[Intel-gfx] PROBLEM: i915 Haswell KMS wrong maximum resolution

[Bruno Prémont]

Hi Kenneth,

On Fri, 28 March 2014 Kenneth de Mello <kdemello1980 at gmail.com> wrote:
> On my system, the maximum resolution of my monitor, 2560x1440, is no longer
> automatically detected properly with kernel 3.13.7.   This worked with
> 3.13.6, and 5 with this hardware and identical kernel configs.    Now the
> autodetected resolution is 1920x1080.
> 
> The monitor is plugged into the DVI port on my motherboard.
> 
> My system:
> 
> - i7-4770 (non-K) CPU
> - asrock z87 extreme6 motherboard
> - Dell U2711 monitor
> 
> The integrated graphics adapter is configured as the primary in the BIOS,
> and the discreet card is passed through to a Xen guest.   Kernel 3.13.7
> mis-detects the resolution regardless if it is being booted with Xen or
> without it (and previous versions worked as expected).  More detailed
> system information is attached.
> 
> I don't notice any unusual messages, other than the wrong resolution.
> 
> Steps to reproduce:  Boot with kernel 3.13.7 (with or without Xen)
> 
> I'd be happy to provide more detail if required.

This smells like the following change in 3.13.6 to 3.13.7 might
be the cause:

commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2
Author: Ville Syrjälä <ville.syrjala at linux.intel.com>
Date:   Mon Mar 3 11:33:36 2014 +0200

    drm/i915: Reject >165MHz modes w/ DVI monitors

    commit 6375b768a9850b6154478993e5fb566fa4614a9c upstream.

    Single-link DVI max dotclock is 165MHz. Filter out modes with higher
    dotclock when the monitor doesn't support HDMI.

    Modes higher than 165 MHz were allowed in

    commit 7d148ef51a657fd04036c3ed7803da600dd0d451
    Author: Daniel Vetter <daniel.vetter at ffwll.ch>
    Date:   Mon Jul 22 18:02:39 2013 +0200

        drm/i915: fix hdmi portclock limits

    Also don't attempt to use 12bpc mode with DVI monitors.

    Cc: Adam Nielsen <a.nielsen at shikadi.net>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75345
    Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=70331
    Tested-by: Ralf Jung <post+kernel at ralfj.de>
    Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
    Signed-off-by: Jani Nikula <jani.nikula at intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>


Bruno