linux-kernel - [PATCH] media: aspeed: Fix dram hang at res-change

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Message-ID: <20251124-video_dram_reset-v1-1-9d37229e4ec5@aspeedtech.com>
Date: Mon, 24 Nov 2025 11:05:14 +0800
From: Jammy Huang <jammy_huang@...eedtech.com>
To: Eddie James <eajames@...ux.ibm.com>, Mauro Carvalho Chehab
	<mchehab@...nel.org>, Joel Stanley <joel@....id.au>, Andrew Jeffery
	<andrew@...econstruct.com.au>, Philipp Zabel <p.zabel@...gutronix.de>
CC: <linux-media@...r.kernel.org>, <openbmc@...ts.ozlabs.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-aspeed@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>, Jammy Huang <jammy_huang@...eedtech.com>
Subject: [PATCH] media: aspeed: Fix dram hang at res-change

Dram hang could happen in the steps below:
1. start capture/compression
2. out-of-lock watchdog raise irq because of res-change.
3. aspeed_video_irq_res_change do clk-off

At step3, capture/compression could be not accomplished yet. If clk-off
in the middle of video operation, dram controller could hang at ast2500.

Use reset rather than clk-off/on to avoid this problem.

Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
---
On Aspeed KVM testing, we found it could lead to dram-hang if
res-change. Although the issue rarely happens, the impact is serious.

To avoid this issue, we use reset only rathar than clk-off/on in
res-change to avoid this issue.
---
 drivers/media/platform/aspeed/aspeed-video.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/media/platform/aspeed/aspeed-video.c b/drivers/media/platform/aspeed/aspeed-video.c
index b83e432452..41cb96f601 100644
--- a/drivers/media/platform/aspeed/aspeed-video.c
+++ b/drivers/media/platform/aspeed/aspeed-video.c
@@ -26,6 +26,7 @@
 #include <linux/workqueue.h>
 #include <linux/debugfs.h>
 #include <linux/ktime.h>
+#include <linux/reset.h>
 #include <linux/regmap.h>
 #include <linux/mfd/syscon.h>
 #include <media/v4l2-ctrls.h>
@@ -310,6 +311,7 @@ struct aspeed_video {
 	void __iomem *base;
 	struct clk *eclk;
 	struct clk *vclk;
+	struct reset_control *reset;
 
 	struct device *dev;
 	struct v4l2_ctrl_handler ctrl_handler;
@@ -720,6 +722,13 @@ static void aspeed_video_on(struct aspeed_video *video)
 	set_bit(VIDEO_CLOCKS_ON, &video->flags);
 }
 
+static void aspeed_video_reset(struct aspeed_video *v)
+{
+	reset_control_assert(v->reset);
+	usleep_range(100, 150);
+	reset_control_deassert(v->reset);
+}
+
 static void aspeed_video_bufs_done(struct aspeed_video *video,
 				   enum vb2_buffer_state state)
 {
@@ -742,7 +751,9 @@ static void aspeed_video_irq_res_change(struct aspeed_video *video, ulong delay)
 
 	video->v4l2_input_status = V4L2_IN_ST_NO_SIGNAL;
 
-	aspeed_video_off(video);
+	aspeed_video_write(video, VE_INTERRUPT_CTRL, 0);
+	aspeed_video_write(video, VE_INTERRUPT_STATUS, 0xffffffff);
+	aspeed_video_reset(video);
 	aspeed_video_bufs_done(video, VB2_BUF_STATE_ERROR);
 
 	schedule_delayed_work(&video->res_work, delay);
@@ -1984,8 +1995,7 @@ static void aspeed_video_stop_streaming(struct vb2_queue *q)
 		 * Need to force stop any DMA and try and get HW into a good
 		 * state for future calls to start streaming again.
 		 */
-		aspeed_video_off(video);
-		aspeed_video_on(video);
+		aspeed_video_reset(video);
 
 		aspeed_video_init_regs(video);
 
@@ -2230,6 +2240,12 @@ static int aspeed_video_init(struct aspeed_video *video)
 	}
 	dev_info(video->dev, "irq %d\n", irq);
 
+	video->reset = devm_reset_control_get(dev, NULL);
+	if (IS_ERR(video->reset)) {
+		dev_err(dev, "Unable to get reset\n");
+		return PTR_ERR(video->reset);
+	}
+
 	video->eclk = devm_clk_get(dev, "eclk");
 	if (IS_ERR(video->eclk)) {
 		dev_err(dev, "Unable to get ECLK\n");

---
base-commit: ac3fd01e4c1efce8f2c054cdeb2ddd2fc0fb150d
change-id: 20251124-video_dram_reset-c531f6ba573f

Best regards,
-- 
Jammy Huang <jammy_huang@...eedtech.com>