[Intel-gfx] [PATCH 0/2] drm: link status property and DP link training failure handling

[Martin Peres]

On 20/01/17 18:44, Jani Nikula wrote:
> On Fri, 20 Jan 2017, Martin Peres <martin.peres at linux.intel.com> wrote:
>> On 19/01/17 11:18, Jani Nikula wrote:
>>> On Wed, 18 Jan 2017, Martin Peres <martin.peres at linux.intel.com> wrote:
>>>> On 16/12/16 15:48, Daniel Vetter wrote:
>>>>> On Fri, Dec 16, 2016 at 12:29:05PM +0200, Jani Nikula wrote:
>>>>>> The two remaining patches from [1], rebased.
>>>>>>
>>>>>> BR,
>>>>>> Jani.
>>>>>>
>>>>>>
>>>>>> [1] http://mid.mail-archive.com/1480984058-552-1-git-send-email-manasi.d.navare@intel.com
>>>>>
>>>>> Just for the record, I think the only thing missing here is the Xorg
>>>>> review on the -modesetting patch. As soon as we have that I can vacuum
>>>>> this up (probably best through drm-misc, but not sure).
>>>>
>>>> Hey Daniel,
>>>>
>>>> I tested again on Monday -modesetting with the patch from Jani to inject
>>>> faults and did manage to get both the link-status BAD and a lower
>>>> resolution got select dynamically when running KDE. For the latter, I
>>>> however needed the following patch:
>>>> https://patchwork.kernel.org/patch/9491869/
>>>>
>>>> Now, that being said, Jani's patch just prevents a new modeset to work,
>>>> it does not tear down the current mode. This may be the reason why I do
>>>> not manage to get a black screen after > 3 failures (and already a
>>>> 1024x768 resolution).
>>>>
>>>> I however need to do more testing when running without a DE (straight X
>>>> + twm and xterm). Indeed, when I hotplug my DP screen, it gets to the
>>>> native resolution automatically without me asking for it using xrandr.
>>>> Also, the mode that is set does not seem to go through
>>>> intel_dp_start_link_train (what the heck?), so I do not get any failure
>>>> and I cannot induce one :s
>>>
>>> Huh, does your X + twm actually respond to hotplugs?
>>>
>>
>> No, that was the point of the test :) I just wanted to see the screen
>> turn black but it did not because even if the link training fails, i915
>> keeps on going and pushes the pixels out constantly. My screen was
>> good-enough to pick it up and display it without complaining ... which
>> is really surprising for DP, isn't it?
>
> And this, my friend, is why we plunge on in spite of errors, instead of
> failing fast and bailing out. If you were a normal user, you'd
> *appreciate* not having a black screen! ;)

I definitely would *love* this approach. Just was confusing ;) Thanks a 
lot for yesterday's discussion!