[Intel-gfx] [PATCH 09/18] drm/i915/gen9+: Remove redundant state check during power well toggling

[Imre Deak]

Atm we enable/disable a power well only if it wasn't already
enabled/disabled respectively. The only reason for this I can think of
is to save the extra MMIO writes. Since the HW state matches the power
well's usage counter most of the time the overhead due to these MMIOs is
insignificant. Let's simplify the code by making the writes
unconditional.

Signed-off-by: Imre Deak <imre.deak at intel.com>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 85c592d..28d2ea9 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -806,7 +806,7 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 {
 	uint32_t tmp, fuse_status;
 	uint32_t req_mask, state_mask;
-	bool is_enabled, enable_requested, check_fuse_status = false;
+	bool check_fuse_status = false;
 
 	tmp = I915_READ(HSW_PWR_WELL_DRIVER);
 	fuse_status = I915_READ(SKL_FUSE_STATUS);
@@ -844,29 +844,22 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 	}
 
 	req_mask = SKL_POWER_WELL_REQ(power_well->id);
-	enable_requested = tmp & req_mask;
 	state_mask = SKL_POWER_WELL_STATE(power_well->id);
-	is_enabled = tmp & state_mask;
 
-	if (!enable && enable_requested)
+	if (!enable)
 		skl_power_well_pre_disable(dev_priv, power_well);
 
 	if (enable) {
-		if (!enable_requested)
-			I915_WRITE(HSW_PWR_WELL_DRIVER, tmp | req_mask);
+		I915_WRITE(HSW_PWR_WELL_DRIVER, tmp | req_mask);
 
-		if (!is_enabled) {
-			DRM_DEBUG_KMS("Enabling %s\n", power_well->name);
-			check_fuse_status = true;
-		}
+		DRM_DEBUG_KMS("Enabling %s\n", power_well->name);
+		check_fuse_status = true;
 
 		gen9_wait_for_power_well_enable(dev_priv, power_well);
 	} else {
-		if (enable_requested) {
-			I915_WRITE(HSW_PWR_WELL_DRIVER,	tmp & ~req_mask);
-			POSTING_READ(HSW_PWR_WELL_DRIVER);
-			DRM_DEBUG_KMS("Disabling %s\n", power_well->name);
-		}
+		I915_WRITE(HSW_PWR_WELL_DRIVER,	tmp & ~req_mask);
+		POSTING_READ(HSW_PWR_WELL_DRIVER);
+		DRM_DEBUG_KMS("Disabling %s\n", power_well->name);
 
 		gen9_wait_for_power_well_disable(dev_priv, power_well);
 	}
@@ -889,7 +882,7 @@ static void skl_set_power_well(struct drm_i915_private *dev_priv,
 		}
 	}
 
-	if (enable && !is_enabled)
+	if (enable)
 		skl_power_well_post_enable(dev_priv, power_well);
 }
 
-- 
2.7.4