drm/i915/dp: Read ALPM caps after DPCD init

For eDP read the ALPM DPCD caps after DPCD initalization and just before
the PSR init.

v2: Move intel_alpm_init to intel_edp_init_dpcd (Jouni)
v3: Add Fixes with commit-id (Jouni)
v4: Separated the alpm dpcd read caps from alpm_init and moved to
intel_edp_init_dpcd.
v5: Read alpm_caps always for eDP irrespective of the eDP version (Jouni)
v6: replace drm_dp_dpcd_readb with drm_dp_dpcd_read_byte (Jouni)

Fixes: 15438b3 ("drm/i915/alpm: Add compute config for lobf")
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patch.msgid.link/20260304072157.1123283-1-arun.r.murthy@intel.com
(cherry picked from commit 88442ba)
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>

Author: armurthy

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

@@ -43,12 +43,6 @@ bool intel_alpm_is_alpm_aux_less(struct intel_dp *intel_dp,
 
 void intel_alpm_init(struct intel_dp *intel_dp)
 {
-	u8 dpcd;
-
-	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_RECEIVER_ALPM_CAP, &dpcd) < 0)
-		return;
-
-	intel_dp->alpm_dpcd = dpcd;
 	mutex_init(&intel_dp->alpm.lock);
 }
 

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

@@ -4577,6 +4577,7 @@ static bool
 intel_edp_init_dpcd(struct intel_dp *intel_dp, struct intel_connector *connector)
 {
 	struct intel_display *display = to_intel_display(intel_dp);
+	int ret;
 
 	/* this function is meant to be called only once */
 	drm_WARN_ON(display->drm, intel_dp->dpcd[DP_DPCD_REV] != 0);
@@ -4616,6 +4617,12 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp, struct intel_connector *connector
 	 */
 	intel_dp_init_source_oui(intel_dp);
 
+	/* Read the ALPM DPCD caps */
+	ret = drm_dp_dpcd_read_byte(&intel_dp->aux, DP_RECEIVER_ALPM_CAP,
+				    &intel_dp->alpm_dpcd);
+	if (ret < 0)
+		return false;
+
 	/*
 	 * This has to be called after intel_dp->edp_dpcd is filled, PSR checks
 	 * for SET_POWER_CAPABLE bit in intel_dp->edp_dpcd[1]