[PATCH v2 7/9] drm/panthor: Support GPU_CONTROL cache flush based on feature bit

Karunika Choo
2025-03-20T11:18:17Z

As the FLUSH_MEM and FLUSH_PT commands are deprecated in GPUs from
Mali-G720 onwards, this patch adds support for performing cache
maintenance via the FLUSH_CACHES command in GPU_CONTROL, in place of
FLUSH_MEM and FLUSH_PT based on PANTHOR_HW_FEATURE_GPU_CTRL_CACHE_FLUSH
feature bit.

Signed-off-by: Karunika Choo <karunika.choo@arm.com>
---
drivers/gpu/drm/panthor/panthor_hw.h | 6 +++++
drivers/gpu/drm/panthor/panthor_mmu.c | 35 +++++++++++++++++++++++++++
2 files changed, 41 insertions(+)

diff --git a/drivers/gpu/drm/panthor/panthor_hw.h b/drivers/gpu/drm/panthor/panthor_hw.h
index dfe0f86c5d76..4d67fdfe86f9 100644
--- a/drivers/gpu/drm/panthor/panthor_hw.h
+++ b/drivers/gpu/drm/panthor/panthor_hw.h
@@ -16,6 +16,12 @@ struct panthor_device;
* New feature flags will be added with support for newer GPU architectures.
*/
enum panthor_hw_feature {
+ /**
+ * @PANTHOR_HW_FEATURE_GPU_CTRL_CACHE_FLUSH: Perform cache maintenance
+ * via GPU_CONTROL.
+ */
+ PANTHOR_HW_FEATURE_GPU_CTRL_CACHE_FLUSH,
+
/** @PANTHOR_HW_FEATURES_END: Must be last. */
PANTHOR_HW_FEATURES_END
};
diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index a0a79f19bdea..4ac8bf36177e 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -29,7 +29,9 @@

#include "panthor_device.h"
#include "panthor_gem.h"
+#include "panthor_gpu.h"
#include "panthor_heap.h"
+#include "panthor_hw.h"
#include "panthor_mmu.h"
#include "panthor_regs.h"
#include "panthor_sched.h"
@@ -568,6 +570,35 @@ static void lock_region(struct panthor_device *ptdev, u32 as_nr,
write_cmd(ptdev, as_nr, AS_COMMAND_LOCK);
}

+static int mmu_hw_do_flush_on_gpu_ctrl(struct panthor_device *ptdev, int as_nr,
+ u32 op)
+{
+ const u32 l2_flush_op = CACHE_CLEAN | CACHE_INV;
+ u32 lsc_flush_op = 0;
+ int ret;
+
+ if (op == AS_COMMAND_FLUSH_MEM)
+ lsc_flush_op = CACHE_CLEAN | CACHE_INV;
+
+ ret = wait_ready(ptdev, as_nr);
+ if (ret)
+ return ret;
+
+ ret = panthor_gpu_flush_caches(ptdev, l2_flush_op, lsc_flush_op, 0);
+ if (ret)
+ return ret;
+
+ /*
+ * Explicitly unlock the region as the AS is not unlocked automatically
+ * at the end of the GPU_CONTROL cache flush command, unlike
+ * AS_COMMAND_FLUSH_MEM or AS_COMMAND_FLUSH_PT.
+ */
+ write_cmd(ptdev, as_nr, AS_COMMAND_UNLOCK);
+
+ /* Wait for the unlock command to complete */
+ return wait_ready(ptdev, as_nr);
+}
+
static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
u64 iova, u64 size, u32 op)
{
@@ -585,6 +616,10 @@ static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
if (op != AS_COMMAND_UNLOCK)
lock_region(ptdev, as_nr, iova, size);

+ if (panthor_hw_supports(ptdev,PANTHOR_HW_FEATURE_GPU_CTRL_CACHE_FLUSH))
+ if (op == AS_COMMAND_FLUSH_MEM || op == AS_COMMAND_FLUSH_PT)
+ return mmu_hw_do_flush_on_gpu_ctrl(ptdev, as_nr, op);
+
/* Run the MMU operation */
write_cmd(ptdev, as_nr, op);

--
2.47.1