This is a note to let you know that I've just added the patch titled
drm/i915/mcr: Hold GT forcewake during steering operations
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-i915-mcr-hold-gt-forcewake-during-steering-opera.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 7bb19663c9d4e8e95f794c50d467e1fc1afbcec7
Author: Matt Roper <matthew.d.roper@xxxxxxxxx>
Date: Thu Oct 19 10:02:42 2023 -0700
drm/i915/mcr: Hold GT forcewake during steering operations
[ Upstream commit 78cc55e0b64c820673a796635daf82c7eadfe152 ]
The steering control and semaphore registers are inside an "always on"
power domain with respect to RC6. However there are some issues if
higher-level platform sleep states are entering/exiting at the same time
these registers are accessed. Grabbing GT forcewake and holding it over
the entire lock/steer/unlock cycle ensures that those sleep states have
been fully exited before we access these registers.
This is expected to become a formally documented/numbered workaround
soon.
Note that this patch alone isn't expected to have an immediately
noticeable impact on MCR (mis)behavior; an upcoming pcode firmware
update will also be necessary to provide the other half of this
workaround.
v2:
- Move the forcewake inside the Xe_LPG-specific IP version check. This
should only be necessary on platforms that have a steering semaphore.
Fixes: 3100240bf846 ("drm/i915/mtl: Add hardware-level lock for steering")
Cc: Radhakrishna Sripada <radhakrishna.sripada@xxxxxxxxx>
Cc: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx>
Signed-off-by: Matt Roper <matthew.d.roper@xxxxxxxxx>
Reviewed-by: Radhakrishna Sripada <radhakrishna.sripada@xxxxxxxxx>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@xxxxxxxxx>
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20231019170241.2102037-2-matthew.d.roper@xxxxxxxxx
(cherry picked from commit 8fa1c7cd1fe9cdfc426a603e1f1eecd3f463c487)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
index 0b414eae16831..2c0f1f3e28ff8 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
@@ -376,9 +376,26 @@ void intel_gt_mcr_lock(struct intel_gt *gt, unsigned long *flags)
* driver threads, but also with hardware/firmware agents. A dedicated
* locking register is used.
*/
- if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70))
+ if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70)) {
+ /*
+ * The steering control and semaphore registers are inside an
+ * "always on" power domain with respect to RC6. However there
+ * are some issues if higher-level platform sleep states are
+ * entering/exiting at the same time these registers are
+ * accessed. Grabbing GT forcewake and holding it over the
+ * entire lock/steer/unlock cycle ensures that those sleep
+ * states have been fully exited before we access these
+ * registers. This wakeref will be released in the unlock
+ * routine.
+ *
+ * This is expected to become a formally documented/numbered
+ * workaround soon.
+ */
+ intel_uncore_forcewake_get(gt->uncore, FORCEWAKE_GT);
+
err = wait_for(intel_uncore_read_fw(gt->uncore,
MTL_STEER_SEMAPHORE) == 0x1, 100);
+ }
/*
* Even on platforms with a hardware lock, we'll continue to grab
@@ -415,8 +432,11 @@ void intel_gt_mcr_unlock(struct intel_gt *gt, unsigned long flags)
{
spin_unlock_irqrestore(>->mcr_lock, flags);
- if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70))
+ if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70)) {
intel_uncore_write_fw(gt->uncore, MTL_STEER_SEMAPHORE, 0x1);
+
+ intel_uncore_forcewake_put(gt->uncore, FORCEWAKE_GT);
+ }
}
/**
