struct intel_connector *connector,
@@ -3674,7 +3687,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
 
        /* Read the eDP DSC DPCD registers */
        if (HAS_DSC(dev_priv))
-               intel_dp_get_dsc_sink_cap(intel_dp);
+               intel_edp_get_dsc_sink_cap(intel_dp->edp_dpcd[0],
+                                          intel_dp);
 
        /*
         * If needed, program our source OUI so we can make various Intel-specific AUX services
@@ -5342,6 +5356,23 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
                                               false);
 }
 
+static void
+intel_dp_detect_dsc_caps(struct intel_dp *intel_dp)
+{
+       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+
+       /* Read DP Sink DSC Cap DPCD regs for DP v1.4 */
+       if (!HAS_DSC(i915))
+               return;
+
+       if (intel_dp_is_edp(intel_dp))
+               intel_edp_get_dsc_sink_cap(intel_dp->edp_dpcd[0],
+                                          intel_dp);
+       else
+               intel_dp_get_dsc_sink_cap(intel_dp->dpcd[DP_DPCD_REV],
+                                         intel_dp);
+}
+
 static int
 intel_dp_detect(struct drm_connector *connector,
                struct drm_modeset_acquire_ctx *ctx,
@@ -5386,9 +5417,7 @@ intel_dp_detect(struct drm_connector *connector,
                goto out;
        }
 
-       /* Read DP Sink DSC Cap DPCD regs for DP v1.4 */
-       if (HAS_DSC(dev_priv))
-               intel_dp_get_dsc_sink_cap(intel_dp);
+       intel_dp_detect_dsc_caps(intel_dp);
 
        intel_dp_configure_mst(intel_dp);