[PATCH v2] drm/i915: Add an option to disable SAGV

[Azhar Shaikh <azhar.shaikh@intel.com>]

On Gen9 systems, with SAGV enabled, we have seen display
corruption(screenshots attached in the bug) which eventually lead to a
system hang. This happens when we have overlay plane and on enabling
and disabling the overlay plane. When the system hangs, we do not have
enough logs or information to debug the issue.
Having a module parameter will help in debugging the system hang.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=104975
Signed-off-by: Azhar Shaikh <azhar.shaikh@intel.com>
---
Changes from v1:
- Update the title and commit message.
- Rename the module param to enable_sagv and set it to default true.

 drivers/gpu/drm/i915/i915_params.c | 3 +++
 drivers/gpu/drm/i915/i915_params.h | 3 ++-
 drivers/gpu/drm/i915/intel_pm.c    | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index 08108ce5be21..88610720334e 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -167,6 +167,9 @@ struct i915_params i915_modparams __read_mostly = {
 i915_param_named_unsafe(enable_dp_mst, bool, 0600,
 	"Enable multi-stream transport (MST) for new DisplayPort sinks. (default: true)");
 
+i915_param_named_unsafe(enable_sagv, bool, 0600,
+	"Enable SAGV (default: true)");
+
 #if IS_ENABLED(CONFIG_DRM_I915_DEBUG)
 i915_param_named_unsafe(inject_load_failure, uint, 0400,
 	"Force an error after a number of failure check points (0:disabled (default), N:force failure at the Nth failure check point)");
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 430f5f9d0ff4..507d231b0ca6 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -69,7 +69,8 @@
 	param(bool, nuclear_pageflip, false) \
 	param(bool, enable_dp_mst, true) \
 	param(bool, enable_dpcd_backlight, false) \
-	param(bool, enable_gvt, false)
+	param(bool, enable_gvt, false) \
+	param(bool, enable_sagv, true)
 
 #define MEMBER(T, member, ...) T member;
 struct i915_params {
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 21dac6ebc202..4ac94045cc08 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3693,7 +3693,7 @@ bool intel_can_enable_sagv(struct drm_atomic_state *state)
 	int level, latency;
 	int sagv_block_time_us;
 
-	if (!intel_has_sagv(dev_priv))
+	if (!intel_has_sagv(dev_priv) || !i915_modparams.enable_sagv)
 		return false;
 
 	if (IS_GEN9(dev_priv))
-- 
1.9.1

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