releases/3.14.5/drm-i915-restore-quirk_no_pch_pwm_enable.patch

From jani.nikula@intel.com  Wed May 14 12:59:07 2014
From: Jani Nikula <jani.nikula@intel.com>
Date: Mon, 28 Apr 2014 13:10:07 +0300
Subject: [PATCH for stable 3.14 only 1/1] drm/i915: restore QUIRK_NO_PCH_PWM_ENABLE
To: stable@vger.kernel.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: intel-gfx@lists.freedesktop.org, daniel@ffwll.ch, Romain Francoise <romain@orebokech.com>, Kamal Mostafa <kamal@canonical.com>, jani.nikula@intel.com
Message-ID: <b6e9694e03367a3133511f7093c917b4982f1266.1398678778.git.jani.nikula@intel.com>

From: Jani Nikula <jani.nikula@intel.com>

This reverts the bisected regressing

commit bc0bb9fd1c7810407ab810d204bbaecb255fddde
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Thu Nov 14 12:14:29 2013 +0200

    drm/i915: remove QUIRK_NO_PCH_PWM_ENABLE

restoring QUIRK_NO_PCH_PWM_ENABLE for a couple of Dell XPS models which
broke in 3.14.

There is no such revert upstream. We have root caused and fixed the
issue upstream, without the quirk, with:

commit 39fbc9c8f6765959b55e0b127dd5c57df5a47d67
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:22:06 2014 +0300

    drm/i915: check VBT for supported backlight type

and

commit c675949ec58ca50d5a3ae3c757892f1560f6e896
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Apr 9 11:31:37 2014 +0300

    drm/i915: do not setup backlight if not available according to VBT

While the commits are within the stable rules otherwise, and fix more
machines than just the regressed Dell XPS models, we feel backporting
them to stable may be too risky. The revert is limited to the broken
machines, and the impact should be effectively the same as what the
upstream commits do more generally.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76276
Reported-by: Romain Francoise <romain@orebokech.com>
Acked-by: Daniel Vetter <daniel@ffwll.ch>
Tested-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Romain Francoise <romain@orebokech.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/i915_drv.h      |    1 +
 drivers/gpu/drm/i915/intel_display.c |   16 ++++++++++++++++
 drivers/gpu/drm/i915/intel_panel.c   |    4 ++++
 3 files changed, 21 insertions(+)

--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -734,6 +734,7 @@ enum intel_sbi_destination {
 #define QUIRK_PIPEA_FORCE (1<<0)
 #define QUIRK_LVDS_SSC_DISABLE (1<<1)
 #define QUIRK_INVERT_BRIGHTNESS (1<<2)
+#define QUIRK_NO_PCH_PWM_ENABLE (1<<3)
 
 struct intel_fbdev;
 struct intel_fbc_work;
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -10771,6 +10771,17 @@ static void quirk_invert_brightness(stru
 	DRM_INFO("applying inverted panel brightness quirk\n");
 }
 
+/*
+ * Some machines (Dell XPS13) suffer broken backlight controls if
+ * BLM_PCH_PWM_ENABLE is set.
+ */
+static void quirk_no_pcm_pwm_enable(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	dev_priv->quirks |= QUIRK_NO_PCH_PWM_ENABLE;
+	DRM_INFO("applying no-PCH_PWM_ENABLE quirk\n");
+}
+
 struct intel_quirk {
 	int device;
 	int subsystem_vendor;
@@ -10839,6 +10850,11 @@ static struct intel_quirk intel_quirks[]
 
 	/* Acer Aspire 4736Z */
 	{ 0x2a42, 0x1025, 0x0260, quirk_invert_brightness },
+
+	/* Dell XPS13 HD Sandy Bridge */
+	{ 0x0116, 0x1028, 0x052e, quirk_no_pcm_pwm_enable },
+	/* Dell XPS13 HD and XPS13 FHD Ivy Bridge */
+	{ 0x0166, 0x1028, 0x058b, quirk_no_pcm_pwm_enable },
 };
 
 static void intel_init_quirks(struct drm_device *dev)
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -671,6 +671,10 @@ static void pch_enable_backlight(struct
 	pch_ctl2 = panel->backlight.max << 16;
 	I915_WRITE(BLC_PWM_PCH_CTL2, pch_ctl2);
 
+	/* XXX: transitional */
+	if (dev_priv->quirks & QUIRK_NO_PCH_PWM_ENABLE)
+		return;
+
 	pch_ctl1 = 0;
 	if (panel->backlight.active_low_pwm)
 		pch_ctl1 |= BLM_PCH_POLARITY;