[PATCH] drm/atomic: Convert a warning to dbg atomic printk

[Zack Rusin]

On Tue, 2022-04-05 at 19:09 +0200, Michel Dänzer wrote:
> ⚠ External Email
> 
> On 2022-04-04 20:21, Zack Rusin wrote:
> > From: Zack Rusin <zackr at vmware.com>
> > 
> > By default each flip times out after 0.1 sec
> 
> 10 * HZ is 10 seconds, not 0.1.

Yea, sorry, this entire commit message is not correct. I've sent out a
very old diff with a log the best I could remember. I recall our
conversation now and iirc we said that maybe an interface through drm
atomic code to enable/disable this error is the way to go but after
looking at this again I'm not sure. More below.

> > and a warning about the time out is added to the kernel log. The
> > warning is
> > harmless because there's another flip coming right after but it can
> > quickly fill up
> > the log, e.g. missing 2 flips every second over a 24 hour span will
> > add about 172 thousand lines to the log.
> 
> As we discussed before, while this might be true for the vmwgfx driver,
> for other drivers this message indicates that either the GPU hung, or
> something else went wrong spectacularly. As such, I think we do want to
> see these messages by default for other drivers at least.

I'm not going to argue for or against that but I am curious what's the
point of the message. The message is basically saying "something could
possibly have went very wrong". OK, what's next? Especially if there's
no visible problems and it's not reproducible. Even if it would be
reproducible there's nothing actionable from the message itself. If the
system has no output connected and no users are currently logged in and
we missed a flip, does it matter?

> I suspect this just papers over the real issue even with vmwgfx though.

This goes back to the above. I think you, me and Dave looked at the
logs from those bugs and none of us seem to know what do do about it.
Lacking some other error messages there seems to be nothing this error
adds with vmwgfx or without (we have been adding more logging to vmwgfx
so hopefully with newer kernels we could get some actionable errors but
that's orthogonal to this).

z