[Intel-gfx] [PATCH 2/3] drm/i915: Fix scanoutpos calculations

Daniel Vetter daniel at ffwll.ch
Sat Oct 12 01:19:04 CEST 2013

On Fri, Oct 11, 2013 at 04:31:38PM +0200, Mario Kleiner wrote:
> Daniel, Ville,
> i tested Ville's patch series for the scanoutpos improvements on a
> GMA-950, on top of airlied's current drm-next branch.
> There's one issue: The variable "position" in
> i915_get_crtc_scanoutpos() must be turned from a u32 into a int,
> otherwise funny sign errors happen and we end up with *vpos being
> off by multiple million scanlines and timestamps being off by over
> 60 seconds.
> Other than that looks good. Execution time is now better:
> Before uncore.lock addition: 3-4 usecs execution time for the
> scanoutpos query on my machine. After uncore.lock addition
> (3.12.0-rc3) 9-20 usecs, sometimes repetition of the timing loop
> triggered. After Ville's patches down to typically 3-8 usecs,
> occassionally spiking to almost 20 usecs.
> I'll make my patches for the realtime kernel + increased accuracy on
> top of drm-next + Ville's patches.

So official reviewed-by/tested-by from you on Ville's latest patches in
this thread?
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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