From b285a5939f09afeaecd384c31a1b12e410c29c56 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Fri, 22 Mar 2013 15:44:46 +0100 Subject: [PATCH] Revert "drm/i915: write backlight harder" This reverts commit 0ac8d4bfeec27061ee99ca18c0dbe51f4f8384cd. Turns out that cargo-culting breaks systems. Note that we can't revert further, since commit 02ae6fd77749087cf17f4b18e5a4b7183a6d26da Author: Takashi Iwai Date: Sat Aug 11 08:56:42 2012 +0200 drm/i915: Fix blank panel at reopening lid fixed a regression in 3.6-rc kernels for which we've never figured out the exact root cause. But some further inspection of the backlight code reveals that it's seriously lacking locking. And especially the asle backlight update is know to get fired (through some smm magic) when writing specific backlight control registers. So the possibility of suffering from races is rather real. Until those races are fixed I don't think it makes sense to try further hacks. Which sucks a bit, but sometimes that's how it is :( References: http://www.mail-archive.com/intel-gfx@lists.freedesktop.org/msg18788.html Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=47941 Tested-by: Takashi Iwai Cc: Jani Nikula Cc: Takashi Iwai Cc: stable@vger.kernel.org (the reverted commit was cc: stable, too) Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_panel.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index a3730e0289e5e..bee8cb6108a7d 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -321,9 +321,6 @@ 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; @@ -359,12 +356,12 @@ void intel_panel_enable_backlight(struct drm_device *dev, } set_level: - /* 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. + /* 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. */ - if (!intel_panel_get_backlight(dev)) - intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); + dev_priv->backlight_enabled = true; + intel_panel_actually_set_backlight(dev, dev_priv->backlight_level); } static void intel_panel_init_backlight(struct drm_device *dev) -- 2.39.5