[Intel-gfx] [PATCH 1/2] drm/i915: Enable LVDS downclock feature for LVDS

[Jesse Barnes]

On Tue, 17 Nov 2009 17:12:42 +0800
yakui.zhao at intel.com wrote:

> From: Zhao Yakui <yakui.zhao at intel.com>
> 
> If more than one mode with the same resolution defined in EDID has
> different refresh rate, it is thought that the downclock is found for
> LVDS. We will program the different FPx0/1 register so that we can
> select dynamically between the low and high frequency.

Cool, we've been wanting this for awhile.
 
> On the g4x platform we will use the CxSR feature to switch the
> different refresh rate if the LVDS downclock feature is supported.

Great, may as well use the hardware when available...

> @@ -539,6 +539,8 @@ typedef struct drm_i915_private {
>  	/* Reclocking support */
>  	bool render_reclock_avail;
>  	bool lvds_downclock_avail;
> +	/* indicates the reduced downclock for LVDS*/
> +	int	lvds_downclock;

Weird indentation, a single space should be sufficient.

>  /**
> + * intel_find_lvds_downclock - find the reduced downclock for LVDS
> in EDID
> + * @dev: drm device
> + * @connector: LVDS connector
> + *
> + * Find the reduced downclock for LVDS in EDID.
> + */
> +static void intel_find_lvds_downclock(struct drm_device *dev,
> +				struct drm_connector *connector)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct drm_display_mode *scan, *panel_fixed_mode;
> +
> +	panel_fixed_mode = dev_priv->panel_fixed_mode;
> +	list_for_each_entry(scan, &connector->probed_modes, head) {
> +		mutex_lock(&dev->mode_config.mutex);

We need to take the mutex across the whole scan, otherwise the list may
change under us.

> @@ -1023,6 +1065,7 @@ void intel_lvds_init(struct drm_device *dev)
>  			dev_priv->panel_fixed_mode =
>  				drm_mode_duplicate(dev, scan);
>  			mutex_unlock(&dev->mode_config.mutex);
> +			intel_find_lvds_downclock(dev, connector);
>  			goto out;
>  		}
>  		mutex_unlock(&dev->mode_config.mutex);

Is there a VBT equivalent?  Most of our panel timings come from VBT, so
if we only support EDID we won't enable the feature very often (it's
fine to add that as a separate patch though).

Assuming you fix the above, you can add my Reviewed-by to the patch.

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center