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

[Jani Nikula]

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.

I'm sorry. Going through the opregion specs is not something I cherish,
so I've been postponing this... I'll try to check later today.

BR,
Jani.

>
> Regards,
>
> Hans
>
>
>
>>>> Cc: stable at vger.kernel.org
>>>> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
>>>> ---
>>>> Note even with this fixed the panel still does not work with 4.9,
>>>> but it does with drm-intel-next-queued :) I believe the missing bit in
>>>> 4.9 is the "drm/915: Parsing the missed out DTD fields from the VBT"
>>>> commit, but I've not verified this.
>>>> ---
>>>>  drivers/gpu/drm/i915/intel_opregion.c | 4 +++-
>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
>>>> index f4429f6..eff35ae 100644
>>>> --- a/drivers/gpu/drm/i915/intel_opregion.c
>>>> +++ b/drivers/gpu/drm/i915/intel_opregion.c
>>>> @@ -982,7 +982,9 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
>>>>              opregion->vbt_size = vbt_size;
>>>>          } else {
>>>>              vbt = base + OPREGION_VBT_OFFSET;
>>>> -            vbt_size = OPREGION_ASLE_EXT_OFFSET - OPREGION_VBT_OFFSET;
>>>> +            vbt_size = (mboxes & MBOX_ASLE_EXT) ?
>>>> +                OPREGION_ASLE_EXT_OFFSET : OPREGION_SIZE;
>>>> +            vbt_size -= OPREGION_VBT_OFFSET;
>>>>              if (intel_bios_is_valid_vbt(vbt, vbt_size)) {
>>>>                  DRM_DEBUG_KMS("Found valid VBT in ACPI OpRegion (Mailbox #4)\n");
>>>>                  opregion->vbt = vbt;
>>>

-- 
Jani Nikula, Intel Open Source Technology Center