drm/radeon: Clear RB_OVERFLOW bit earlier

Otherwise the bit remains set in rdev->ih.rptr, so the wptr can never
match that and we still have an infinite loop.

This fix allows me to successfully recover from an IH ring buffer
overflow.
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/cik.c

@@ -7751,6 +7751,7 @@ static inline u32 cik_get_ih_wptr(struct radeon_device *rdev)
 		wptr = RREG32(IH_RB_WPTR);
 
 	if (wptr & RB_OVERFLOW) {
+		wptr &= ~RB_OVERFLOW;
 		/* When a ring buffer overflow happen start parsing interrupt
 		 * from the last not overwritten vector (wptr + 16). Hopefully
 		 * this should allow us to catchup.
@@ -7761,7 +7762,6 @@ static inline u32 cik_get_ih_wptr(struct radeon_device *rdev)
 		tmp = RREG32(IH_RB_CNTL);
 		tmp |= IH_WPTR_OVERFLOW_CLEAR;
 		WREG32(IH_RB_CNTL, tmp);
-		wptr &= ~RB_OVERFLOW;
 	}
 	return (wptr & rdev->ih.ptr_mask);
 }

drivers/gpu/drm/radeon/evergreen.c

@@ -4749,6 +4749,7 @@ static u32 evergreen_get_ih_wptr(struct radeon_device *rdev)
 		wptr = RREG32(IH_RB_WPTR);
 
 	if (wptr & RB_OVERFLOW) {
+		wptr &= ~RB_OVERFLOW;
 		/* When a ring buffer overflow happen start parsing interrupt
 		 * from the last not overwritten vector (wptr + 16). Hopefully
 		 * this should allow us to catchup.
@@ -4759,7 +4760,6 @@ static u32 evergreen_get_ih_wptr(struct radeon_device *rdev)
 		tmp = RREG32(IH_RB_CNTL);
 		tmp |= IH_WPTR_OVERFLOW_CLEAR;
 		WREG32(IH_RB_CNTL, tmp);
-		wptr &= ~RB_OVERFLOW;
 	}
 	return (wptr & rdev->ih.ptr_mask);
 }

drivers/gpu/drm/radeon/r600.c

@@ -3792,6 +3792,7 @@ static u32 r600_get_ih_wptr(struct radeon_device *rdev)
 		wptr = RREG32(IH_RB_WPTR);
 
 	if (wptr & RB_OVERFLOW) {
+		wptr &= ~RB_OVERFLOW;
 		/* When a ring buffer overflow happen start parsing interrupt
 		 * from the last not overwritten vector (wptr + 16). Hopefully
 		 * this should allow us to catchup.
@@ -3802,7 +3803,6 @@ static u32 r600_get_ih_wptr(struct radeon_device *rdev)
 		tmp = RREG32(IH_RB_CNTL);
 		tmp |= IH_WPTR_OVERFLOW_CLEAR;
 		WREG32(IH_RB_CNTL, tmp);
-		wptr &= ~RB_OVERFLOW;
 	}
 	return (wptr & rdev->ih.ptr_mask);
 }

drivers/gpu/drm/radeon/si.c

@@ -6316,6 +6316,7 @@ static inline u32 si_get_ih_wptr(struct radeon_device *rdev)
 		wptr = RREG32(IH_RB_WPTR);
 
 	if (wptr & RB_OVERFLOW) {
+		wptr &= ~RB_OVERFLOW;
 		/* When a ring buffer overflow happen start parsing interrupt
 		 * from the last not overwritten vector (wptr + 16). Hopefully
 		 * this should allow us to catchup.
@@ -6326,7 +6327,6 @@ static inline u32 si_get_ih_wptr(struct radeon_device *rdev)
 		tmp = RREG32(IH_RB_CNTL);
 		tmp |= IH_WPTR_OVERFLOW_CLEAR;
 		WREG32(IH_RB_CNTL, tmp);
-		wptr &= ~RB_OVERFLOW;
 	}
 	return (wptr & rdev->ih.ptr_mask);
 }