[PATCH 04/16] drm/i915/bxt: Reset secondary power well requests left on by DMC/KVMR

[Imre Deak <imre.deak@intel.com>]

DMC forces on power well 1 by setting the corresponding request bit both
in the BIOS and the DEBUG power well request register. This is somewhat
unexpected since the firmware should really just save and restore state
but not alter it. We also depend on being able to disable power well 1,
before entering the DC9 state. To fix this make sure these request bits
are cleared whenever we want to disable the given power wells.

I've filed a bug about this, but fixing that may take a while and having
this sanity check in place makes sense even for future firmware
versions.

At the same time also check the KVMR request bits. I haven't seen this
being altered, but we don't expect any request bits in here either, so
sanitize this register as well.

Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 39 +++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index d189a00..d20fd8f 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -630,6 +630,42 @@ void skl_disable_dc6(struct drm_i915_private *dev_priv)
 	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
 }
 
+static void
+bxt_sanitize_power_well_requests(struct drm_i915_private *dev_priv,
+				 struct i915_power_well *power_well)
+{
+	enum skl_disp_power_wells power_well_id = power_well->data;
+	u32 val;
+	u32 mask;
+
+	mask = SKL_POWER_WELL_REQ(power_well_id);
+
+	val = I915_READ(HSW_PWR_WELL_KVMR);
+	if (WARN_ONCE(val & mask, "Clearing unexpected KVMR request for %s\n",
+				   power_well->name))
+		I915_WRITE(HSW_PWR_WELL_KVMR, val & ~mask);
+
+	val = I915_READ(HSW_PWR_WELL_BIOS);
+	val |= I915_READ(HSW_PWR_WELL_DEBUG);
+
+	if (!(val & mask))
+		return;
+
+	/*
+	 * DMC is known to force on the request bits for power well 1 but we
+	 * don't expect any other request bits to be set, so WARN for those.
+	 */
+	if (power_well_id == SKL_DISP_PW_1)
+		DRM_DEBUG_DRIVER("Clearing auxiliary requests for %s forced on "
+				 "by DMC\n", power_well->name);
+	else
+		WARN_ONCE(1, "Clearing unexpected auxiliary requests for %s\n",
+			  power_well->name);
+
+	I915_WRITE(HSW_PWR_WELL_BIOS, val & ~mask);
+	I915_WRITE(HSW_PWR_WELL_DEBUG, val & ~mask);
+}
+
 static void skl_set_power_well(struct drm_i915_private *dev_priv,
 			struct i915_power_well *power_well, bool enable)
 {
@@ -696,6 +732,9 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 			POSTING_READ(HSW_PWR_WELL_DRIVER);
 			DRM_DEBUG_KMS("Disabling %s\n", power_well->name);
 		}
+
+		if (IS_BROXTON(dev_priv))
+			bxt_sanitize_power_well_requests(dev_priv, power_well);
 	}
 
 	if (check_fuse_status) {
-- 
2.5.0

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