[Intel-gfx] [PATCH] drm/i915: Hold struct_mutex during hotplug processing

[Andrew Lutomirski]

On Tue, Jul 26, 2011 at 1:54 AM, Keith Packard <keithp at keithp.com> wrote:
> From 59b920597999381fab70c485c161dd50590e561a Mon Sep 17 00:00:00 2001
> From: Keith Packard <keithp at keithp.com>
> Date: Mon, 25 Jul 2011 22:37:51 -0700
> Subject: [PATCH] Revert and fix "drm/i915/dp: remove DPMS mode tracking from
>  DP"
>
> This reverts commit 885a50147f00a8a80108904bf58a18af357717f3.
>
> We actually *do* need to track DPMS state so that on hotplug, we don't
> retrain the link until DPMS is disabled.
>

>        intel_dp->output_reg = output_reg;
> +       intel_dp->dpms_mode = -1;

Should that be some actual mode constant instead of -1?

In any case, this patch, applied manually on top of the struct_mutex
fix, seems to work.  xset dpms force off turns the display off briefly
(presumably X or GNOME helpfully turns it back on), but if I let the
display turn off on its own, it comes back.

There's still an obnoxious bug, though: I use audio over DP, and when
the display turns off, the attached speaker crackles loudly for a
second or two.  I don't think it's a hardware problem with the
monitor, because if I just pull the plug it doesn't make any noise.
Should the driver do something to drop the audio link before turning
off the DP link as a whole?

--Andy