From: Doug Anderson <dianders@chromium.org>
To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>,
dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org,
Mikko Perttunen <mperttunen@nvidia.com>,
Jonathan Hunter <jonathanh@nvidia.com>,
Thierry Reding <thierry.reding@gmail.com>,
Ankit Nautiyal <ankit.k.nautiyal@intel.com>,
Daniel Vetter <daniel@ffwll.ch>,
David Airlie <airlied@gmail.com>,
Imre Deak <imre.deak@intel.com>,
Jani Nikula <jani.nikula@intel.com>,
Maxime Ripard <mripard@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/dp: Clarify that wait_hpd_asserted() is not optional for panels
Date: Tue, 19 Mar 2024 14:00:14 -0700 [thread overview]
Message-ID: <CAD=FV=W0k5U0i+Q_X_3HAviY-LXNrAw=PFjWDg+eej-Kq=0Y3w@mail.gmail.com> (raw)
In-Reply-To: <CAA8EJpoAwRKbHxVhi0q9koSUWFPcD4sP=F36r+rYsrtbY0fLkQ@mail.gmail.com>
Hi,
On Tue, Mar 19, 2024 at 1:55 PM Dmitry Baryshkov
<dmitry.baryshkov@linaro.org> wrote:
>
> > >>>> - * panel to finish powering on. This is an optional function.
> > >>>> + * panel to finish powering on. It is optional for DP AUX controllers
> > >>>> + * to implement this function but required for DP AUX endpoints (panel
> > >>>> + * drivers) to call it after powering up but before doing AUX transfers.
> > >>>> + * If a DP AUX controller does not implement this function then it
> > >>>> + * may still support eDP panels that use the AUX controller's built-in
> > >>>> + * HPD signal by implementing a long wait for HPD in the transfer()
> > >>>> + * callback, though this is deprecated.
> > >>>
> > >>> It doesn't cover a valid case when the panel driver handles HPD signal
> > >>> on its own.
> > >>>
> > >>
> > >> This doc is only for wait_for_hpd_asserted(). If panel driver handles
> > >> HPD signal on its own, this will not be called. Do we need a doc for that?
> > >
> > > This comment declares that this callback must be called by the panel
> > > driver: '...but required for DP AUX endpoints [...] to call it after
> > > powering up but before doing AUX transfers.'
> > >
> > > If we were to follow documentation changes from this patch, we'd have
> > > to patch panel-edp to always call wait_for_hpd_asserted, even if HPD
> > > GPIO is used. However this is not correct from my POV.
> > >
> >
> > hmmm I dont mind explicitly saying "unless the panel can independently
> > check the HPD state" but not required in my opinion because if panel was
> > capable of checking the HPD gpio (its self-capable) why would it even
> > call wait_for_hpd_asserted?
>
> I'm fine with the proposed change. Doug?
>
> >
> > I will let you and Doug discuss this but fwiw, I am fine without this
> > additional clarification. So the R-b stands with or without this
> > additional clause.
Adjusted wording in v2. Kept Abhniav's R-b. PTAL.
https://lore.kernel.org/r/20240319135836.v2.1.I521dad0693cc24fe4dd14cba0c7048d94f5b6b41@changeid
prev parent reply other threads:[~2024-03-19 21:00 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-19 18:14 [PATCH] drm/dp: Clarify that wait_hpd_asserted() is not optional for panels Douglas Anderson
2024-03-19 18:26 ` Abhinav Kumar
2024-03-19 18:35 ` Dmitry Baryshkov
2024-03-19 19:02 ` Abhinav Kumar
2024-03-19 20:16 ` Dmitry Baryshkov
2024-03-19 20:38 ` Abhinav Kumar
2024-03-19 20:54 ` Dmitry Baryshkov
2024-03-19 21:00 ` Doug Anderson [this message]
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