linux-kernel - [PATCH 3.14 38/94] drm/i915: set backlight duty cycle after backlight enable for gen4

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Message-Id: <20140707235757.912299937@linuxfoundation.org>
Date:	Mon,  7 Jul 2014 16:57:28 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Daniel Vetter <daniel.vetter@...ll.ch>,
	Jani Nikula <jani.nikula@...el.com>
Subject: [PATCH 3.14 38/94] drm/i915: set backlight duty cycle after backlight enable for gen4

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 2e7eeeb59a92d09144fdb7d2dc1af77a10a7945b upstream.

For reasons I can't claim to fully understand gen4 seems to require
backlight duty cycle setting after the backlight has been enabled, or
else black screen follows. I don't have documentation for the correct
sequence on gen4 either. Confirmed on Dell Latitude D630 and MacBook4,1.

This fixes a regression introduced by
commit b35684b8fa94e04f55fd38bf672b737741d2f9e2
Author: Jani Nikula <jani.nikula@...el.com>
Date:   Thu Nov 14 12:13:41 2013 +0200

    drm/i915: do full backlight setup at enable time

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=75791
Reported-and-tested-by: mcy@....fr
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79423
Reported-and-tested-by: Marc Milgram <mmilgram@...hat.com>
Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/intel_panel.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -736,9 +736,6 @@ static void i965_enable_backlight(struct
 	ctl = freq << 16;
 	I915_WRITE(BLC_PWM_CTL, ctl);
 
-	/* XXX: combine this into above write? */
-	intel_panel_actually_set_backlight(connector, panel->backlight.level);
-
 	ctl2 = BLM_PIPE(pipe);
 	if (panel->backlight.combination_mode)
 		ctl2 |= BLM_COMBINATION_MODE;
@@ -747,6 +744,8 @@ static void i965_enable_backlight(struct
 	I915_WRITE(BLC_PWM_CTL2, ctl2);
 	POSTING_READ(BLC_PWM_CTL2);
 	I915_WRITE(BLC_PWM_CTL2, ctl2 | BLM_PWM_ENABLE);
+
+	intel_panel_actually_set_backlight(connector, panel->backlight.level);
 }
 
 static void vlv_enable_backlight(struct intel_connector *connector)


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