i915 DVI resolution regression (3.13.7+)

i915 DVI resolution regression (3.13.7+)

[Daniel J Blueman]

Ville et al,

It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
another commit in 3.13.7) broke modes which require DVI-D dual-link,
eg 2560x1440 with my panel.

I don't see these modelines in 3.13.7 or later (eg 3.14):

[     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
[     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
[     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)

My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.

Thanks,
  Daniel
-- 
Daniel J Blueman

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Jani Nikula]

On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
> Ville et al,
>
> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
> another commit in 3.13.7) broke modes which require DVI-D dual-link,
> eg 2560x1440 with my panel.
>
> I don't see these modelines in 3.13.7 or later (eg 3.14):
>
> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>
> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.

By allowing those modes we regressed setups which were not capable of
displaying them. So you've got an HDMI->DVI converter?

https://bugzilla.kernel.org/show_bug.cgi?id=72961


-- 
Jani Nikula, Intel Open Source Technology Center

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Daniel J Blueman]

On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
>> Ville et al,
>>
>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
>> eg 2560x1440 with my panel.
>>
>> I don't see these modelines in 3.13.7 or later (eg 3.14):
>>
>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>>
>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
>
> By allowing those modes we regressed setups which were not capable of
> displaying them. So you've got an HDMI->DVI converter?
>
> https://bugzilla.kernel.org/show_bug.cgi?id=72961

I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
previously couldn't get 2560x1440 via HDMI.

If it isn't this commit, then it may be another commit in 3.13.7,
albeit it feels less likely.

Thanks,
  Daniel
-- 
Daniel J Blueman

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Daniel Vetter]

On Tue, Apr 8, 2014 at 9:32 AM, Daniel J Blueman <daniel@quora.org> wrote:
> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
> previously couldn't get 2560x1440 via HDMI.
>
> If it isn't this commit, then it may be another commit in 3.13.7,
> albeit it feels less likely.

Before we go on a wild goose chase, can you please confirm your
suspicion with a revert?

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Daniel J Blueman]

Ville et al,

On 8 April 2014 16:02, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> On Tue, Apr 8, 2014 at 9:32 AM, Daniel J Blueman <daniel@quora.org> wrote:
>> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
>> previously couldn't get 2560x1440 via HDMI.
>>
>> If it isn't this commit, then it may be another commit in 3.13.7,
>> albeit it feels less likely.
>
> Before we go on a wild goose chase, can you please confirm your
> suspicion with a revert?

I built stock 3.13.7 to reproduce the issue (Ubuntu mainline config);
I reverted e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 and rebuilt, and
don't see the issue. It's probably an idea if you have a panel that
requires dual-link DVI on the automated test matrix if not already.

Anyway, glad to have helped.

Thanks,
  Daniel
-- 
Daniel J Blueman

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Dave Airlie]

On Tue, Apr 8, 2014 at 5:32 PM, Daniel J Blueman <daniel@quora.org> wrote:
> On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
>>> Ville et al,
>>>
>>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
>>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
>>> eg 2560x1440 with my panel.
>>>
>>> I don't see these modelines in 3.13.7 or later (eg 3.14):
>>>
>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
>>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>>>
>>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
>>
>> By allowing those modes we regressed setups which were not capable of
>> displaying them. So you've got an HDMI->DVI converter?
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=72961
>
> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
> previously couldn't get 2560x1440 via HDMI.

Intel hw has dual-link DVI-D? I'm not sure I've ever seen that, is
this SDVO device or plain DVI-D?

Dave.

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Daniel J Blueman]

On 9 April 2014 11:41, Dave Airlie <airlied@gmail.com> wrote:
> On Tue, Apr 8, 2014 at 5:32 PM, Daniel J Blueman <daniel@quora.org> wrote:
>> On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>>> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
>>>> Ville et al,
>>>>
>>>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
>>>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
>>>> eg 2560x1440 with my panel.
>>>>
>>>> I don't see these modelines in 3.13.7 or later (eg 3.14):
>>>>
>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
>>>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>>>>
>>>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
>>>
>>> By allowing those modes we regressed setups which were not capable of
>>> displaying them. So you've got an HDMI->DVI converter?
>>>
>>> https://bugzilla.kernel.org/show_bug.cgi?id=72961
>>
>> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
>> previously couldn't get 2560x1440 via HDMI.
>
> Intel hw has dual-link DVI-D? I'm not sure I've ever seen that, is
> this SDVO device or plain DVI-D?

