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

[Jani Nikula <jani.nikula@linux.intel.com>]

On Sun, 25 Dec 2016, Hans de Goede <hdegoede@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?
I.e. do you get "Found valid VBT in ACPI OpRegion (Mailbox #4)\n" in
log? If not, which of the debug messages in intel_bios_is_valid_vbt() do
you get?

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".

BR,
Jani.



>
> Cc: stable@vger.kernel.org
> Signed-off-by: Hans de Goede <hdegoede@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