Quoting Rob Clark (2022-01-06 10:14:46)
> From: Rob Clark <robdcl...@chromium.org>
>
> System suspend uses pm_runtime_force_suspend(), which cheekily bypasses
> the runpm reference counts. This doesn't actually work so well when the
> GPU is active. So add a reasonable delay waiting for the GPU to become
> idle.
Maybe also say:
Failure to wait during system wide suspend leads to GPU hangs seen on
resume.
>
> Alternatively we could just return -EBUSY in this case, but that has the
> disadvantage of causing system suspend to fail.
>
> Signed-off-by: Rob Clark <robdcl...@chromium.org>
> ---
> drivers/gpu/drm/msm/adreno/adreno_device.c | 9 +++++++++
> drivers/gpu/drm/msm/msm_gpu.c | 3 +++
> drivers/gpu/drm/msm/msm_gpu.h | 3 +++
> 3 files changed, 15 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c
> b/drivers/gpu/drm/msm/adreno/adreno_device.c
> index 93005839b5da..b677ca3fd75e 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> @@ -611,6 +611,15 @@ static int adreno_resume(struct device *dev)
> static int adreno_suspend(struct device *dev)
> {
> struct msm_gpu *gpu = dev_to_gpu(dev);
> + int ret = 0;
Please don't assign and then immediately overwrite.
> +
> + ret = wait_event_timeout(gpu->retire_event,
> + !msm_gpu_active(gpu),
> + msecs_to_jiffies(1000));
> + if (ret == 0) {
The usual pattern is
long timeleft;
timeleft = wait_event_timeout(...)
if (!timeleft) {
/* no time left; timed out */
Can it be the same pattern here? It helps because people sometimes
forget that wait_event_timeout() returns the time that is left and not
an error code when it times out.
> + dev_err(dev, "Timeout waiting for GPU to suspend\n");
> + return -EBUSY;
> + }
>
> return gpu->funcs->pm_suspend(gpu);
> }
