Re: Thinkpad T420 and single/dual channel lvds

[Chris Wilson <chris@chris-wilson.co.uk>]

On Thu, 15 Mar 2012 14:15:54 +0100, Takashi Iwai <tiwai@suse.de> wrote:
> +static bool is_dual_link_lvds(struct drm_i915_private *dev_priv)
> +{
> +	/* BIOS should set the proper LVDS register value at boot, but
> +	 * in reality, it doesn't set the value when the lid is closed;
> +	 * thus when a machine is booted with the lid closed, the LVDS
> +	 * reg value can't be trusted.  So we need to check "the value
> +	 * to be set" in VBT at first.
> +	 */
> +	if ((dev_priv->bios_lvds_val & LVDS_CLKB_POWER_MASK) ==
> +	    LVDS_CLKB_POWER_UP)
> +		return true;
> +	if ((I915_READ(PCH_LVDS) & LVDS_CLKB_POWER_MASK) ==

This is either PCH_LVDS or LVDS depending on the generation.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre