linux-kernel - Re: [PATCH] drm/i915/ddi: Fix default eDP detection on port A

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Date:   Thu, 7 Mar 2019 16:03:45 +0000
From:   Thomas Preston <thomas.preston@...ethink.co.uk>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        airlied@...ux.ie, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915/ddi: Fix default eDP detection on port A

On 07/03/2019 10:34, Jani Nikula wrote:
> There are dangers with default VBTs too. They might contain incorrect
> information about the specific board you have. You'll also have to set
> up the opregion, not just VBT.
> 
> I'm afraid I can't help you there. You already know where to look to see
> how the kernel side expects things to work.
> 
> For testing, the i915.vbt_firmware module parameter is helpful, so you
> don't need to change your BIOS to change the VBT.

Just to clarify, I couldn't get i915.vbt_firmware working with a broken
ACPI OpRegion as intel_opregion_setup() bails out before it reaches
intel_load_vbt_firmware(). I worked around it by moving the fw load but
this isn't a long-term solution.

I need to fix ACPI OpRegion / my BIOS before any of this will work.

diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index 1d946240e55f..128a285a5337 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -971,6 +971,9 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
         BUILD_BUG_ON(sizeof(struct opregion_asle) != 0x100);
         BUILD_BUG_ON(sizeof(struct opregion_asle_ext) != 0x400);

+       if (intel_load_vbt_firmware(dev_priv) == 0)
+               goto out;
+
         pci_read_config_dword(pdev, ASLS, &asls);
         DRM_DEBUG_DRIVER("graphic opregion physical addr: 0x%x\n", asls);
         if (asls == 0) {
@@ -1016,9 +1019,6 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
         if (mboxes & MBOX_ASLE_EXT)
                 DRM_DEBUG_DRIVER("ASLE extension supported\n");

-       if (intel_load_vbt_firmware(dev_priv) == 0)
-               goto out;
-
         if (dmi_check_system(intel_no_opregion_vbt))
                 goto out;