[PATCH v5 01/10] drm/v3d: Fix the MMU flush order

[Maíra Canal]

We must first flush the MMU cache and then, flush the TLB, not the other
way around. Currently, we can see a race condition between the MMU cache
and the TLB when running multiple rendering processes at the same time.
This is evidenced by MMU errors triggered by the IRQ.

Fix the MMU flush order by flushing the MMU cache and then the TLB.

Fixes: 57692c94dcbe ("drm/v3d: Introduce a new DRM driver for Broadcom V3D V3.x+")
Signed-off-by: Maíra Canal <mcanal at igalia.com>
---
 drivers/gpu/drm/v3d/v3d_mmu.c | 29 ++++++++++-------------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/v3d/v3d_mmu.c b/drivers/gpu/drm/v3d/v3d_mmu.c
index 14f3af40d6f6..06bb44c7f35d 100644
--- a/drivers/gpu/drm/v3d/v3d_mmu.c
+++ b/drivers/gpu/drm/v3d/v3d_mmu.c
@@ -32,32 +32,23 @@ static int v3d_mmu_flush_all(struct v3d_dev *v3d)
 {
 	int ret;
 
-	/* Make sure that another flush isn't already running when we
-	 * start this one.
-	 */
-	ret = wait_for(!(V3D_READ(V3D_MMU_CTL) &
-			 V3D_MMU_CTL_TLB_CLEARING), 100);
-	if (ret)
-		dev_err(v3d->drm.dev, "TLB clear wait idle pre-wait failed\n");
-
-	V3D_WRITE(V3D_MMU_CTL, V3D_READ(V3D_MMU_CTL) |
-		  V3D_MMU_CTL_TLB_CLEAR);
-
-	V3D_WRITE(V3D_MMUC_CONTROL,
-		  V3D_MMUC_CONTROL_FLUSH |
+	V3D_WRITE(V3D_MMUC_CONTROL, V3D_MMUC_CONTROL_FLUSH |
 		  V3D_MMUC_CONTROL_ENABLE);
 
-	ret = wait_for(!(V3D_READ(V3D_MMU_CTL) &
-			 V3D_MMU_CTL_TLB_CLEARING), 100);
+	ret = wait_for(!(V3D_READ(V3D_MMUC_CONTROL) &
+			 V3D_MMUC_CONTROL_FLUSHING), 100);
 	if (ret) {
-		dev_err(v3d->drm.dev, "TLB clear wait idle failed\n");
+		dev_err(v3d->drm.dev, "MMUC flush wait idle failed\n");
 		return ret;
 	}
 
-	ret = wait_for(!(V3D_READ(V3D_MMUC_CONTROL) &
-			 V3D_MMUC_CONTROL_FLUSHING), 100);
+	V3D_WRITE(V3D_MMU_CTL, V3D_READ(V3D_MMU_CTL) |
+		  V3D_MMU_CTL_TLB_CLEAR);
+
+	ret = wait_for(!(V3D_READ(V3D_MMU_CTL) &
+			 V3D_MMU_CTL_TLB_CLEARING), 100);
 	if (ret)
-		dev_err(v3d->drm.dev, "MMUC flush wait idle failed\n");
+		dev_err(v3d->drm.dev, "TLB clear wait idle failed\n");
 
 	return ret;
 }
-- 
2.46.0