[Intel-gfx] [PATCH] drm/i915: Enable scanline read for gen9 dsi

[Saarinen, Jani]

HI, 

> -----Original Message-----
> From: Intel-gfx [mailto:intel-gfx-bounces at lists.freedesktop.org] On Behalf Of
> Ville Syrjälä
> Sent: perjantai 8. syyskuuta 2017 17.55
> To: Srinivas, Vidya <vidya.srinivas at intel.com>
> Cc: intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH] drm/i915: Enable scanline read for gen9 dsi
> 

> 
> Another thought that just occurred to me: Maybe we could use these
> timestamps as a workaround for the DDI "scanline reads as 0 at the wrong
> time" problem. What we could do is check of the scanline counter reads as 0,
> and if it does we could switch over to checking the timestamps instead. Not
> sure if we should just do the full timestamp based scanline read like you do
> here, or we could just check that if the timestamps look like they're close to
> vblank_start we just return vblank_start-1. This could then remove the
> obnoxious retry loop from the scanline counter read.
> 
Also please use trybot also as dsi system not in pw runs due to known issue.

> --
> Ville Syrjälä
> Intel OTC


Jani Saarinen
Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo