| Message ID | 1379705747-16858-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c index e27c170..6d708d7 100644 --- a/drivers/gpu/drm/i915/intel_opregion.c +++ b/drivers/gpu/drm/i915/intel_opregion.c @@ -163,7 +163,7 @@ static u32 asle_set_backlight(struct drm_device *dev, u32 bclp) max = intel_panel_get_max_backlight(dev); intel_panel_set_backlight(dev, bclp * max / 255); - iowrite32((bclp*0x64)/0xff | ASLE_CBLV_VALID, &asle->cblv); + iowrite32(DIV_ROUND_UP(bclp * 100, 255) | ASLE_CBLV_VALID, &asle->cblv); return 0; }
This is a note to let you know that I have just added a patch titled drm/i915: try not to lose backlight CBLV precision to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From 63087102908b53cbff24c68c0b48464e2dc31c31 Mon Sep 17 00:00:00 2001 From: Jani Nikula <jani.nikula@intel.com> Date: Fri, 23 Aug 2013 10:50:39 +0300 Subject: [PATCH] drm/i915: try not to lose backlight CBLV precision commit cac6a5ae0118832936eb162ec4cedb30f2422bcc upstream. ACPI has _BCM and _BQC methods to set and query the backlight brightness, respectively. The ACPI opregion has variables BCLP and CBLV to hold the requested and current backlight brightness, respectively. The BCLP variable has range 0..255 while the others have range 0..100. This means the _BCM method has to scale the brightness for BCLP, and the gfx driver has to scale the requested value back for CBLV. If the _BQC method uses the CBLV variable (apparently some implementations do, some don't) for current backlight level reporting, there's room for rounding errors. Use DIV_ROUND_UP for scaling back to CBLV to get back to the same values that were passed to _BCM, presuming the _BCM simply uses bclp = (in * 255) / 100 for scaling to BCLP. Reference: https://gist.github.com/aaronlu/6314920 Reported-by: Aaron Lu <aaron.lu@intel.com> Signed-off-by: Jani Nikula <jani.nikula@intel.com> Reviewed-by: Aaron Lu <aaron.lu@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> [ luis: backported to 3.5: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/gpu/drm/i915/intel_opregion.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) -- 1.8.3.2