[PATCH] drm/i915: Quirk to ignore VBT bpp

[Ben Widawsky <benjamin.widawsky@intel.com>]

We've had several reports of an Asus Zenbook reporting an 18bpp eDP
display, which then proceeds to not work. Using the default 24, work
just fine. Since it appears this is somewhat common in the budding world
of eDP, make a new quirk for it, and use it.

This code has been changed several times. Amongst the most recent with
the best history are:

commit 57c219633275c7e7413f8bc7be250dc092887458
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Thu Apr 4 17:19:37 2013 +0200

    drm/i915: revert eDP bpp clamping code changes

and

commit af13188a1a6623fc8b4b6c42178046fb80f8b1d0
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Tue Feb 19 17:45:00 2013 +0100

    drm/i915: force bpp for eDP panels

Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
CC: Adam Jackson <ajax@redhat.com>
CC: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
---
 drivers/gpu/drm/i915/i915_drv.h      |  1 +
 drivers/gpu/drm/i915/intel_display.c | 12 ++++++++++++
 drivers/gpu/drm/i915/intel_dp.c      |  4 +++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8c52cbd..bc8ff0a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -672,6 +672,7 @@ enum intel_sbi_destination {
 #define QUIRK_LVDS_SSC_DISABLE (1<<1)
 #define QUIRK_INVERT_BRIGHTNESS (1<<2)
 #define QUIRK_NO_PCH_PWM_ENABLE (1<<3)
+#define QUIRK_IGNORE_VBT_BPP	(1<<4)
 
 struct intel_fbdev;
 struct intel_fbc_work;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 8206ee7..c364377 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10139,6 +10139,15 @@ static void quirk_no_pcm_pwm_enable(struct drm_device *dev)
 	DRM_INFO("applying no-PCH_PWM_ENABLE quirk\n");
 }
 
+/* Some machines (ux31a) advertise the panel should use 18bpp, but it lies.
+ */
+static void quirk_ignore_vbt_bpp(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	dev_priv->quirks |= QUIRK_IGNORE_VBT_BPP;
+	DRM_INFO("applying IGNORE_VBT_BPP quirk\n");
+}
+
 struct intel_quirk {
 	int device;
 	int subsystem_vendor;
@@ -10213,6 +10222,9 @@ static struct intel_quirk intel_quirks[] = {
 	{ 0x0116, 0x1028, 0x052e, quirk_no_pcm_pwm_enable },
 	/* Dell XPS13 HD and XPS13 FHD Ivy Bridge */
 	{ 0x0166, 0x1028, 0x058b, quirk_no_pcm_pwm_enable },
+
+	/* Asus Zenbook UX31A Ivybridge eDP */
+	{ 0x0166, 0x1043, 0x1517, quirk_ignore_vbt_bpp },
 };
 
 static void intel_init_quirks(struct drm_device *dev)
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index 9770160..fd47be8 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -805,7 +805,9 @@ intel_dp_compute_config(struct intel_encoder *encoder,
 	/* Walk through all bpp values. Luckily they're all nicely spaced with 2
 	 * bpc in between. */
 	bpp = pipe_config->pipe_bpp;
-	if (is_edp(intel_dp) && dev_priv->vbt.edp_bpp) {
+	if (is_edp(intel_dp) &&
+	    dev_priv->vbt.edp_bpp &&
+	    (dev_priv->quirks & QUIRK_IGNORE_VBT_BPP) == 0) {
 		DRM_DEBUG_KMS("clamping bpp for eDP panel to BIOS-provided %i\n",
 			      dev_priv->vbt.edp_bpp);
 		bpp = min_t(int, bpp, dev_priv->vbt.edp_bpp);
-- 
1.8.4