[PATCH 2/2] drm/i915: Handle GEN6_PMINTRMSK for proper masking of RPS interrupts with GuC submission

[Sagar Arun Kamble]

Driver needs to ensure that it doesn't mask the PM interrupts, which are
unmasked/needed by GuC firmware. For that, Driver maintains a bitmask of
interrupts to be kept enabled, pm_intr_keep.

By default, RP Up/Down Threshold Interrupt bits (and others) in
GEN6_PMINTRMSK register were unmasked (by BIOS) before GuC Load. Hence
Driver was keeping them unmasked always assuming GuC needed them.
As an optimization, Driver needs to mask these bits in order to
avoid redundant UP threshold interrupts when frequency is set to maximum,
RP0 or Down threshold interrupts when frequency is set to minimum, RPn.

This patch will mask all bits in GEN6_PMINTRMSK before GuC is loaded to
ensure pm_intr_keep reflects only interrupts that are needed by GuC. Post
GuC load, writing cur_freq will restore bits other than pm_intr_keep.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Sagar Arun Kamble <sagar.a.kamble at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c  | 13 +++++++++++++
 drivers/gpu/drm/i915/intel_drv.h |  1 +
 drivers/gpu/drm/i915/intel_pm.c  |  2 +-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1418c1c..cafb4d0 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4399,12 +4399,25 @@ i915_gem_init_hw(struct drm_device *dev)
 
 	intel_mocs_init_l3cc_table(dev);
 
+	/*
+	 * Mask all interrupts to know which interrupts are needed by GuC.
+	 * Restore host side interrupt masks post load.
+	*/
+	I915_WRITE(GEN6_PMINTRMSK, gen6_sanitize_rps_pm_mask(dev_priv, ~0u));
+
 	/* We can't enable contexts until all firmware is loaded */
 	ret = intel_guc_setup(dev);
 	if (ret)
 		goto out;
 
 out:
+	/*
+	 * Below write will ensure mask for RPS interrupts is restored back
+	 * w.r.t cur_freq, particularly post reset.
+	 */
+	I915_WRITE(GEN6_PMINTRMSK,
+		   gen6_rps_pm_mask(dev_priv, dev_priv->rps.cur_freq));
+
 	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
 	return ret;
 }
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 4bfb01c..431c17d 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1734,6 +1734,7 @@ void intel_enable_gt_powersave(struct drm_i915_private *dev_priv);
 void intel_autoenable_gt_powersave(struct drm_i915_private *dev_priv);
 void intel_disable_gt_powersave(struct drm_i915_private *dev_priv);
 void intel_suspend_gt_powersave(struct drm_i915_private *dev_priv);
+u32 gen6_rps_pm_mask(struct drm_i915_private *dev_priv, u8 val);
 void gen6_rps_busy(struct drm_i915_private *dev_priv);
 void gen6_rps_reset_ei(struct drm_i915_private *dev_priv);
 void gen6_rps_idle(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 57ded11..7c88acfa 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4878,7 +4878,7 @@ static void gen6_set_rps_thresholds(struct drm_i915_private *dev_priv, u8 val)
 	dev_priv->rps.last_adj = 0;
 }
 
-static u32 gen6_rps_pm_mask(struct drm_i915_private *dev_priv, u8 val)
+u32 gen6_rps_pm_mask(struct drm_i915_private *dev_priv, u8 val)
 {
 	u32 mask = 0;
 
-- 
1.9.1