[PATCH v7 10/26] drm/i915/display: Do not take uncore lock in i915_get_vblank_counter

[Maarten Lankhorst <dev@lankhorst.se>]

This fixes a lockdep splat that occurs in the code that should be run
with interrupts disabled. The uncore lock should not be taken and
released repeatedly in a timing sensitive path.

Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
---
 drivers/gpu/drm/i915/display/intel_de.h       |  8 ++++++
 drivers/gpu/drm/i915/display/intel_vblank.c   |  4 +--
 drivers/gpu/drm/i915/intel_uncore.h           | 26 +++++++++++++------
 .../drm/xe/compat-i915-headers/intel_uncore.h |  7 +++++
 4 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_de.h b/drivers/gpu/drm/i915/display/intel_de.h
index f30f3f8ebee1d..8990c2c778efe 100644
--- a/drivers/gpu/drm/i915/display/intel_de.h
+++ b/drivers/gpu/drm/i915/display/intel_de.h
@@ -68,6 +68,14 @@ intel_de_read64_2x32(struct intel_display *display,
 	return val;
 }
 
+static inline u64
+intel_de_read64_2x32_fw(struct intel_display *display,
+			i915_reg_t lower_reg, i915_reg_t upper_reg)
+{
+	return intel_uncore_read64_2x32_fw(__to_uncore(display),
+					   lower_reg, upper_reg);
+}
+
 static inline void
 intel_de_posting_read(struct intel_display *display, i915_reg_t reg)
 {
diff --git a/drivers/gpu/drm/i915/display/intel_vblank.c b/drivers/gpu/drm/i915/display/intel_vblank.c
index e204c260b9aef..749127ae7794c 100644
--- a/drivers/gpu/drm/i915/display/intel_vblank.c
+++ b/drivers/gpu/drm/i915/display/intel_vblank.c
@@ -109,8 +109,8 @@ u32 i915_get_vblank_counter(struct drm_crtc *crtc)
 	 * we get a low value that's stable across two reads of the high
 	 * register.
 	 */
-	frame = intel_de_read64_2x32(display, PIPEFRAMEPIXEL(display, pipe),
-				     PIPEFRAME(display, pipe));
+	frame = intel_de_read64_2x32_fw(display, PIPEFRAMEPIXEL(display, pipe),
+				        PIPEFRAME(display, pipe));
 
 	pixel = frame & PIPE_PIXEL_MASK;
 	frame = (frame >> PIPE_FRAME_LOW_SHIFT) & 0xffffff;
diff --git a/drivers/gpu/drm/i915/intel_uncore.h b/drivers/gpu/drm/i915/intel_uncore.h
index fafc2ca9a2376..507398a562649 100644
--- a/drivers/gpu/drm/i915/intel_uncore.h
+++ b/drivers/gpu/drm/i915/intel_uncore.h
@@ -449,13 +449,28 @@ static inline void intel_uncore_rmw_fw(struct intel_uncore *uncore,
 		intel_uncore_write_fw(uncore, reg, val);
 }
 
+static inline u64
+intel_uncore_read64_2x32_fw(struct intel_uncore *uncore,
+			    i915_reg_t lower_reg, i915_reg_t upper_reg)
+{
+	u32 upper, lower, old_upper, loop = 0;
+	upper = intel_uncore_read_fw(uncore, upper_reg);
+	do {
+		old_upper = upper;
+		lower = intel_uncore_read_fw(uncore, lower_reg);
+		upper = intel_uncore_read_fw(uncore, upper_reg);
+	} while (upper != old_upper && loop++ < 2);
+
+	return (u64)upper << 32 | lower;
+}
+
 static inline u64
 intel_uncore_read64_2x32(struct intel_uncore *uncore,
 			 i915_reg_t lower_reg, i915_reg_t upper_reg)
 {
-	u32 upper, lower, old_upper, loop = 0;
 	enum forcewake_domains fw_domains;
 	unsigned long flags;
+	u64 ret;
 
 	fw_domains = intel_uncore_forcewake_for_reg(uncore, lower_reg,
 						    FW_REG_READ);
@@ -466,17 +481,12 @@ intel_uncore_read64_2x32(struct intel_uncore *uncore,
 	spin_lock_irqsave(&uncore->lock, flags);
 	intel_uncore_forcewake_get__locked(uncore, fw_domains);
 
-	upper = intel_uncore_read_fw(uncore, upper_reg);
-	do {
-		old_upper = upper;
-		lower = intel_uncore_read_fw(uncore, lower_reg);
-		upper = intel_uncore_read_fw(uncore, upper_reg);
-	} while (upper != old_upper && loop++ < 2);
+	ret = intel_uncore_read64_2x32_fw(uncore, lower_reg, upper_reg);
 
 	intel_uncore_forcewake_put__locked(uncore, fw_domains);
 	spin_unlock_irqrestore(&uncore->lock, flags);
 
-	return (u64)upper << 32 | lower;
+	return ret;
 }
 
 static inline int intel_uncore_write_and_verify(struct intel_uncore *uncore,
diff --git a/drivers/gpu/drm/xe/compat-i915-headers/intel_uncore.h b/drivers/gpu/drm/xe/compat-i915-headers/intel_uncore.h
index a8cfd65119e09..6959a761fa06a 100644
--- a/drivers/gpu/drm/xe/compat-i915-headers/intel_uncore.h
+++ b/drivers/gpu/drm/xe/compat-i915-headers/intel_uncore.h
@@ -74,6 +74,13 @@ intel_uncore_read64_2x32(struct intel_uncore *uncore,
 	return (u64)upper << 32 | lower;
 }
 
+static inline u64
+intel_uncore_read64_2x32_fw(struct intel_uncore *uncore,
+			    i915_reg_t i915_lower_reg, i915_reg_t i915_upper_reg)
+{
+	return intel_uncore_read64_2x32(uncore, i915_lower_reg, i915_upper_reg);
+}
+
 static inline void intel_uncore_posting_read(struct intel_uncore *uncore,
 					     i915_reg_t i915_reg)
 {
-- 
2.51.0