linux-kernel - Re: [PATCH] drm/i915: Fix single msg gmbus

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Message-ID: <20120213222623.GN5301@phenom.ffwll.local>
Date:	Mon, 13 Feb 2012 23:26:23 +0100
From:	Daniel Vetter <daniel@...ll.ch>
To:	Chris Wilson <chris@...is-wilson.co.uk>
Cc:	Daniel Vetter <daniel@...ll.ch>,
	Benson Leung <bleung@...omium.org>, keithp@...thp.com,
	airlied@...ux.ie, djkurtz@...omium.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/i915: Fix single msg gmbus_xfers writes

On Mon, Feb 13, 2012 at 09:49:35PM +0000, Chris Wilson wrote:
> On Mon, 13 Feb 2012 21:38:38 +0100, Daniel Vetter <daniel@...ll.ch> wrote:
> > This here looks like just a white-space change. But your commit message
> > sounds like it's not jsut write's that are affected by this issue and need
> > to be fixed. Can you please clear up this for easily confused me?
> 
> It makes the write path similar to the read path. I admit to overlooking
> the single write message as everything I saw was always a write followed
> by a read. The patch looks correct, but I need to stare at it a bit more
> before I r-b.
> 
> However, the outstanding issue is that we need to separate the gmbus
> i2c adapter from the gpio i2c adapter in order for the pairing to work
> with the expectations of the i2c core.

There's another patch floating on dri-devel to add a gmbus_mutex. The
issue it tries to avoid is that multiple users corrupting each anothers
state when using the single gmbus controller. See "[PATCH] [PATCH]
drm/i915: Fix race condition in accessing GMBUS". Or have you thought of
another interaction that we need to sort out?
-Daniel
-- 
Daniel Vetter
Mail: daniel@...ll.ch
Mobile: +41 (0)79 365 57 48
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