From: Daniel Vetter Date: Wed, 6 Feb 2013 10:24:41 +0000 (+0100) Subject: drm/i915: write backlight harder X-Git-Tag: v3.9-rc2~15^2~6^2~42 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=cf0a6584aa6d382f802f2c3cacac23ccbccde0cd;p=platform%2Fkernel%2Flinux-stable.git drm/i915: write backlight harder 770c12312ad617172b1a65b911d3e6564fc5aca8 is the first bad commit commit 770c12312ad617172b1a65b911d3e6564fc5aca8 Author: Takashi Iwai Date: Sat Aug 11 08:56:42 2012 +0200 drm/i915: Fix blank panel at reopening lid changed the register write sequence for restoring the backlight, which helped prevent non-working backlights on some machines. Turns out that the original sequence was the right thing to do for a different set of machines. Worse, setting the backlight level _after_ enabling it seems to reset it somehow. So we need to make that one conditional upon the backlight having been reset to zero, and add the old one back. Cargo-culting at it's best, but it seems to work. Cc: stable@vger.kernel.org Cc: Takashi Iwai Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=47941 Reviewed-by: Jani Nikula Acked-by: Takashi Iwai Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index bee8cb6..a3730e0 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -321,6 +321,9 @@ void intel_panel_enable_backlight(struct drm_device *dev, if (dev_priv->backlight_level == 0) dev_priv->backlight_level = intel_panel_get_max_backlight(dev); + dev_priv->backlight_enabled = true; + intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); + if (INTEL_INFO(dev)->gen >= 4) { uint32_t reg, tmp; @@ -356,12 +359,12 @@ void intel_panel_enable_backlight(struct drm_device *dev, } set_level: - /* Call below after setting BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1. - * BLC_PWM_CPU_CTL may be cleared to zero automatically when these - * registers are set. + /* Check the current backlight level and try to set again if it's zero. + * On some machines, BLC_PWM_CPU_CTL is cleared to zero automatically + * when BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1 are written. */ - dev_priv->backlight_enabled = true; - intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); + if (!intel_panel_get_backlight(dev)) + intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); } static void intel_panel_init_backlight(struct drm_device *dev)