[Intel-gfx] [PATCH 1/2] drm/i915: Fix scaler init during CRTC HW state readout

[Imre Deak]

The scaler allocation code depends on a non-zero default value for the
crtc scaler_id, so make sure we initialize the scaler state accordingly
even if the crtc is off. This fixes at least an initial YUV420 modeset
(added in a follow-up patchset by Shashank) when booting with the screen
off: after the initial HW readout and modeset which enables the scaler a
subsequent modeset will disable the scaler which isn't properly
allocated. This results in a funky HW state where the pipe scaler HW
registers can't be modified and the normally black screen is grey and
shifted to the right or jitters.

The problem was revealed by Shashank's YUV420 patchset and first
reported by Ville.

Cc: Shashank Sharma <shashank.sharma at intel.com>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Cc: Chandra Konduru <chandra.konduru at intel.com>
Cc: Matt Roper <matthew.d.roper at intel.com>
Cc: <stable at vger.kernel.org> # 4.11.x
Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Fixes: a1b2278e4dfc ("drm/i915: skylake panel fitting using shared scalers")
Signed-off-by: Imre Deak <imre.deak at intel.com>

---

[ Older stable versions need backporting, so that's for a follow-up ]
---
 drivers/gpu/drm/i915/intel_display.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 7774f3465fbc..8a38e64b1931 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9132,6 +9132,13 @@ static bool haswell_get_pipe_config(struct intel_crtc *crtc,
 	u64 power_domain_mask;
 	bool active;
 
+	if (INTEL_GEN(dev_priv) >= 9) {
+		intel_crtc_init_scalers(crtc, pipe_config);
+
+		pipe_config->scaler_state.scaler_id = -1;
+		pipe_config->scaler_state.scaler_users &= ~(1 << SKL_CRTC_INDEX);
+	}
+
 	power_domain = POWER_DOMAIN_PIPE(crtc->pipe);
 	if (!intel_display_power_get_if_enabled(dev_priv, power_domain))
 		return false;
@@ -9160,13 +9167,6 @@ static bool haswell_get_pipe_config(struct intel_crtc *crtc,
 	pipe_config->gamma_mode =
 		I915_READ(GAMMA_MODE(crtc->pipe)) & GAMMA_MODE_MODE_MASK;
 
-	if (INTEL_GEN(dev_priv) >= 9) {
-		intel_crtc_init_scalers(crtc, pipe_config);
-
-		pipe_config->scaler_state.scaler_id = -1;
-		pipe_config->scaler_state.scaler_users &= ~(1 << SKL_CRTC_INDEX);
-	}
-
 	power_domain = POWER_DOMAIN_PIPE_PANEL_FITTER(crtc->pipe);
 	if (intel_display_power_get_if_enabled(dev_priv, power_domain)) {
 		power_domain_mask |= BIT_ULL(power_domain);
-- 
2.13.2