[Intel-gfx] [PATCH 2/6] drm/i915: Catch INVALID_PIPE in vlv_get_backlight()

[Jani Nikula]

On Fri, 07 Nov 2014, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> When the display is off, we can't read out the current backlight level
> from the hardware since we have no pipe to do so. Catch the INVALID_PIPE
> in vlv_get_backlight() rather than pass it to VLV_BLC_PWM_CTL() which
> would obviously end accessing some bogus register.
>
> This problem can be reproduced simply by reading the backlight device
> actual_brightness file while the display is off.

I think we should check for panel->backlight.enabled in
intel_panel_get_backlight instead. I think it would be the right thing
to do independent of the issue you found, but I think it also fixes your
issue.

BR,
Jani.


>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_panel.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index ef646b1..847d00f9 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -532,6 +532,9 @@ static u32 vlv_get_backlight(struct intel_connector *connector)
>  	struct drm_device *dev = connector->base.dev;
>  	enum pipe pipe = intel_get_pipe_from_connector(connector);
>  
> +	if (pipe == INVALID_PIPE)
> +		return 0;
> +
>  	return _vlv_get_backlight(dev, pipe);
>  }
>  
> -- 
> 2.0.4
>
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-- 
Jani Nikula, Intel Open Source Technology Center