[PATCH 1/4] drm/v3d: Wait for pending L2T flush before cleaning caches

[Maíra Canal <mcanal@igalia.com>]

v3d_clean_caches() starts the cache-clean sequence by writing
V3D_L2TCACTL_TMUWCF to V3D_CTL_L2TCACTL and then polling for that bit to
clear. It does not, however, check for an L2T flush (L2TFLS) that may
still be in flight from a previous operation.

On pre-V3D 7.1 hardware, kicking off the TMU write-combiner flush while an
L2T flush is still pending can clobber bits in L2TCACTL and cause cache
inconsistencies.

Poll for L2TFLS to clear before writing L2TCACTL on V3D < 7.1, ensuring
any pending flush has completed before a new clean is issued.

Cc: stable@vger.kernel.org
Fixes: d223f98f0209 ("drm/v3d: Add support for compute shader dispatch.")
Signed-off-by: Maíra Canal <mcanal@igalia.com>
---
 drivers/gpu/drm/v3d/v3d_gem.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
index 1ee3c038d5f6..c43d9af41374 100644
--- a/drivers/gpu/drm/v3d/v3d_gem.c
+++ b/drivers/gpu/drm/v3d/v3d_gem.c
@@ -206,6 +206,14 @@ v3d_clean_caches(struct v3d_dev *v3d)
 
 	trace_v3d_cache_clean_begin(dev);
 
+	/* GFXH-1897: Ensure pending flushes complete before writing L2TCACTL */
+	if (v3d->ver < V3D_GEN_71) {
+		if (wait_for(!(V3D_CORE_READ(core, V3D_CTL_L2TCACTL) &
+			       V3D_L2TCACTL_L2TFLS), 100)) {
+			drm_err(dev, "Timeout waiting for L2T clean\n");
+		}
+	}
+
 	V3D_CORE_WRITE(core, V3D_CTL_L2TCACTL, V3D_L2TCACTL_TMUWCF);
 	if (wait_for(!(V3D_CORE_READ(core, V3D_CTL_L2TCACTL) &
 		       V3D_L2TCACTL_TMUWCF), 100)) {

-- 
2.54.0