Re: [PATCH] drm: Add downclock quirk for Samsung LTN121AT10-301

[Adam Jackson <ajax@redhat.com>]

On 5/30/12 8:05 AM, Sean Paul wrote:

> Yes, definitely. The reason I can't set it via xrandr (easily) is
> because we look for lvds downclock modes (in i915) on the driver init.
> Since the driver initializes way before we have a chance to add a new
> mode via xrandr, the driver won't have a downclock mode.
>
> I suppose the other option is to hack the i915 driver to allow a
> downclocked mode to be added after it's been initialized. I haven't
> looked into this solution, it might be worth investigating.

Just so I'm clear, is what you're looking for "I want this pair of 
timings, with the driver magically switching between them"?  If all you 
wanted was the lower clock speed all the time you could just, you know, 
do that, so I assume that's not what you're after.

If binding two timings together like that is what you want, then that 
seems like a pretty reasonable device-specific ioctl at first glance.  I 
think the only thing to be careful of would be copying the slower 
timings into the driver private of the faster, rather than keeping a 
pointer or copy of the object id, since modes aren't refcounted.

How big of a power savings do you see with this?  Wondering if it's 
worth trying to make some common tooling for finding downclocked modes, 
if it's going to be worthwhile on multiple panels.

- ajax