Hi Brian,
I am not DP specialist so CC-ed people working with DP
On 01.10.2021 23:42, Brian Norris wrote:
If the display is not enable()d, then we aren't holding a runtime PM reference here. Thus, it's easy to accidentally cause a hang, if user space is poking around at /dev/drm_dp_aux0 at the "wrong" time.
Let's get the panel and PM state right before trying to talk AUX.
Fixes: 0d97ad03f422 ("drm/bridge: analogix_dp: Remove duplicated code") Cc: stable@vger.kernel.org Cc: Tomeu Vizoso tomeu.vizoso@collabora.com Signed-off-by: Brian Norris briannorris@chromium.org
Few questions/issues here:
1. If it is just to avoid accidental 'hangs' it would be better to just check if the panel is working before transfer, if not, return error code. If there is better reason for this pm dance, please provide it in description.
2. Again I see an assumption that panel-prepare enables power for something different than video transmission, accidentally it is true for most devices, but devices having more fine grained power management will break, or at least will be used inefficiently - but maybe in case of dp it is OK ???
3. More general issue - I am not sure if this should not be handled uniformly for all drm_dp devices.
Regards
Andrzej
Changes in v2:
Fix spelling in Subject
DRM_DEV_ERROR() -> drm_err()
Propagate errors from un-analogix_dp_prepare_panel()
.../drm/bridge/analogix/analogix_dp_core.c | 21 ++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c index b7d2e4449cfa..6fc46ac93ef8 100644 --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c @@ -1632,8 +1632,27 @@ static ssize_t analogix_dpaux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg) { struct analogix_dp_device *dp = to_dp(aux);
- int ret, ret2;
- return analogix_dp_transfer(dp, msg);
- ret = analogix_dp_prepare_panel(dp, true, false);
- if (ret) {
drm_err(dp->drm_dev, "Failed to prepare panel (%d)\n", ret);return ret;- }
- pm_runtime_get_sync(dp->dev);
- ret = analogix_dp_transfer(dp, msg);
- pm_runtime_put(dp->dev);
- ret2 = analogix_dp_prepare_panel(dp, false, false);
- if (ret2) {
drm_err(dp->drm_dev, "Failed to unprepare panel (%d)\n", ret2);/* Prefer the analogix_dp_transfer() error, if it exists. */if (!ret)ret = ret2;- }
- return ret; }
struct analogix_dp_device *