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* [PATCH] drm/i915: fix backlight after resume on 855gm
@ 2015-06-26 10:54 ` Jani Nikula
  0 siblings, 0 replies; 9+ messages in thread
From: Jani Nikula @ 2015-06-26 10:54 UTC (permalink / raw)
  To: intel-gfx; +Cc: ville.syrjala, chris, stable, phg, jani.nikula

Some 855gm models (at least ThinkPad X40) regressed because of

commit b0cd324faed23d10d66ba6ade66579c681feef6f
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Wed Nov 12 16:25:43 2014 +0200

    drm/i915: don't save/restore backlight hist ctl registers

which tried to make our driver more robust by not blindly saving and
restoring registers, but it failed to take into account

commit 0eb96d6ed38430b72897adde58f5477a6b71757a
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Wed Oct 14 12:33:41 2009 -0700

    drm/i915: save/restore BLC histogram control reg across suspend/resume

Fix the regression by enabling hist ctl on gen2.

v2: Improved the comment.

Reported-and-tested-by: Philipp Gesang <phg@phi-gamma.net>
References: http://mid.gmane.org/20150623222648.GD12335@acheron
Fixes: b0cd324faed2 ("drm/i915: don't save/restore backlight hist ctl registers")
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: stable@vger.kernel.org
Acked-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h    | 1 +
 drivers/gpu/drm/i915/intel_panel.c | 7 +++++++
 2 files changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index fa9ccb87eb66..bf7c08b94088 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3507,6 +3507,7 @@ enum skl_disp_power_wells {
 #define   BLM_POLARITY_PNV			(1 << 0) /* pnv only */
 
 #define BLC_HIST_CTL	(dev_priv->info.display_mmio_offset + 0x61260)
+#define  BLM_HISTOGRAM_ENABLE			(1 << 31)
 
 /* New registers for PCH-split platforms. Safe where new bits show up, the
  * register layout machtes with gen4 BLC_PWM_CTL[12]. */
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 7d83527f95f7..a55477c59559 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -907,6 +907,13 @@ static void i9xx_enable_backlight(struct intel_connector *connector)
 
 	/* XXX: combine this into above write? */
 	intel_panel_actually_set_backlight(connector, panel->backlight.level);
+
+	/*
+	 * Needed to enable backlight on some 855gm models. Checking for gen2 is
+	 * safe, as 855gm is the only gen2 that has backlight.
+	 */
+	if (IS_GEN2(dev))
+		I915_WRITE(BLC_HIST_CTL, BLM_HISTOGRAM_ENABLE);
 }
 
 static void i965_enable_backlight(struct intel_connector *connector)
-- 
2.1.4


^ permalink raw reply related	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2015-06-29 11:30 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-06-26 10:54 [PATCH] drm/i915: fix backlight after resume on 855gm Jani Nikula
2015-06-26 10:54 ` Jani Nikula
2015-06-26 11:03 ` Chris Wilson
2015-06-26 11:03   ` Chris Wilson
2015-06-26 11:18   ` [PATCH v3] " Jani Nikula
2015-06-28 17:12     ` shuang.he
2015-06-29 11:32     ` Jani Nikula
2015-06-29 11:32       ` Jani Nikula
2015-06-28 12:08 ` [PATCH] " shuang.he

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