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

[Hans de Goede]

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 ?

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;
>