drm/i915/pch: Save/restore PCH_PORT_HOTPLUG across suspend
At least on a Lenovo X220 the HPD bits of this are enabled at boot but
cleared after resume, which means plug interrupts stop working.
This also happens to fix DP displays re-lighting on resume. I'm quite
certain that's an accident: the first DP link train inevitably fails on
that machine, and it's only serendipity that we're getting multiple plug
interrupts and the second train works. But I shall take my victories
where I get them.
Signed-off-by: Adam Jackson <ajax@redhat.com> Tested-by: Keith Packard <keithp@keithp.com> Reviewed-by: Keith Packard <keithp@keithp.com> Signed-off-by: Keith Packard <keithp@keithp.com>
projects / ~andy / linux / commit