From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH] drm/i915: rc6 residency (fix the fix)
Date: Mon, 23 Apr 2012 09:38:33 +0200
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To: Ben Widawsky <ben@bwidawsk.net>
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On Sun, Apr 22, 2012 at 07:57:33PM -0700, Ben Widawsky wrote:
> On Sun, 22 Apr 2012 18:39:23 +0100
> Chris Wilson <chris@chris-wilson.co.uk> wrote:
> 
> > On Sun, 22 Apr 2012 10:35:29 -0700, Ben Widawsky <ben@bwidawsk.net>
> > wrote:
> > > On Sun, 22 Apr 2012 16:49:53 +0100
> > > Chris Wilson <chris@chris-wilson.co.uk> wrote:
> > > 
> > > > On Fri, 20 Apr 2012 11:50:01 -0700, Ben Widawsky
> > > > <ben@bwidawsk.net> wrote:
> > > > > Chris' fix for my 32b breakage was incorrect. do_div returns a
> > > > > remainder. Go back to a divide macro which is more 32b friendly.
> > > > > 
> > > > > Tested on x86-64.
> > > > > 
> > > > > This has only been compile tested on 32b systems.
> > > > Doesn't compile on my 32-bit systems.
> > > > 
> > > > Still does a 64-bit divide.
> > > 
> > > This is weird. I don't understand what's broken exactly. It should
> > > be dividing an unsigned long long, which the 32b compiler should
> > > have no issue with. The macro itself expands to do_div which was
> > > your original fix.
> > > 
> > > What is the error message you get?
> > Undefined reference to __udivid3.
> > 
> > The reason is that the result of DIV_ROUND_UP_ULL is a 64-bit value,
> > which we then proceed to divide by 100.
> > -Chris
> > 
> 
> For the sake of picking nits, this is a linker fail, not a compiler one.
> The only reason I make note of it is I was only compiling the .ko when
> I did my testing.
> 
> So lesson learned, can't we just:

Done.
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48