[Intel-gfx] [PATCH] drm/i915/psr: Disable PSR2 selective fetch for all TGL steps

[Lyude Paul]

As we've unfortunately started to come to expect from PSR on Intel
platforms, PSR2 selective fetch is not at all ready to be enabled on
Tigerlake as it results in severe flickering issues - at least on this
ThinkPad X1 Carbon 9th generation. The easiest way I've found of
reproducing these issues is to just move the cursor around the left border
of the screen (suspicious…).

So, fix people's displays again and turn PSR2 selective fetch off for all
steppings of Tigerlake. This can be re-enabled again if someone from Intel
finds the time to fix this functionality on OEM machines.

Signed-off-by: Lyude Paul <lyude at redhat.com>
Fixes: 7f6002e58025 ("drm/i915/display: Enable PSR2 selective fetch by default")
Cc: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: José Roberto de Souza <jose.souza at intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: intel-gfx at lists.freedesktop.org
Cc: <stable at vger.kernel.org> # v5.16+
---
 drivers/gpu/drm/i915/display/intel_psr.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
index a1a663f362e7..25c16abcd9cd 100644
--- a/drivers/gpu/drm/i915/display/intel_psr.c
+++ b/drivers/gpu/drm/i915/display/intel_psr.c
@@ -737,10 +737,14 @@ static bool intel_psr2_sel_fetch_config_valid(struct intel_dp *intel_dp,
 		return false;
 	}
 
-	/* Wa_14010254185 Wa_14010103792 */
-	if (IS_TGL_DISPLAY_STEP(dev_priv, STEP_A0, STEP_C0)) {
+	/*
+	 * There's two things stopping this from being enabled on TGL:
+	 * For steps A0-C0: workarounds Wa_14010254185 Wa_14010103792 are missing
+	 * For all steps: PSR2 selective fetch causes screen flickering
+	 */
+	if (IS_TIGERLAKE(dev_priv)) {
 		drm_dbg_kms(&dev_priv->drm,
-			    "PSR2 sel fetch not enabled, missing the implementation of WAs\n");
+			    "PSR2 sel fetch not enabled, currently broken on TGL\n");
 		return false;
 	}
 
-- 
2.34.1