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@xxxxxxxxxxxxxxx>
Cc: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
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 *
