[Intel-gfx] [PATCH] drm/i915: Redo WMs when cursor size changes

[Joe Konno]

On 02/27/2015 06:53 AM, Daniel Vetter wrote:
> On Thu, Feb 26, 2015 at 05:47:35PM -0800, Matt Roper wrote:
>> So your patch below could result in sleeps happening while vblanks are
>> disabled, which is bad (IIRC, most of those sleeps are in the SKL
>> codepath right now, but I think there's a workaround-related wait for
>> IVB as well).
>>
>> Our watermark code needs a lot of work to beat it into proper shape for
>> atomic and that's what I'm working on at the moment.
> 
> Alternative issue is that wm recompute happens before we update all the
> legacy state. Tvrkto just stumbled over that for some of his skl watermark
> code, he had to switch a few places in the wm code from looking at
> plane->fb to look at plane->state->fb.
> 
> Similar changes might be needed for the cursor wm code -
> cursor_width/height is kinda redundant since universal planes support.

Thanks for the insights, Matt and Dan. It's clear to me from Matt's analysis
that my patch is a hack at best and nowhere near a proper fix.

This patch was submitted in the hopes of fixing a substantial graphical
regression. Shall my patch be retooled as a "better" work-around, or will the
regression stand until the watermark code is beat into proper shape?