drm/v3d: Skip MMU flush if the device is currently off.

raspberrypi inclusion
category: feature
bugzilla: 50432

--------------------------------

If it's off, we know it will be reset on poweron, so the MMU won't
have any TLB cached from before this point.  Avoids failed waits for
MMU flush to reply.
Signed-off-by: NEric Anholt <eric@anholt.net>
(cherry picked from commit 3ee4e2e0a9e9587eacbb69b067bbc72ab2cdc47b)
Signed-off-by: NFang Yafen <yafen@iscas.ac.cn>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/gpu/drm/v3d/v3d_mmu.c

@@ -18,6 +18,8 @@
  * each client.  This is not yet implemented.
  */
 
+#include <linux/pm_runtime.h>
+
 #include "v3d_drv.h"
 #include "v3d_regs.h"
 
@@ -34,6 +36,14 @@ static int v3d_mmu_flush_all(struct v3d_dev *v3d)
 {
 	int ret;
 
+	/* Keep power on the device on until we're done with this
+	 * call, but skip the flush if the device is off and will be
+	 * reset when powered back on.
+	 */
+	ret = pm_runtime_get_if_in_use(v3d->dev);
+	if (ret == 0)
+		return 0;
+
 	/* Make sure that another flush isn't already running when we
 	 * start this one.
 	 */
@@ -61,6 +71,9 @@ static int v3d_mmu_flush_all(struct v3d_dev *v3d)
 	if (ret)
 		dev_err(v3d->drm.dev, "MMUC flush wait idle failed\n");
 
+	pm_runtime_mark_last_busy(v3d->dev);
+	pm_runtime_put_autosuspend(v3d->dev);
+
 	return ret;
 }