2021-09-29 21:44:49

by Brian Norris

Subject: [PATCH] drm/brdige: analogix_dp: Grab runtime PM reference for DP-AUX

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: <[email protected]>
Cc: Tomeu Vizoso <[email protected]>
Signed-off-by: Brian Norris <[email protected]>
---

.../gpu/drm/bridge/analogix/analogix_dp_core.c | 17 ++++++++++++++++-
1 file changed, 16 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..a1b553904b85 100644
--- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
+++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
@@ -1632,8 +1632,23 @@ 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_DEV_ERROR(dp->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_DEV_ERROR(dp->dev, "Failed to unprepare panel (%d)\n", ret2);
+
+ return ret;
}

struct analogix_dp_device *
--
2.33.0.685.g46640cef36-goog

2021-10-01 21:30:57

by Brian Norris

Subject: Re: [PATCH] drm/brdige: analogix_dp: Grab runtime PM reference for DP-AUX

On Fri, Oct 1, 2021 at 1:37 PM Sean Paul <[email protected]> wrote:
> On Wed, Sep 29, 2021 at 02:41:03PM -0700, Brian Norris wrote:
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > @@ -1632,8 +1632,23 @@ 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_DEV_ERROR(dp->dev, "Failed to prepare panel (%d)\n", ret);
>
> s/DRM_DEV_ERROR/drm_err/

Sure. Now that I'm looking a second time, I see the header recommends this.

> > + 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_DEV_ERROR(dp->dev, "Failed to unprepare panel (%d)\n", ret2);
>
> What's the reasoning for not propagating unprepare failures? I feel like that
> should be fair game.

I suppose the underlying reason is laziness, sorry. But a related
reason is the we probably should prefer propagating the
analogix_dp_transfer() error, if it's non-zero, rather than the
unprepare error. That's not too hard to do though, even if it's
slightly more awkward.

> > +
> > + return ret;
> > }
> >
> > struct analogix_dp_device *

v2 coming.

Regards,
Brian

2021-10-01 21:43:14

by Sean Paul

Subject: Re: [PATCH] drm/brdige: analogix_dp: Grab runtime PM reference for DP-AUX

On Wed, Sep 29, 2021 at 02:41:03PM -0700, 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: <[email protected]>
> Cc: Tomeu Vizoso <[email protected]>
> Signed-off-by: Brian Norris <[email protected]>
> ---
>
> .../gpu/drm/bridge/analogix/analogix_dp_core.c | 17 ++++++++++++++++-
> 1 file changed, 16 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..a1b553904b85 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -1632,8 +1632,23 @@ 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_DEV_ERROR(dp->dev, "Failed to prepare panel (%d)\n", ret);

s/DRM_DEV_ERROR/drm_err/

> + 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_DEV_ERROR(dp->dev, "Failed to unprepare panel (%d)\n", ret2);

What's the reasoning for not propagating unprepare failures? I feel like that
should be fair game.

> +
> + return ret;
> }
>
> struct analogix_dp_device *
> --
> 2.33.0.685.g46640cef36-goog
>

--
Sean Paul, Software Engineer, Google / Chromium OS