From: Daniel Vetter <daniel@ffwll.ch>
To: "Eoff, Ullysses A" <ullysses.a.eoff@intel.com>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [PATCH 1/2 v3] drm/i915: intel_backlight scale() math WA
Date: Tue, 30 Sep 2014 18:31:35 +0200 [thread overview]
Message-ID: <20140930163135.GC12343@phenom.ffwll.local> (raw)
In-Reply-To: <1412089133.12349.49.camel@localhost>
On Tue, Sep 30, 2014 at 02:58:54PM +0000, Eoff, Ullysses A wrote:
> On Tue, 2014-09-30 at 10:04 +0200, Daniel Vetter wrote:
> > On Mon, Sep 29, 2014 at 03:49:32PM -0700, U. Artie Eoff wrote:
> > > Improper truncated integer division in the scale() function causes
> > > actual_brightness != brightness. This (partial) work-around should be
> > > sufficient for a majority of use-cases, but it is by no means a complete
> > > solution.
> > >
> > > TODO: Determine how best to scale "user" values to "hw" values, and
> > > vice-versa, when the ranges are of different sizes. That would be a
> > > buggy scenario even with this work-around.
> > >
> > > The issue was introduced in the following (v3.17-rc1) commit:
> > >
> > > 6dda730 drm/i915: respect the VBT minimum backlight brightness
> > >
> > > v2: (thanks to Chris Wilson) clarify commit message, use rounded division
> > > macro
> > >
> > > v3: -DIV_ROUND_CLOSEST() fails to build with CONFIG_X86_32=y. (Jani)
> > > -Use DIV_ROUND_CLOSEST_ULL() instead. (Damien)
> > > -v1 and v2 originally authored by Joe Konno.
> > >
> > > Signed-off-by: U. Artie Eoff <ullysses.a.eoff@intel.com>
> >
> > Is there some bug report, internal jira, mailing list reference or similar
> > about this?
> >
> > Note that at least for OTC jira tasks we now want them to be added to
> > commit message with e.g.
> >
> > OTC-Jria: VIZ-4932
> >
>
> Yes, the OTC-Jira task is: VIZ-4395. I'll resubmit with amended commit
> message.
>
> > And I guess I should merge patch 2 before patch 1, right?
>
> No, patch 1 before patch 2.
Oh, I didn't notice that your first add a duplicated version of the macro
and then unify it. That's a bit backwards ...
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
next prev parent reply other threads:[~2014-09-30 16:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-29 22:49 [PATCH 0/2] drm/i915: WA intel_backlight scale math U. Artie Eoff
2014-09-29 22:49 ` [PATCH 1/2 v3] drm/i915: intel_backlight scale() math WA U. Artie Eoff
2014-09-30 8:04 ` Daniel Vetter
2014-09-30 14:58 ` Eoff, Ullysses A
2014-09-30 16:31 ` Daniel Vetter [this message]
2014-09-30 16:52 ` Eoff, Ullysses A
2014-09-30 17:23 ` Daniel Vetter
2014-09-30 21:18 ` Eoff, Ullysses A
2014-10-06 14:14 ` Joe Konno
2014-09-29 22:49 ` [PATCH 2/2] drm/i915: Move DIV_ROUND_CLOSEST_ULL macro to header U. Artie Eoff
2014-10-06 14:15 ` Joe Konno
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