It's the DVI-D connector on: https://www.asus.com/Motherboards/H87IPLUS/

However, it is logically detected as HDMI-0:

$ xrandr
Screen 0: minimum 320 x 320, current 2560 x 1440, maximum 32767 x 32767
VGA-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected primary 2560x1440+0+0 (normal left inverted right x
axis y axis) 600mm x 340mm
   2560x1440      60.0*+
   1920x1200      59.9
   1920x1080      60.0
   1600x1200      59.9
   1680x1050      59.9
   1280x1024      74.9     59.9
   1280x800       59.8
   1152x864       74.8
   1024x768       74.9     59.9
   800x600        74.9     60.3
   640x480        74.8     59.4
   720x400        69.8
HDMI-1 disconnected (normal left inverted right x axis y axis)

Using the mobo HDMI socket and a HDMI to dual-link DVI-D cable
(logically detected as HDMI-1), the same patch causes the same issue.

Thanks,
  Daniel
-- 
Daniel J Blueman

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Dave Airlie]

On Wed, Apr 9, 2014 at 4:07 PM, Daniel J Blueman <daniel@quora.org> wrote:
> On 9 April 2014 11:41, Dave Airlie <airlied@gmail.com> wrote:
>> On Tue, Apr 8, 2014 at 5:32 PM, Daniel J Blueman <daniel@quora.org> wrote:
>>> On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>>>> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
>>>>> Ville et al,
>>>>>
>>>>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
>>>>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
>>>>> eg 2560x1440 with my panel.
>>>>>
>>>>> I don't see these modelines in 3.13.7 or later (eg 3.14):
>>>>>
>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
>>>>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>>>>>
>>>>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
>>>>
>>>> By allowing those modes we regressed setups which were not capable of
>>>> displaying them. So you've got an HDMI->DVI converter?
>>>>
>>>> https://bugzilla.kernel.org/show_bug.cgi?id=72961
>>>
>>> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
>>> previously couldn't get 2560x1440 via HDMI.
>>
>> Intel hw has dual-link DVI-D? I'm not sure I've ever seen that, is
>> this SDVO device or plain DVI-D?
>
> It's the DVI-D connector on: https://www.asus.com/Motherboards/H87IPLUS/

The link which says "

Integrated Graphics Processor
- Supports HDMI with max. resolution 4096 x 2304 @ 24 Hz
- Supports DVI with max. resolution 1920 x 1200 @ 60 Hz
- Supports RGB with max. resolution 1920 x 1200 @ 60 Hz

I'm even wondering electrically how a HDMI->dual-link DVI adapter works.

Dave.

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Jani Nikula]

On Wed, 09 Apr 2014, Dave Airlie <airlied@gmail.com> wrote:
> On Wed, Apr 9, 2014 at 4:07 PM, Daniel J Blueman <daniel@quora.org> wrote:
>> On 9 April 2014 11:41, Dave Airlie <airlied@gmail.com> wrote:
>>> On Tue, Apr 8, 2014 at 5:32 PM, Daniel J Blueman <daniel@quora.org> wrote:
>>>> On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>>>>> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
>>>>>> Ville et al,
>>>>>>
>>>>>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
>>>>>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
>>>>>> eg 2560x1440 with my panel.
>>>>>>
>>>>>> I don't see these modelines in 3.13.7 or later (eg 3.14):
>>>>>>
>>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>>>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
>>>>>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>>>>>>
>>>>>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
>>>>>
>>>>> By allowing those modes we regressed setups which were not capable of
>>>>> displaying them. So you've got an HDMI->DVI converter?
>>>>>
>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=72961
>>>>
>>>> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
>>>> previously couldn't get 2560x1440 via HDMI.
>>>
>>> Intel hw has dual-link DVI-D? I'm not sure I've ever seen that, is
>>> this SDVO device or plain DVI-D?
>>
>> It's the DVI-D connector on: https://www.asus.com/Motherboards/H87IPLUS/
>
> The link which says "
>
> Integrated Graphics Processor
> - Supports HDMI with max. resolution 4096 x 2304 @ 24 Hz
> - Supports DVI with max. resolution 1920 x 1200 @ 60 Hz
> - Supports RGB with max. resolution 1920 x 1200 @ 60 Hz
>
> I'm even wondering electrically how a HDMI->dual-link DVI adapter works.

