From: Michael Chang zhang971090220@gmail.com
[ Upstream commit 497f1fb94759fa0c638f15c12b1ab3e586bccfcb ]
Fix the issue when start_frame and detect_resolution functions are executed at the same time, which may cause driver stops capturing due to status of no video signal error.
Signed-off-by: Michael Chang zhang971090220@gmail.com Signed-off-by: Hans Verkuil hverkuil@xs4all.nl Signed-off-by: Sasha Levin sashal@kernel.org ---
Now let me analyze this commit based on the provided information: **YES** This commit should be backported to stable kernel trees based on the following analysis: 1. **Bug Fix Nature**: The commit specifically addresses a driver stuck issue caused by a race condition between the `start_frame` and `detect_resolution` functions. This is a clear bugfix that affects the operational functionality of the driver. 2. **User Impact**: When this race condition occurs, the driver stops capturing completely due to a "no video signal error" - this directly impacts users who rely on the video capture functionality. 3. **Minimal and Contained Changes**: The fix makes only a small, targeted change to the `npcm_video_detect_resolution()` function in `drivers/media/platform/nuvoton/npcm-video.c`. Specifically: - Removes the premature setting of `video->v4l2_input_status = V4L2_IN_ST_NO_SIGNAL` at the beginning - Only sets this status flag when the resolution is actually invalid (width/height are 0) - Adds proper debugging messages for both valid and invalid resolution cases 4. **Low Risk**: The change is logical and safe - instead of immediately assuming "no signal" and then potentially overriding it later, the code now only sets the "no signal" status when there's actually an invalid resolution detected. This eliminates the race condition without introducing new complexity. 5. **Similar Pattern to Backported Commits**: Looking at the reference commits, this follows the same pattern as "Similar Commit #1" (marked YES) which also fixed reference handling issues in the same driver. Both commits: - Fix driver-specific bugs - Make small, contained changes - Address operational issues that affect users - Don't introduce new features or architectural changes 6. **Race Condition Fix**: Race condition fixes are typically good candidates for stable backporting as they address timing-dependent bugs that can be difficult to diagnose and significantly impact system reliability. The fix addresses a specific functional bug where the driver could get stuck due to improper status flag handling during concurrent operations, making it an appropriate candidate for stable tree inclusion.
drivers/media/platform/nuvoton/npcm-video.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/drivers/media/platform/nuvoton/npcm-video.c b/drivers/media/platform/nuvoton/npcm-video.c index e0dee768a3be1..28d3e1e289e05 100644 --- a/drivers/media/platform/nuvoton/npcm-video.c +++ b/drivers/media/platform/nuvoton/npcm-video.c @@ -863,7 +863,6 @@ static void npcm_video_detect_resolution(struct npcm_video *video) struct regmap *gfxi = video->gfx_regmap; unsigned int dispst;
- video->v4l2_input_status = V4L2_IN_ST_NO_SIGNAL; det->width = npcm_video_hres(video); det->height = npcm_video_vres(video);
@@ -892,12 +891,16 @@ static void npcm_video_detect_resolution(struct npcm_video *video) clear_bit(VIDEO_RES_CHANGING, &video->flags); }
- if (det->width && det->height) + if (det->width && det->height) { video->v4l2_input_status = 0; - - dev_dbg(video->dev, "Got resolution[%dx%d] -> [%dx%d], status %d\n", - act->width, act->height, det->width, det->height, - video->v4l2_input_status); + dev_dbg(video->dev, "Got resolution[%dx%d] -> [%dx%d], status %d\n", + act->width, act->height, det->width, det->height, + video->v4l2_input_status); + } else { + video->v4l2_input_status = V4L2_IN_ST_NO_SIGNAL; + dev_err(video->dev, "Got invalid resolution[%dx%d]\n", det->width, + det->height); + } }
static int npcm_video_set_resolution(struct npcm_video *video,