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drm/i915: Addin-offset is an unreliable indicator of LVDS presence (v2)

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My Samsung N210 has a VBT with DEVICE_TYPE_INT_LFP with a zero
addin-offset. With the check in place, the panel was declared absent.

v2: Only trust BIOS writers that have graduated to writing OpRegions.
(We are all doomed.)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zhao Yakui <yakui.zhao@intel.com>
Cc: Adam Jackson <ajax@redhat.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
This commit is contained in:
Chris Wilson
2010-08-22 18:21:42 +01:00
parent 44834a67c0
commit 425904dd8a
1 changed files with 26 additions and 20 deletions
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46
drivers/gpu/drm/i915/intel_lvds.c
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@@ -777,38 +777,44 @@ static void intel_find_lvds_downclock(struct drm_device *dev,
* If it is present, return 1. * If it is present, return 1.
* If it is not present, return false. * If it is not present, return false.
* If no child dev is parsed from VBT, it assumes that the LVDS is present. * If no child dev is parsed from VBT, it assumes that the LVDS is present.
* Note: The addin_offset should also be checked for LVDS panel.
* Only when it is non-zero, it is assumed that it is present.
*/ */
static int lvds_is_present_in_vbt(struct drm_device *dev) static bool lvds_is_present_in_vbt(struct drm_device *dev)
{ {
struct drm_i915_private *dev_priv = dev->dev_private; struct drm_i915_private *dev_priv = dev->dev_private;
struct child_device_config *p_child; int i;
int i, ret;
if (!dev_priv->child_dev_num) if (!dev_priv->child_dev_num)
return 1; return true;
ret = 0;
for (i = 0; i < dev_priv->child_dev_num; i++) { for (i = 0; i < dev_priv->child_dev_num; i++) {
p_child = dev_priv->child_dev + i; struct child_device_config *child = dev_priv->child_dev + i;
/*
* If the device type is not LFP, continue. /* If the device type is not LFP, continue.
* If the device type is 0x22, it is also regarded as LFP. * We have to check both the new identifiers as well as the
* old for compatibility with some BIOSes.
*/ */
if (p_child->device_type != DEVICE_TYPE_INT_LFP && if (child->device_type != DEVICE_TYPE_INT_LFP &&
p_child->device_type != DEVICE_TYPE_LFP) child->device_type != DEVICE_TYPE_LFP)
continue; continue;
/* The addin_offset should be checked. Only when it is /* However, we cannot trust the BIOS writers to populate
* non-zero, it is regarded as present. * the VBT correctly. Since LVDS requires additional
* information from AIM blocks, a non-zero addin offset is
* a good indicator that the LVDS is actually present.
*/ */
if (p_child->addin_offset) { if (child->addin_offset)
ret = 1; return true;
break;
/* But even then some BIOS writers perform some black magic
* and instantiate the device without reference to any
* additional data. Trust that if the VBT was written into
* the OpRegion then they have validated the LVDS's existence.
*/
if (dev_priv->opregion.vbt)
return true;
} }
}
return ret; return false;
} }
/** /**