Merge tag 'drm-intel-fixes-2021-05-27' of...

Merge tag 'drm-intel-fixes-2021-05-27' of ssh://git.freedesktop.org/git/drm/drm-intel into drm-fixes

drm/i915 fixes for v5.13-rc4:
- Re-enable LTTPR non-transparent LT mode for DPCD_REV<1.4
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/875yz4bnmj.fsf@intel.com

drivers/gpu/drm/i915/display/intel_dp_link_training.c

@@ -128,49 +128,13 @@ intel_dp_set_lttpr_transparent_mode(struct intel_dp *intel_dp, bool enable)
 	return drm_dp_dpcd_write(&intel_dp->aux, DP_PHY_REPEATER_MODE, &val, 1) == 1;
 }
 
-/**
- * intel_dp_init_lttpr_and_dprx_caps - detect LTTPR and DPRX caps, init the LTTPR link training mode
- * @intel_dp: Intel DP struct
- *
- * Read the LTTPR common and DPRX capabilities and switch to non-transparent
- * link training mode if any is detected and read the PHY capabilities for all
- * detected LTTPRs. In case of an LTTPR detection error or if the number of
- * LTTPRs is more than is supported (8), fall back to the no-LTTPR,
- * transparent mode link training mode.
- *
- * Returns:
- *   >0  if LTTPRs were detected and the non-transparent LT mode was set. The
- *       DPRX capabilities are read out.
- *    0  if no LTTPRs or more than 8 LTTPRs were detected or in case of a
- *       detection failure and the transparent LT mode was set. The DPRX
- *       capabilities are read out.
- *   <0  Reading out the DPRX capabilities failed.
- */
-int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp)
+static int intel_dp_init_lttpr(struct intel_dp *intel_dp)
 {
 	int lttpr_count;
-	bool ret;
 	int i;
 
-	ret = intel_dp_read_lttpr_common_caps(intel_dp);
-
-	/* The DPTX shall read the DPRX caps after LTTPR detection. */
-	if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd)) {
-		intel_dp_reset_lttpr_common_caps(intel_dp);
-		return -EIO;
-	}
-
-	if (!ret)
-		return 0;
-
-	/*
-	 * The 0xF0000-0xF02FF range is only valid if the DPCD revision is
-	 * at least 1.4.
-	 */
-	if (intel_dp->dpcd[DP_DPCD_REV] < 0x14) {
-		intel_dp_reset_lttpr_common_caps(intel_dp);
+	if (!intel_dp_read_lttpr_common_caps(intel_dp))
 		return 0;
-	}
 
 	lttpr_count = drm_dp_lttpr_count(intel_dp->lttpr_common_caps);
 	/*
@@ -211,6 +175,37 @@ int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp)
 
 	return lttpr_count;
 }
+
+/**
+ * intel_dp_init_lttpr_and_dprx_caps - detect LTTPR and DPRX caps, init the LTTPR link training mode
+ * @intel_dp: Intel DP struct
+ *
+ * Read the LTTPR common and DPRX capabilities and switch to non-transparent
+ * link training mode if any is detected and read the PHY capabilities for all
+ * detected LTTPRs. In case of an LTTPR detection error or if the number of
+ * LTTPRs is more than is supported (8), fall back to the no-LTTPR,
+ * transparent mode link training mode.
+ *
+ * Returns:
+ *   >0  if LTTPRs were detected and the non-transparent LT mode was set. The
+ *       DPRX capabilities are read out.
+ *    0  if no LTTPRs or more than 8 LTTPRs were detected or in case of a
+ *       detection failure and the transparent LT mode was set. The DPRX
+ *       capabilities are read out.
+ *   <0  Reading out the DPRX capabilities failed.
+ */
+int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp)
+{
+	int lttpr_count = intel_dp_init_lttpr(intel_dp);
+
+	/* The DPTX shall read the DPRX caps after LTTPR detection. */
+	if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd)) {
+		intel_dp_reset_lttpr_common_caps(intel_dp);
+		return -EIO;
+	}
+
+	return lttpr_count;
+}
 EXPORT_SYMBOL(intel_dp_init_lttpr_and_dprx_caps);
 
 static u8 dp_voltage_max(u8 preemph)