The current assumption is that in the working case, they are really
operated in single-link, with a frequency beyond the single-link DVI
cable spec.

BR,
Jani.



>
> Dave.

-- 
Jani Nikula, Intel Open Source Technology Center

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Daniel J Blueman]

On 9 April 2014 15:08, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Wed, 09 Apr 2014, Dave Airlie <airlied@gmail.com> wrote:
>> On Wed, Apr 9, 2014 at 4:07 PM, Daniel J Blueman <daniel@quora.org> wrote:
>>> On 9 April 2014 11:41, Dave Airlie <airlied@gmail.com> wrote:
>>>> On Tue, Apr 8, 2014 at 5:32 PM, Daniel J Blueman <daniel@quora.org> wrote:
>>>>> On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>>>>>> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
>>>>>>> Ville et al,
>>>>>>>
>>>>>>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
>>>>>>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
>>>>>>> eg 2560x1440 with my panel.
>>>>>>>
>>>>>>> I don't see these modelines in 3.13.7 or later (eg 3.14):
>>>>>>>
>>>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
>>>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
>>>>>>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
>>>>>>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
>>>>>>>
>>>>>>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
>>>>>>
>>>>>> By allowing those modes we regressed setups which were not capable of
>>>>>> displaying them. So you've got an HDMI->DVI converter?
>>>>>>
>>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=72961
>>>>>
>>>>> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
>>>>> previously couldn't get 2560x1440 via HDMI.
>>>>
>>>> Intel hw has dual-link DVI-D? I'm not sure I've ever seen that, is
>>>> this SDVO device or plain DVI-D?
>>>
>>> It's the DVI-D connector on: https://www.asus.com/Motherboards/H87IPLUS/
>>
>> The link which says "
>>
>> Integrated Graphics Processor
>> - Supports HDMI with max. resolution 4096 x 2304 @ 24 Hz
>> - Supports DVI with max. resolution 1920 x 1200 @ 60 Hz
>> - Supports RGB with max. resolution 1920 x 1200 @ 60 Hz
>>
>> I'm even wondering electrically how a HDMI->dual-link DVI adapter works.
>
> The current assumption is that in the working case, they are really
> operated in single-link, with a frequency beyond the single-link DVI
> cable spec.

I checked with a single link DVI-D cable, and see the same behaviour
as with a dual link cable. This would have had to be driven out of
spec to achieve the resolution and refresh rate of my panel. That
said, the spec is old and the shielding on the dual-link cable
supplied with the panel is way over-specced.

If Intel GPUs (such as my Haswell board here) don't support dual-link
DVI, then this patch will prevent using panels >1920x1200 unless they
advertise low-refresh rate modes. It looks like the panel
manufacturers assume dual-link will be available.

