[Intel-gfx] [PATCH 04/18] drm/i915/gen9: block disable call for pw1 if dmc firmware is present.

[Animesh Manna]

Grabbing a runtime pm reference with intel_runtime_pm_get will only
prevent device D3. But dmc firmware is required even earlier (namely
for the skl power well 1). DMC is responsible to save the status of
power well 1 and shut off the power well when panel is self refresh
mode of display is completely off.

Another interesting criteria to work dmc as expected is pw1 to be
enabled by driver and dmc will shut it off in its execution
sequence. If already disabled by driver dmc will get confuse and
behave differently than expected found during pc10 entry issue
for skl.

So berfore we disable power-well 1, added check if dmc firmware is
present and driver will not disable power well 1, but for any reason
if firmware is not present of failed to load we can shut off the
power well 1 which will save some power.

As skl is currently fully dependent on dmc to go in lowest possible
power state (dc6) but the same is not applicable for bxt. Display
engine can enter into dc9 without dmc, hence unblocking disable call.

Cc: Daniel Vetter <daniel.vetter at intel.com>
Cc: Damien Lespiau <damien.lespiau at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Cc: Sunil Kamath <sunil.kamath at intel.com>
Signed-off-by: Animesh Manna <animesh.manna at intel.com>
Signed-off-by: Vathsala Nagaraju <vathsala.nagaraju at intel.com>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 6393b76..e6156d5 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -1141,8 +1141,10 @@ void intel_display_power_put(struct drm_i915_private *dev_priv,
 
 	for_each_power_well_rev(i, power_well, BIT(domain), power_domains) {
 		WARN_ON(!power_well->count);
-
-		if (!--power_well->count && i915.disable_power_well) {
+		if (IS_SKYLAKE(dev_priv) && (power_well->data == SKL_DISP_PW_1) &&
+			(intel_csr_load_status_get(dev_priv) == FW_LOADED))
+			DRM_DEBUG_KMS("dmc will disable pw1");
+		else if (!--power_well->count && i915.disable_power_well) {
 			DRM_DEBUG_KMS("disabling %s\n", power_well->name);
 			power_well->hw_enabled = false;
 			power_well->ops->disable(dev_priv, power_well);
-- 
2.0.2