[Intel-gfx] [PATCH] drm/i915: Fix not finding the VBT when it overlaps with OPREGION_ASLE_EXT

[Hans de Goede]

Hi,

On 23-01-17 11:36, Jani Nikula wrote:
> On Fri, 20 Jan 2017, Hans de Goede <hdegoede at redhat.com> wrote:
>> Hi,
>>
>> On 31-12-16 17:00, Hans de Goede wrote:
>>> Hi,
>>>
>>> On 27-12-16 11:58, Jani Nikula wrote:
>>>> On Sun, 25 Dec 2016, Hans de Goede <hdegoede at redhat.com> wrote:
>>>>> If there is no OPREGION_ASLE_EXT then a VBT stored in mailbox #4 may
>>>>> use the ASLE_EXT parts of the opregion. Adjust the vbt_size calculation
>>>>> for a vbt in mailbox #4 for this.
>>>>>
>>>>> This fixes the driver not finding the VBT on a jumper ezpad mini3
>>>>> cherrytrail tablet.
>>>>
>>>> Thanks for the patch. I think you're onto something, but I don't think
>>>> the patch is quite correct. That said, I'm not sure myself yet what
>>>> would be. ;)
>>>>
>>>> Without the change, does intel_bios_is_valid_vbt() return true anyway?
>>>
>>> No.
>>>
>>>> I.e. do you get "Found valid VBT in ACPI OpRegion (Mailbox #4)\n" in
>>>> log?
>>>
>>> No.
>>>
>>>> If not, which of the debug messages in intel_bios_is_valid_vbt() do
>>>> you get?
>>>
>>> I get "BDB incomplete", which is why I wrote this patch and believe
>>> this patch is the right solution. With this patch everything works,
>>>
>>>> In the latter case, I suspect you'll end up with failure in intel_bios.c
>>>> with either "No MIPI config BDB found" or "No MIPI Sequence found,
>>>> parsing complete\n".
>>>
>>> I don't remember the exact error, other then getting the
>>> "BDB incomplete" error, and the i915 driver not listing the DSI connector
>>> under /sys/class drm.
>>>
>>> What makes you say: "but I don't think the patch is quite correct" why
>>> should the code still keep the OPREGION_ASLE_EXT start as end of the
>>> mailbox #4 vbt if there is the ASLE extenstion is not used ?
>>
>> Ping, any progress on this ? I still believe my original patch is
>> correct. Eitherway I would like to see a fix for this, be it this fix
>> or something else, as a fix is necessary to get the LCD panel to work
>> on jumper ezpad mini3 tablets.
>
> Please send me /sys/kernel/debug/dri/0/i915_opregion on that machine.
>
> Perusing the opregion spec (which I regret I can't share with you), I
> found this:
>
> * On mailboxes in general, "Mail-box locations are fixed and should
>   always be allocated irrespective of the support for a given mail box
>   is available or not."
>
> * On opregion->asle->rvda, "This is mainly used when VBT size exceeds
>   6KB and can't be stored in Mailbox4." It isn't clear to me whether
>   ->rvda was used or not. The opregion dump should shed light on
>   this. You can of course check that by adding debug prints in the code
>   too.
>
> * On mailbox 4 (the VBT), "Holds a maximum of 6KB sized Raw VBT data
>   (not VBIOS image) from VBIOS image."
>
> Clearly the patch is against the spec. Let's see if the opregion you
> have there is against the spec too, and proceed from there...

Ok, I've attached a dump of the opregion on the tablet in question.

Regards,

Hans

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