From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>
Subject: Re: [PATCH] drm/i915: Fix context size calculation on
 SNB/IVB/VLV
Date: Thu, 22 Aug 2013 21:52:53 +0300
Message-ID: <20130822185253.GF29682@intel.com>
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To: Ben Widawsky <ben@bwidawsk.net>
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On Thu, Aug 22, 2013 at 11:30:55AM -0700, Ben Widawsky wrote:
> On Thu, Aug 22, 2013 at 07:23:13PM +0300, ville.syrjala@linux.intel.com w=
rote:
> > From: Ville Syrj=E4l=E4 <ville.syrjala@linux.intel.com>
> > =

> > All the different context sizes reported in the CXT_SIZE register
> > aren't meant to be simply added together.
> > =

> > While BSpec is somewhat unclear on the topic of the actual context
> > size, empirical tests have now revealed the truth. So let's add a
> > big fat comment to remind people how it all works.
> =

> By the way. I've done some digging. I believe (75% certain) pre-HSW,
> every context save writes the entire data. So if you wanted to set some
> pattern and see what HW actually overwrites, it should be doable. HSW+
> though we can't do that.

Ah right, so you were thinking of initializing the context w/ some
poison, and then see how much is left after the HW has saved. That I
didnb't actually do. Should be reasonable trivial though, so I guess
I'll try it. The same method could also be used to identify whether
HSW skips parts or rearranges the context dynamically.

-- =

Ville Syrj=E4l=E4
Intel OTC