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

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Hi,

On 27-12-16 11:58, Jani Nikula wrote:
On Sun, 25 Dec 2016, Hans de Goede <hdegoede@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
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;

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