linux-kernel - [PATCH v2] drm/panthor: Simplify mmu_hw_do_operation

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Message-ID: <20250815134226.57703-1-steven.price@arm.com>
Date: Fri, 15 Aug 2025 14:42:24 +0100
From: Steven Price <steven.price@....com>
To: Boris Brezillon <boris.brezillon@...labora.com>,
	Liviu Dudau <liviu.dudau@....com>,
	Daniel Stone <daniel@...ishbar.org>
Cc: Steven Price <steven.price@....com>,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	Karunika Choo <karunika.choo@....com>,
	Chia-I Wu <olvaffe@...il.com>
Subject: [PATCH v2] drm/panthor: Simplify mmu_hw_do_operation_locked

The only callers to mmu_hw_do_operation_locked() pass an 'op' of either
AS_COMAND_FLUSH_MEM or AS_COMMAND_FLUSH_PT. This means the code paths
after that are dead. Removing those paths means the
mmu_hw_do_flush_on_gpu_ctrl() function might has well be inlined.

Simplify everything by having a switch statement for the type of 'op'
(warning if we get an unexpected value) and removing the dead cases.

Suggested-by: Daniel Stone <daniel@...ishbar.org>
Signed-off-by: Steven Price <steven.price@....com>
---
Changes from v1:
 * As well as removing dead code, inline mmu_hw_do_flush_on_gpu_ctrl

 drivers/gpu/drm/panthor/panthor_mmu.c | 57 ++++++++++++---------------
 1 file changed, 26 insertions(+), 31 deletions(-)

diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
index 367c89aca558..9d77e7c16ed2 100644
--- a/drivers/gpu/drm/panthor/panthor_mmu.c
+++ b/drivers/gpu/drm/panthor/panthor_mmu.c
@@ -569,15 +569,37 @@ 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)
+static int mmu_hw_do_operation_locked(struct panthor_device *ptdev, int as_nr,
+				      u64 iova, u64 size, u32 op)
 {
 	const u32 l2_flush_op = CACHE_CLEAN | CACHE_INV;
-	u32 lsc_flush_op = 0;
+	u32 lsc_flush_op;
 	int ret;
 
-	if (op == AS_COMMAND_FLUSH_MEM)
+	lockdep_assert_held(&ptdev->mmu->as.slots_lock);
+
+	switch (op) {
+	case AS_COMMAND_FLUSH_MEM:
 		lsc_flush_op = CACHE_CLEAN | CACHE_INV;
+		break;
+	case AS_COMMAND_FLUSH_PT:
+		lsc_flush_op = 0;
+		break;
+	default:
+		drm_WARN(&ptdev->base, 1, "Unexpected AS_COMMAND: %d", op);
+		return -EINVAL;
+	}
+
+	if (as_nr < 0)
+		return 0;
+
+	/*
+	 * If the AS number is greater than zero, then we can be sure
+	 * the device is up and running, so we don't need to explicitly
+	 * power it up
+	 */
+
+	lock_region(ptdev, as_nr, iova, size);
 
 	ret = wait_ready(ptdev, as_nr);
 	if (ret)
@@ -598,33 +620,6 @@ static int mmu_hw_do_flush_on_gpu_ctrl(struct panthor_device *ptdev, int as_nr,
 	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)
-{
-	lockdep_assert_held(&ptdev->mmu->as.slots_lock);
-
-	if (as_nr < 0)
-		return 0;
-
-	/*
-	 * If the AS number is greater than zero, then we can be sure
-	 * the device is up and running, so we don't need to explicitly
-	 * power it up
-	 */
-
-	if (op != AS_COMMAND_UNLOCK)
-		lock_region(ptdev, as_nr, iova, size);
-
-	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);
-
-	/* Wait for the flush to complete */
-	return wait_ready(ptdev, as_nr);
-}
-
 static int mmu_hw_do_operation(struct panthor_vm *vm,
 			       u64 iova, u64 size, u32 op)
 {
-- 
2.39.5