linux-kernel - Re: [PATCH] drm/i915: fix regression after clock gating init split

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Date:	Sat, 28 May 2011 14:26:28 +1000
From:	Jason Stubbs <jasonbstubbs@...il.com>
To:	Keith Packard <keithp@...thp.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/i915: fix regression after clock gating init split

On Sat, 28 May 2011 05:44:11 Keith Packard wrote:
> On Fri, 27 May 2011 23:44:19 +1000, Jason Stubbs <jasonbstubbs@...il.com> 
wrote:
> > From: Jason Stubbs <jasonbstubbs@...il.com>
> > 
> > However, there are some code paths, notably IS_PINEVIEW(dev), where 
> > init_clock_gating is not set and not needed.
> 
> Looks like Pineview should be using the gen3_init_clock_gating function.

Yep, you are right. Adding printk()s to the original implementation confirmed 
that - at least on my hardware. I should have known to check that...

There are two other code paths where an init_clock_gating function isn't 
specified though. The specific code paths are:

HAS_PCH_SPLIT() && !IS_GEN5() && !IS_GEN6() && !IS_IVYBRIDGE()

Looking at the original intel_enable_clock_gating() function, there would
have been some intialization done for this case.

IS_GEN4() && !IS_CRESTLINE() && !IS_BROADWATER()

It looks like this would have gone into the final "no gating match" if/else 
branch.

If both of the above don't happen in the real world, then I guess it's fine as 
is. If either are possible, then they need to be fixed too.

I'll just (re)send a patch for the IS_PINEVIEW() case and leave the above to
somebody who knows better than I...

Regards,
Jason Stubbs
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