[Intel-gfx] debugging Haswell eDP black screen after S3

[Ben Guthro]

On Thu, May 16, 2013 at 9:24 AM, Ben Guthro <ben at guthro.net> wrote:
> On Wed, May 15, 2013 at 4:42 PM, Ben Guthro <ben at guthro.net> wrote:
>> On Tue, May 14, 2013 at 5:01 PM, Ben Guthro <ben at guthro.net> wrote:
>>> I am attempting to debug an issue with some Haswell laptop systems
>>> which do not restore their screen after resuming from S3 when running
>>> on the stable 3.8 kernel (3.8.13)
>>> The backlight is OK, but the screen is just black.
>>>
>>> In trying to determine what was going wrong, I tried looking at the
>>> output of intel_reg_dumper, in a good, and bad case:
>>>
>>> diff -u good_reg.txt bad_reg.txt
>>> --- good_reg.txt        2013-05-14 15:08:44.361997000 +0000
>>> +++ bad_reg.txt 2013-05-14 15:09:20.480000000 +0000
>>> @@ -1,5 +1,4 @@
>>> -                 DCC: 0x00000000 (0x00000000f3400000
>>> 0x00000000f37fffff 0x00000000��
>>> -� )
>>> +                 DCC: 0x00000000 (0x00000000f3400000
>>> 0x00000000f37fffff 0x00000000��= � )
>>>             CHDECMISC: 0x00000000 (none, ch2 enh disabled, ch1 enh
>>> disabled, ch0 enh disabled, flex disabled, ep not present)
>>>                C0DRB0: 0x00000000 (0x0000)
>>>                C0DRB1: 0x00000000 (0x0000)
>>> @@ -63,17 +62,17 @@
>>>       PIPEA_DP_LINK_N: 0x00000000
>>>         CURSOR_A_BASE: 0x01061000
>>>      CURSOR_A_CONTROL: 0x04000027
>>> -   CURSOR_A_POSITION: 0x03a3032f
>>> +   CURSOR_A_POSITION: 0x01bb03fb
>>>                  FPA0: 0x00000000 (n = 0, m1 = 0, m2 = 0)
>>>                  FPA1: 0x00000000 (n = 0, m1 = 0, m2 = 0)
>>>                DPLL_A: 0x00000000 (disabled, non-dvo, VGA, default
>>> clock, unknown mode, p1 = 0, p2 = 0)
>>>             DPLL_A_MD: 0x00000000
>>> -            HTOTAL_A: 0x0821077f (1920 active, 2082 total)
>>> -            HBLANK_A: 0x0821077f (1920 start, 2082 end)
>>> -             HSYNC_A: 0x081307af (1968 start, 2068 end)
>>> -            VTOTAL_A: 0x045f0437 (1080 active, 1120 total)
>>> -            VBLANK_A: 0x045f0437 (1080 start, 1120 end)
>>> -             VSYNC_A: 0x044b0441 (1090 start, 1100 end)
>>> +            HTOTAL_A: 0x00000000 (1 active, 1 total)
>>> +            HBLANK_A: 0x00000000 (1 start, 1 end)
>>> +             HSYNC_A: 0x00000000 (1 start, 1 end)
>>> +            VTOTAL_A: 0x00000000 (1 active, 1 total)
>>> +            VBLANK_A: 0x00000000 (1 start, 1 end)
>>> +             VSYNC_A: 0x00000000 (1 start, 1 end)
>>>             BCLRPAT_A: 0x00000000
>>>          VSYNCSHIFT_A: 0x00000000
>>>              DSPBCNTR: 0x00004000 (disabled, pipe A)
>>>
>>>
>>> It appears the registers that are saved, and restored in
>>> i915_save_modeset_reg / i915_restore_modeset_reg is not working
>>> properly.
>>>
>>> When I put some debug in, I discovered that it was bailing out of
>>> i915_save_modeset_reg early since the DRIVER_MODESET bit was cleared.
>>> However, it was set at the end of i915_init()
>>> This, of course, confuses me.
>>>
>>> Am I seeing memory corruption here?
>>
>> It looks like I misread the code here, inversing an if statement state.
>>
>> That said, I don't really have any clues as to why the display is
>> black after resuming from S3

It appears that S3 is not necessary.

I can reproduce the black screen with just vbetool:
vbetool dpms off
vbetool dpms on

Does this suggest a bios issue?



>>
>> Is this an eDP training issue? Are there any changesets I can try backporting?
>> I tried this, but it didn't seem to help:
>> https://patchwork.kernel.org/patch/2516601/
>
>
> Below is a serial dump with drm.debug=4, after resuming from S3
>
> If anyone sees anything awry, being pointed in the right direction
> would be appreciated: