drm/i915: Introduce intel_gt_mcr_lock_sanitize()

Implement intel_gt_mcr_lock_sanitize() to provide a mechanism
for cleaning the steer semaphore when absolutely necessary.

v2: remove unnecessary lock(Andi, Matt)
    improve the kernel doc(Matt)
    s/intel_gt_mcr_lock_clear/intel_gt_mcr_lock_sanitize
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230928130015.6758-1-nirmoy.das@intel.com

drivers/gpu/drm/i915/gt/intel_gt_mcr.c

@@ -419,6 +419,28 @@ void intel_gt_mcr_unlock(struct intel_gt *gt, unsigned long flags)
 		intel_uncore_write_fw(gt->uncore, MTL_STEER_SEMAPHORE, 0x1);
 }
 
+/**
+ * intel_gt_mcr_lock_sanitize - Sanitize MCR steering lock
+ * @gt: GT structure
+ *
+ * This will be used to sanitize the initial status of the hardware lock
+ * during driver load and resume since there won't be any concurrent access
+ * from other agents at those times, but it's possible that boot firmware
+ * may have left the lock in a bad state.
+ *
+ */
+void intel_gt_mcr_lock_sanitize(struct intel_gt *gt)
+{
+	/*
+	 * This gets called at load/resume time, so we shouldn't be
+	 * racing with other driver threads grabbing the mcr lock.
+	 */
+	lockdep_assert_not_held(&gt->mcr_lock);
+
+	if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70))
+		intel_uncore_write_fw(gt->uncore, MTL_STEER_SEMAPHORE, 0x1);
+}
+
 /**
  * intel_gt_mcr_read - read a specific instance of an MCR register
  * @gt: GT structure

drivers/gpu/drm/i915/gt/intel_gt_mcr.h

@@ -11,6 +11,7 @@
 void intel_gt_mcr_init(struct intel_gt *gt);
 void intel_gt_mcr_lock(struct intel_gt *gt, unsigned long *flags);
 void intel_gt_mcr_unlock(struct intel_gt *gt, unsigned long flags);
+void intel_gt_mcr_lock_sanitize(struct intel_gt *gt);
 
 u32 intel_gt_mcr_read(struct intel_gt *gt,
 		      i915_mcr_reg_t reg,