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@xxxxxxxxx>
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@xxxxxx
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=79423
Reported-and-tested-by: Marc Milgram <mmilgram@xxxxxxxxxx>
Cc: Stable <stable@xxxxxxxxxxxxxxx> # 3.14+
Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_panel.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 5e6c888b4928..38a98570d10c 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -798,9 +798,6 @@ static void i965_enable_backlight(struct intel_connector *connector)
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;
@@ -809,6 +806,8 @@ static void i965_enable_backlight(struct intel_connector *connector)
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)
--
1.9.1
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