Re: [PATCH v3] driver core: Break infinite loop when deferred probe can't be satisfied

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Marco Felsch <m.felsch@pengutronix.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Grant Likely <grant.likely@arm.com>,
	Saravana Kannan <saravanak@google.com>,
	Andrzej Hajda <a.hajda@samsung.com>,
	artem.bityutskiy@linux.intel.com, Felipe Balbi <balbi@kernel.org>,
	Mark Brown <broonie@kernel.org>, Ferry Toth <fntoth@gmail.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Peter Ujfalusi <peter.ujfalusi@ti.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	kernel-team@android.com, nd <nd@arm.com>,
	Sascha Hauer <kernel@pengutronix.de>
Subject: Re: [PATCH v3] driver core: Break infinite loop when deferred probe can't be satisfied
Date: Mon, 8 Jun 2020 15:11:07 +0300	[thread overview]
Message-ID: <CAHp75VcnkSrb5B8dQE-Tg=mzzUbKZkk3ykm6sxEjNyHWLcF26w@mail.gmail.com> (raw)
In-Reply-To: <20200608115917.f5dhazixnxunl5o5@pengutronix.de>

On Mon, Jun 8, 2020 at 2:59 PM Marco Felsch <m.felsch@pengutronix.de> wrote:
> On 20-06-08 14:13, Andy Shevchenko wrote:
> > On Mon, Jun 8, 2020 at 12:20 PM Marco Felsch <m.felsch@pengutronix.de> wrote:
> > > On 20-03-26 18:31, Andy Shevchenko wrote:

> > > sorry for picking this up again but I stumbled above the same issue
> > > within the driver imx/drm driver which is using the component framework.
> > > I end up in a infinity boot loop if I enabled the HDMI (which is the
> > > DesignWare bridge device) and the LVDS support and the LVDS bind return
> > > with EPROBE_DEFER. There are no words within the component framework docs
> > > which says that this is forbidden. Of course we can work-around the
> > > driver-core framework but IMHO this shouldn't be the way to go. I do not
> > > say that we should revert the commit introducing the regression but we
> > > should address this not only by extending the docs since the most
> > > drm-drivers are using the component framework and can end up in the same
> > > situation.
> > >
> > > > > It can be solved by refactoring the driver probe routine. If a resource is
> > > > > required to be present, then check that it is available early; before
> > > > > registering child devices.
> > > >
> > > > We fix one and leave others.
> > >
> > > E.g. the imx-drm and the sunxi driver...
> >
> > Just out of curiosity, does my patch fix an issue for you?
>
> I didn't applied your patch yet. I can test it if you want.

If you can, thanks!

> > > > > The proposed solution to modify driver core is fragile and susceptible to
> > > > > side effects from other probe paths. I don't think it is the right approach.

-- 
With Best Regards,
Andy Shevchenko