linux-kernel - Re: i915/kms/backlight-combo mode problem

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Date:	Mon, 09 May 2011 11:00:10 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	"Joey Lee" <jlee@...ell.com>
Cc:	<melchior.franz@...il.com>, <chris@...is-wilson.co.uk>,
	<dri-devel@...ts.freedesktop.org>, "Joey Lee" <JLee@...ell.com>,
	"Michael Chang" <MChang@...ell.com>, <linux-kernel@...r.kernel.org>
Subject: Re: i915/kms/backlight-combo mode problem

At Mon, 09 May 2011 02:50:50 -0600,
Joey Lee wrote:
> 
> Add Cc. Michael Chang for he is our i915 expert.
> 
> Hi Melchior, 
> 
> 於 日，2011-05-08 於 16:05 +0200，Melchior FRANZ 提到：
> > 
> > > Does it work to you direct control brightness by access
> > > by /sys/class/backlight/acer-wmi/brightness ?
> > 
> > No. A number written to this virtual file is accepted and remembered,
> > but it doesn't actually change the brightness. It takes setpci to do
> > that. 
> > 
> 
> I thought the video driver still is the KEY component for backlight
> issues, need fix the problem in video driver first.
> 
> > 
> >  
> > > As I remember, use setpci to control brightness is not recommended
> > > because BIOS or ACPI will also touch brightness level. That will be
> > > better control brightness by the function that was provided by BIOS. 
> > > e.g. ACPI or WMI interface, or direct control by EC.
> > 
> > Well, sounds plausible. And I wouldn't do it if it weren't the only
> > way at the moment.  :-)
> > 
> > 
> > 
> > > That means that will be better fix your Fn key control brightness like
> > > before, you just need press Fn key to change brightness and don't need
> > > have any workaround.
> > 
> > OK. I have added a lot of debug messages to intel_panel.c yesterday.
> > All it told me was that it seems to work correctly wiht acpi_osi=Linux.
> > Except that it doesn't actually change the brightness. Without acpi_osi
> > the functions aren't called at all and none of my messages showed up.
> > 
> 
> I traced _Q event in your DSDT, when acpi_osi=Linux, it run the Intel
> OpRegion logic for change brightness. And, finally, intel_opregion will
> access the function the were provided by intel_panel. So, the problem
> still back to intel_panel.
> 
> After discuss with Michael chang, we thought there have problem in your
> brightness level after add combination mode:
> 
> vi driver/gpu/drm/i915/intel_panel.c
> 
> void intel_panel_set_backlight(struct drm_device *dev, u32 level)
> {
>         struct drm_i915_private *dev_priv = dev->dev_private;
>         u32 tmp;
> 
>         DRM_DEBUG_DRIVER("set backlight PWM = %d\n", level);
> 
>         if (HAS_PCH_SPLIT(dev))
>                 return intel_pch_panel_set_backlight(dev, level);
> 
>         if (is_backlight_combination_mode(dev)){
>                 u32 max = intel_panel_get_max_backlight(dev);
>                 u8 lbpc;
> 
>                 lbpc = level * 0xfe / max + 1;
>                 level /= lbpc;			/* maybe the level changed by lbpc */
>                 pci_write_config_byte(dev->pdev, PCI_LBPC, lbpc);
>         }
> 
>         tmp = I915_READ(BLC_PWM_CTL);
>         if (IS_PINEVIEW(dev)) {
>                 tmp &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1);
>                 level <<= 1;
>         } else
>                 tmp &= ~BACKLIGHT_DUTY_CYCLE_MASK;
>         I915_WRITE(BLC_PWM_CTL, tmp | level);
> }
> 
> We need to know some run time value when intel_panel_set_backlight call by funciton key.

Yes, that'll help understanding.

> Please help to apply the attached debug patch to intel_panel.c then attached dmesg.

The patch has an obvious typo :)
Also, we should track the value in intel_panel_get_backlight(), too.


Takashi


> > > Looks like current status is we try to fix bko#31522 but the patch
> > > causes your brightness no work by press Fn key even with acpi_osi=Linux.
> > > Does it right?
> > 
> > The history is: with acpi_osi=Linux everything worked with 2.6.38-rc8.
> > With 2.6.38 the screen stayed black. The patch that only ignored lbpc=0
> > worked (IIRC) including key adjustment. Later patches broke keys.
> > 
> > 
> > 
> > > 	replace acpi_osi=Linux by acpi_osi="!Windows 2006"
> > > 
> > > Does it also works to you for backlight control?
> > 
> > No, doesn't work.
> > 
> 
> We can test the acpi_osi="!Windows 2006" again after we fix the i915's
> problem.
> 
> 
> Thank's
> Joey Lee
> 
> The following is debug patch, and please add kernel parameter
> drm.debug=0x02 :
> 
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index f8f86e5..f62dbd9 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -236,17 +236,22 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level)
>  		u32 max = intel_panel_get_max_backlight(dev);
>  		u8 lbpc;
>  
> +		DRM_DEBUG_DRIVER("set backlight max = % 		lbpc = level * 0xfe / max + 1;
> +		DRM_DEBUG_DRIVER("set backlight lbpc = %d\n", lbpc);
>  		level /= lbpc;
>  		pci_write_config_byte(dev->pdev, PCI_LBPC, lbpc);
>  	}
>  
>  	tmp = I915_READ(BLC_PWM_CTL);
> +	DRM_DEBUG_DRIVER("set backlight tmp(1) = %d\n", tmp);
>  	if (IS_PINEVIEW(dev)) {
>  		tmp &= ~(BACKLIGHT_DUTY_CYCLE_MASK - 1);
>  		level <<= 1;
>  	} else
>  		tmp &= ~BACKLIGHT_DUTY_CYCLE_MASK;
> +	DRM_DEBUG_DRIVER("set backlight tmp(2) = %d\n", tmp);
> +	DRM_DEBUG_DRIVER("set backlight level = %d\n", level);
>  	I915_WRITE(BLC_PWM_CTL, tmp | level);
>  }
>  
> 
> 
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