From 7bd90909bbf9ce7c40e1da3d72b97b93839c188a Mon Sep 17 00:00:00 2001 From: Carsten Emde Date: Thu, 15 Mar 2012 15:56:25 +0100 Subject: [PATCH] drm/i915: panel: invert brightness via parameter Following the documentation of the Legacy Backlight Brightness (LBB) Register in the configuration space of some Intel PCI graphics adapters, setting the LBB register with the value 0x0 causes the backlight to be turned off, and 0xFF causes the backlight to be set to 100% intensity (http://download.intel.com/embedded/processors/Whitepaper/324567.pdf). The Acer Aspire 5734Z, however, turns the backlight off at 0xFF and sets it to maximum intensity at 0. In consequence, the screen of this systems becomes dark at an early boot stage which makes it unusable. The same inversion applies to the BLC_PWM_CTL I915 register. This problem was introduced in kernel version 2.6.38 when the PCI device of this system was first supported by the i915 KMS module. This patch adds a parameter to the i915 module to enable inversion of the brightness variable (i915.invert_brightness). Signed-off-by: Carsten Emde Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter --- Documentation/kernel-parameters.txt | 9 +++++++++ drivers/gpu/drm/i915/intel_panel.c | 17 +++++++++++++++++ 2 files changed, 26 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 033d4e69b43b..9f6ba8fab088 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -967,6 +967,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN capability is set. + i915.invert_brightness + [DRM] Invert the sense of the variable that is used to + set the brightness of the panel backlight. Normally a + value of 0 indicates backlight switched off, and the + maximum value sets the backlight to maximum brightness. + If this parameter is specified, a value of 0 sets the + backlight to maximum brightness, and the maximum value + switches the backlight off. + icn= [HW,ISDN] Format: [,[,[,]]] diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c index 230a141dbea3..c4b3f349af69 100644 --- a/drivers/gpu/drm/i915/intel_panel.c +++ b/drivers/gpu/drm/i915/intel_panel.c @@ -28,6 +28,7 @@ * Chris Wilson */ +#include #include "intel_drv.h" #define PCI_LBPC 0xf4 /* legacy/combination backlight modes */ @@ -191,6 +192,20 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev) return max; } +static bool i915_panel_invert_brightness; +MODULE_PARM_DESC(invert_brightness, "Invert backlight brightness, please " + "report PCI device ID, subsystem vendor and subsystem device ID " + "to dri-devel@lists.freedesktop.org, if your machine needs it. " + "It will then be included in an upcoming module version."); +module_param_named(invert_brightness, i915_panel_invert_brightness, bool, 0600); +static u32 intel_panel_compute_brightness(struct drm_device *dev, u32 val) +{ + if (i915_panel_invert_brightness) + return intel_panel_get_max_backlight(dev) - val; + + return val; +} + u32 intel_panel_get_backlight(struct drm_device *dev) { struct drm_i915_private *dev_priv = dev->dev_private; @@ -211,6 +226,7 @@ u32 intel_panel_get_backlight(struct drm_device *dev) } } + val = intel_panel_compute_brightness(dev, val); DRM_DEBUG_DRIVER("get backlight PWM = %d\n", val); return val; } @@ -228,6 +244,7 @@ static void intel_panel_actually_set_backlight(struct drm_device *dev, u32 level u32 tmp; DRM_DEBUG_DRIVER("set backlight PWM = %d\n", level); + level = intel_panel_compute_brightness(dev, level); if (HAS_PCH_SPLIT(dev)) return intel_pch_panel_set_backlight(dev, level); -- GitLab