From: Jesse Barnes <jbarnes@virtuousgeek.org>
To: Eric Anholt <eric@anholt.net>
Cc: Ben Widawsky <ben@bwidawsk.net>,
"drivers, Intel" <Intel-gfx@lists.freedesktop.org>
Subject: Re: Is MI_FLUSH_ENABLE bit 12?
Date: Mon, 5 Dec 2011 14:57:09 -0800 [thread overview]
Message-ID: <20111205145709.5a12cee4@jbarnes-desktop> (raw)
In-Reply-To: <87ipm1cm3c.fsf@eliezer.anholt.net>
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On Wed, 30 Nov 2011 13:54:47 -0800
Eric Anholt <eric@anholt.net> wrote:
> On Wed, 30 Nov 2011 03:42:00 +0000, Ben Widawsky <ben@bwidawsk.net> wrote:
> Non-text part: multipart/signed
> > On Tue, Nov 29, 2011 at 04:47:57PM -0800, Eric Anholt wrote:
> > > On Mon, 28 Nov 2011 18:48:04 -0800, "Keith Packard" <keithp@keithp.com> wrote:
> > > Non-text part: multipart/mixed
> > > Non-text part: multipart/signed
> > > >
> > > > Just reading through vol1c.4 of the bspec this evening and found something odd.
> > > >
> > > > Bit 11 of MI_MODE is "Invalidate UHPTR enable".
> > > > Bit 12 of MI_MODE is "MI_FLUSH Enable"
> > > >
> > > > And, yet, in i915_reg.h:
> > > >
> > > > #define MI_MODE 0x0209c
> > > > # define VS_TIMER_DISPATCH (1 << 6)
> > > > # define MI_FLUSH_ENABLE (1 << 11)
> > > >
> > > > Are we off-by-one on MI_FLUSH_ENABLE? Seems like this would cause
> > > > serious problems...
> > >
> > > I think we are. On the other hand, based on actual behavior plus
> > > reading of simulator, I believe that the bit does nothing, regardless.
> >
> > I do not think so. We've (Chris, I, and perhaps Jesse?) been through
> > this excercise at least twice before, and both times resulted in hangs
> > when we switched to bit 12 on Ironlake, not sure about other platforms.
>
> There is no MI_FLUSH enable bit on Ironlake in my copy of the docs. Bit
> 12 is MBZ on that hardware.
It's one of those "been there forever" bits. A comment wouldn't hurt,
but we should also put in a doc change request (in fact I think I did
that but it went into a black hole).
--
Jesse Barnes, Intel Open Source Technology Center
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next prev parent reply other threads:[~2011-12-05 22:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-29 2:48 Is MI_FLUSH_ENABLE bit 12? Keith Packard
2011-11-30 0:47 ` Eric Anholt
2011-11-30 3:42 ` Ben Widawsky
2011-11-30 8:08 ` Keith Packard
2011-11-30 21:54 ` Eric Anholt
2011-12-05 22:57 ` Jesse Barnes [this message]
2011-12-06 19:56 ` Eric Anholt
2011-12-06 20:21 ` Jesse Barnes
2011-12-06 21:04 ` Daniel Vetter
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