drm/panthor: Always wait after sending a command to an AS

[ Upstream commit d2c6fde ]

There's currently no situation where we want to issue a command to an
AS and not wait for this command to complete. The wait is either
explicitly done (LOCK, UNLOCK) or it's missing (UPDATE). So let's
turn write_cmd() into as_send_cmd_and_wait() that has the wait after
a command is sent.

v2:
- New patch

v3:
- Collect R-b

v4:
- No changes

Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251128084841.3804658-2-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: bbrezillon

drivers/gpu/drm/panthor/panthor_mmu.c

@@ -523,27 +523,29 @@ static int wait_ready(struct panthor_device *ptdev, u32 as_nr)
 	return ret;
 }
 
-static int write_cmd(struct panthor_device *ptdev, u32 as_nr, u32 cmd)
+static int as_send_cmd_and_wait(struct panthor_device *ptdev, u32 as_nr, u32 cmd)
 {
 	int status;
 
 	/* write AS_COMMAND when MMU is ready to accept another command */
 	status = wait_ready(ptdev, as_nr);
-	if (!status)
+	if (!status) {
 		gpu_write(ptdev, AS_COMMAND(as_nr), cmd);
+		status = wait_ready(ptdev, as_nr);
+	}
 
 	return status;
 }
 
-static void lock_region(struct panthor_device *ptdev, u32 as_nr,
-			u64 region_start, u64 size)
+static int lock_region(struct panthor_device *ptdev, u32 as_nr,
+		       u64 region_start, u64 size)
 {
 	u8 region_width;
 	u64 region;
 	u64 region_end = region_start + size;
 
 	if (!size)
-		return;
+		return 0;
 
 	/*
 	 * The locked region is a naturally aligned power of 2 block encoded as
@@ -566,7 +568,7 @@ static void lock_region(struct panthor_device *ptdev, u32 as_nr,
 
 	/* Lock the region that needs to be updated */
 	gpu_write64(ptdev, AS_LOCKADDR(as_nr), region);
-	write_cmd(ptdev, as_nr, AS_COMMAND_LOCK);
+	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_LOCK);
 }
 
 static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
@@ -599,9 +601,7 @@ static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
 	 * power it up
 	 */
 
-	lock_region(ptdev, as_nr, iova, size);
-
-	ret = wait_ready(ptdev, as_nr);
+	ret = lock_region(ptdev, as_nr, iova, size);
 	if (ret)
 		return ret;
 
@@ -614,10 +614,7 @@ static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
 	 * 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);
+	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UNLOCK);
 }
 
 static int mmu_hw_do_operation(struct panthor_vm *vm,
@@ -646,7 +643,7 @@ static int panthor_mmu_as_enable(struct panthor_device *ptdev, u32 as_nr,
 	gpu_write64(ptdev, AS_MEMATTR(as_nr), memattr);
 	gpu_write64(ptdev, AS_TRANSCFG(as_nr), transcfg);
 
-	return write_cmd(ptdev, as_nr, AS_COMMAND_UPDATE);
+	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE);
 }
 
 static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr)
@@ -661,7 +658,7 @@ static int panthor_mmu_as_disable(struct panthor_device *ptdev, u32 as_nr)
 	gpu_write64(ptdev, AS_MEMATTR(as_nr), 0);
 	gpu_write64(ptdev, AS_TRANSCFG(as_nr), AS_TRANSCFG_ADRMODE_UNMAPPED);
 
-	return write_cmd(ptdev, as_nr, AS_COMMAND_UPDATE);
+	return as_send_cmd_and_wait(ptdev, as_nr, AS_COMMAND_UPDATE);
 }
 
 static u32 panthor_mmu_fault_mask(struct panthor_device *ptdev, u32 value)