[PATCH 1/3] i915/display/intel_dp: Read PCON DSC ENC caps only for DPCD rev >= 1.4

[Ankit Nautiyal]

DP-HDMI2.1 PCON has DSC encoder aps defined in registers 0x92-0x9C.
Do not read the registers if DPCD rev < 1.4.

Fixes: https://gitlab.freedesktop.org/drm/intel/-/issues/2868
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 8c12d5375607..2b83f0f433a2 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -2489,9 +2489,11 @@ static void intel_dp_get_pcon_dsc_cap(struct intel_dp *intel_dp)
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 
 	/* Clear the cached register set to avoid using stale values */
-
 	memset(intel_dp->pcon_dsc_dpcd, 0, sizeof(intel_dp->pcon_dsc_dpcd));
 
+	if (intel_dp->dpcd[DP_DPCD_REV] < 0x14)
+		return;
+
 	if (drm_dp_dpcd_read(&intel_dp->aux, DP_PCON_DSC_ENCODER,
 			     intel_dp->pcon_dsc_dpcd,
 			     sizeof(intel_dp->pcon_dsc_dpcd)) < 0)
-- 
2.29.2