The lesser of the evils may be to allow reasonable out-of-spec
dotclocks, unless I'm missing something?
-- 
Daniel J Blueman

Re: [Intel-gfx] i915 DVI resolution regression (3.13.7+)

[Ville Syrjälä]

On Tue, Apr 15, 2014 at 02:27:41PM +0800, Daniel J Blueman wrote:
> On 9 April 2014 15:08, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> > On Wed, 09 Apr 2014, Dave Airlie <airlied@gmail.com> wrote:
> >> On Wed, Apr 9, 2014 at 4:07 PM, Daniel J Blueman <daniel@quora.org> wrote:
> >>> On 9 April 2014 11:41, Dave Airlie <airlied@gmail.com> wrote:
> >>>> On Tue, Apr 8, 2014 at 5:32 PM, Daniel J Blueman <daniel@quora.org> wrote:
> >>>>> On 8 April 2014 15:14, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> >>>>>> On Tue, 08 Apr 2014, Daniel J Blueman <daniel@quora.org> wrote:
> >>>>>>> Ville et al,
> >>>>>>>
> >>>>>>> It looks like commit e3ea8fa6beaf55fee64bf816f3b8a80ad733b2c2 (or
> >>>>>>> another commit in 3.13.7) broke modes which require DVI-D dual-link,
> >>>>>>> eg 2560x1440 with my panel.
> >>>>>>>
> >>>>>>> I don't see these modelines in 3.13.7 or later (eg 3.14):
> >>>>>>>
> >>>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
> >>>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
> >>>>>>> [     5.582] (II) intel(0): Modeline "2560x1440"x60.0  312.25  2560
> >>>>>>> 2752 3024 3488  1440 1443 1448 1493 -hsync +vsync (89.5 kHz eP)
> >>>>>>> [     5.582] (II) intel(0): Modeline "1920x1200"x59.9  193.25  1920
> >>>>>>> 2056 2256 2592  1200 1203 1209 1245 -hsync +vsync (74.6 kHz e)
> >>>>>>>
> >>>>>>> My monitor is a Dell U2713HM; mobo uses an H87 chipset with i5-4670.
> >>>>>>
> >>>>>> By allowing those modes we regressed setups which were not capable of
> >>>>>> displaying them. So you've got an HDMI->DVI converter?
> >>>>>>
> >>>>>> https://bugzilla.kernel.org/show_bug.cgi?id=72961
> >>>>>
> >>>>> I am using a dual-link DVI-D to DVI-D cable to this monitor, since I
> >>>>> previously couldn't get 2560x1440 via HDMI.
> >>>>
> >>>> Intel hw has dual-link DVI-D? I'm not sure I've ever seen that, is
> >>>> this SDVO device or plain DVI-D?
> >>>
> >>> It's the DVI-D connector on: https://www.asus.com/Motherboards/H87IPLUS/
> >>
> >> The link which says "
> >>
> >> Integrated Graphics Processor
> >> - Supports HDMI with max. resolution 4096 x 2304 @ 24 Hz
> >> - Supports DVI with max. resolution 1920 x 1200 @ 60 Hz
> >> - Supports RGB with max. resolution 1920 x 1200 @ 60 Hz
> >>
> >> I'm even wondering electrically how a HDMI->dual-link DVI adapter works.
> >
> > The current assumption is that in the working case, they are really
> > operated in single-link, with a frequency beyond the single-link DVI
> > cable spec.
> 
> I checked with a single link DVI-D cable, and see the same behaviour
> as with a dual link cable. This would have had to be driven out of
> spec to achieve the resolution and refresh rate of my panel. That
> said, the spec is old and the shielding on the dual-link cable
> supplied with the panel is way over-specced.
> 
> If Intel GPUs (such as my Haswell board here) don't support dual-link
> DVI, then this patch will prevent using panels >1920x1200 unless they
> advertise low-refresh rate modes. It looks like the panel
> manufacturers assume dual-link will be available.

I don't think I've ever seen a display that would _require_ dual-link.
You should at least get some kind of picture with single-link.

> 
> The lesser of the evils may be to allow reasonable out-of-spec
> dotclocks, unless I'm missing something?

No, we can't do that. If the display won't accept the out of spec
signal you get no picture. If the display will accept higher
frequencies it needs to tell us that by including the HDMI VSDB
in the EDID. There's no other way for us to know.

What we do now is allow the user to specify a mode manually that's out
of spec, but we won't include such modes in the list automatically. That
should guarantee that everyone gets some kind of picture on the screen
off the bat, while still allowing the user to force any mode he wishes.

-- 
Ville Syrjälä
Intel OTC