From: Daniel Vetter <daniel@ffwll.ch>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>, Feng Tang <feng.tang@intel.com>,
intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/dp: add module parameter for the dpcd access max retries
Date: Mon, 7 May 2018 17:09:21 +0200 [thread overview]
Message-ID: <20180507150921.GC28661@phenom.ffwll.local> (raw)
In-Reply-To: <152570000533.9723.9317373149400371902@mail.alporthouse.com>
On Mon, May 07, 2018 at 02:33:25PM +0100, Chris Wilson wrote:
> Quoting Feng Tang (2018-05-07 22:26:34)
> > Hi Chris,
> >
> > Thanks for the prompt review!
> >
> > On Mon, May 07, 2018 at 11:40:45AM +0100, Chris Wilson wrote:
> > > Quoting Feng Tang (2018-05-07 11:36:09)
> > > > To fulfil the Dell 4K monitor, the dpcd max retries has been bumped
> > > > from 7 to 32, which may hurt the boot/init time for some platforms,
> > > > as the 32 retries may take hundreds of ms.
> > >
> > > If we need that many retries, so be it. No modparam, the driver just has
> > > to work.
> >
> > I understand your point. The retry numer was originally 7, and worked
> > fine untill the Dell 4K monitor which changes to 32. According to my test,
> > each retry will take about 8ms on the A3960 based NUC.
> >
> > One of our product need to boot up within a given time limit, this
> > 32 retries will take about 1/3 of the budget (about 270ms), that's
> > why I would try to make it a parameter.
>
> The essence is that probing whether a monitor is connected should not be
> blocking boot. If an async probe tries and fails to find a monitor,
> fine - no one will notice. If it does take 270ms to find a monitor, it
> turns on 200ms after userspace kicks in, just like any other hotplug.
Yeah, the fix here is to get the probing out of the driver load path, not
to break the driver for some funky monitors. And definitely not using a
modparam.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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next prev parent reply other threads:[~2018-05-07 15:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-07 10:36 [PATCH] drm/dp: add module parameter for the dpcd access max retries Feng Tang
2018-05-07 10:40 ` Chris Wilson
2018-05-07 21:26 ` Feng Tang
2018-05-07 13:33 ` Chris Wilson
2018-05-07 15:09 ` Daniel Vetter [this message]
2018-05-07 23:19 ` Feng Tang
2018-05-08 19:03 ` Feng Tang
2018-05-08 11:33 ` [Intel-gfx] " Chris Wilson
2018-05-08 12:00 ` Daniel Vetter
2018-05-08 23:08 ` [Intel-gfx] " Feng Tang
2018-05-08 19:30 ` Jani Nikula
2018-05-09 6:31 ` Feng Tang
2018-05-09 7:53 ` Jani Nikula
2018-05-09 7:56 ` Feng Tang
2018-05-09 9:28 ` [Intel-gfx] " Jani Nikula
2018-05-10 9:21 ` Feng Tang
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