From: Lyude Paul <lyude@redhat.com>
To: Dmitry Osipenko <digetx@gmail.com>,
Thierry Reding <thierry.reding@gmail.com>
Cc: Jonathan Hunter <jonathanh@nvidia.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>,
Thomas Graichen <thomas.graichen@gmail.com>,
dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/2] drm/tegra: Use drm_dp_aux_register_ddc/chardev() helpers
Date: Fri, 12 Nov 2021 15:26:53 -0500 [thread overview]
Message-ID: <be1833c5d27e666b760c729fc112d1bbd7b7a269.camel@redhat.com> (raw)
In-Reply-To: <5ee3f964-39ec-f6e2-5a01-230532a8b17e@gmail.com>
On Fri, 2021-11-12 at 17:32 +0300, Dmitry Osipenko wrote:
> 12.11.2021 13:52, Thierry Reding пишет:
> > On Tue, Nov 09, 2021 at 05:39:02PM +0300, Dmitry Osipenko wrote:
> > > 09.11.2021 17:17, Dmitry Osipenko пишет:
> > > > 09.11.2021 17:08, Dmitry Osipenko пишет:
> > > > > > +static void host1x_drm_dev_deinit(struct host1x_device *dev)
> > > > > > +{
> > > > > > + struct drm_device *drm = dev_get_drvdata(&dev->dev);
> > > > > And platform_unregister_drivers() should be moved here.
> > > > >
> > > >
> > > > Nah, that should cause deadlock. This ad-hoc is too lame.
> > >
> > > Actually, there is no problem here as I see now. The host1x driver
> > > populates DT nodes after host1x_register() [1], meaning that Host1x DRM
> > > will be always inited first.
> > >
> > > [1]
> > > https://elixir.bootlin.com/linux/v5.15/source/drivers/gpu/host1x/dev.c#L475
> > >
> > > Still I'm not a fan of the ad-hoc solution.
> >
> > Could we not fix this by making the panel "hot-pluggable"? I don't think
> > there's anything inherent to the driver that would prevent doing so. The
> > original reason for why things are as intertwined as they are now is
> > because back at the time deferred framebuffer creation didn't exist. In
> > fact I added deferred framebuffer support with Daniel's help precisely
> > to fix a similar issue for things like HDMI and DP.
>
> I don't understand what do you mean by "hot-pluggable", panel is static.
> Please either clarify more or type the patch.
>
> Keep in mind that fix should be simple and portable because stable
> kernels are wrecked.
>
> > With HDMI and DP it's slightly less critical, because a lack of mode
> > support would've created a 1024x768 framebuffer, which most HDMI/DP
> > monitors support. However, with panels we need to ensure that the exact
> > mode from the panel is used to create the framebuffer, so it can only be
> > created when the panel is available.
> >
> > But, given that deferred framebuffer creation works now (which allows
> > the framebuffer console to show up at the preferred resolution for HDMI
> > and DP), even if a monitor is attached only after the driver has probed
> > already, we should be able to make something like that work with panels
> > as well.
>
> BTW, I see now that DPAUX I2C transfer helper may access
> aux->drm_device. Hence v1 patch isn't correct anyways.
JFYI - unless I'm misunderstanding you, the aux->drm_dev accesses in the DPAUX
i2c transfer functions are just from the various drm_{dbg,err,etc.} calls,
which means that they all should be able to handle aux->drm_dev being NULL. If
you can set aux->drm_dev before i2c transfers start that's more ideal, since
otherwise you'll see the AUX device name as "(null)" in the kernel log, but
any point before device registration should work.
>
> For now I'll try to test more the ad-hoc variant with Thomas and send it
> as v2 if we won't have a better solution.
>
--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat
next prev parent reply other threads:[~2021-11-12 20:27 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-07 23:08 [PATCH v1 1/2] drm/dp: Add drm_dp_aux_register_ddc/chardev() helpers Dmitry Osipenko
2021-11-07 23:08 ` [PATCH v1 2/2] drm/tegra: Use " Dmitry Osipenko
2021-11-08 15:17 ` Daniel Vetter
2021-11-08 18:16 ` Dmitry Osipenko
2021-11-09 9:19 ` Daniel Vetter
2021-11-09 13:52 ` Dmitry Osipenko
2021-11-09 14:08 ` Dmitry Osipenko
2021-11-09 14:17 ` Dmitry Osipenko
2021-11-09 14:39 ` Dmitry Osipenko
2021-11-12 10:52 ` Thierry Reding
2021-11-12 14:32 ` Dmitry Osipenko
2021-11-12 20:26 ` Lyude Paul [this message]
2021-11-12 20:45 ` Dmitry Osipenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=be1833c5d27e666b760c729fc112d1bbd7b7a269.camel@redhat.com \
--to=lyude@redhat.com \
--cc=airlied@linux.ie \
--cc=digetx@gmail.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=jonathanh@nvidia.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tegra@vger.kernel.org \
--cc=maarten.lankhorst@linux.intel.com \
--cc=mripard@kernel.org \
--cc=thierry.reding@gmail.com \
--cc=thomas.graichen@gmail.com \
--cc=tzimmermann@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).