[Intel-gfx] [PATCH 1/1] drm/i915/gen9: Check BIOS RC6 setup before enabling RC6

[Sagar Arun Kamble]

RC6 setup is shared between BIOS and Driver. BIOS sets up subset of RC6
configuration registers. If those are not setup Driver should not enable RC6.
For implementing this, driver can check RC_CTRL0 and RC_CTRL1 values
to know if BIOS has enabled HW/SW RC6.
This will also enable user to control RC6 using BIOS settings alone.

Change-Id: If89518708e133be6b3c7c6f90869fb66224b7b87
Signed-off-by: Sagar Arun Kamble <sagar.a.kamble at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 9dda3ea..8c595e0 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4836,6 +4836,15 @@ static void gen8_enable_rps(struct drm_device *dev)
 	struct intel_engine_cs *ring;
 	uint32_t rc6_mask = 0;
 	int unused;
+	bool hw_rc6_enabled, sw_rc6_enabled;
+
+	/* Check if BIOS has enabled HW/SW RC6. Only then enable RC6 */
+	hw_rc6_enabled = I915_READ(GEN6_RC_CONTROL) &
+				(GEN6_RC_CTL_RC6_ENABLE | GEN6_RC_CTL_HW_ENABLE);
+	sw_rc6_enabled = !(I915_READ(GEN6_RC_CONTROL) & GEN6_RC_CTL_HW_ENABLE)
+				&& (I915_READ(GEN6_RC_STATE) & 0x40000);
+	if (!(hw_rc6_enabled || sw_rc6_enabled))
+		i915.enable_rc6 = 0;
 
 	/* 1a: Software RC state - RC0 */
 	I915_WRITE(GEN6_RC_STATE, 0);
-- 
1.9.1