Date: Wed, 28 Jan 2015 01:20:12 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Andrew Wilcox <AWilcox@wilcox-tech.com>, Konstantin Belousov <kib@freebsd.org> Cc: "Ranjan1018 ." <214748mv@gmail.com>, freebsd-current <freebsd-current@freebsd.org> Subject: Re: drm2 regression: backlight adjustment on ivybridge no longer works Message-ID: <CAJ-Vmon1ck2QXXn-=_PAwdFudhRtgcQKCK-V454Ctn9aQs-cpw@mail.gmail.com> In-Reply-To: <CAJ-Vmom3gLa_2EoviL0Ck2B36Bpa-3P58%2BUp5rsLFaH-NS4ExQ@mail.gmail.com> References: <CAJ-VmomfBrBN6HVBq5FoRf1nRqvrhiDOw6RHjfs13j-9cqi1vg@mail.gmail.com> <CACyC=qYMT3VFx4GxypJ6F61pKSaxE0JKBK%2BudDMPSh4_ASAi6w@mail.gmail.com> <000e01d039fb$d5959930$80c0cb90$@Wilcox-Tech.com> <CACyC=qZeG8L%2BbZu=RacU_rdNVTFhyCFH2A%2BdNw71%2B09cZ20VgA@mail.gmail.com> <009501d03acb$4f380d70$eda82850$@Wilcox-Tech.com> <CAJ-Vmokph=BHH895uHxQh=dHPfb5_ik4MZrq8sOGrd0AtPzymQ@mail.gmail.com> <CAJ-Vmom3gLa_2EoviL0Ck2B36Bpa-3P58%2BUp5rsLFaH-NS4ExQ@mail.gmail.com>
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and the commit from linux:
commit 7aa1e7f06d6ea1bce3b27630d50769d13da28b1a
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Wed Jun 27 16:43:36 2012 +0200
Revert "drm/i915: allow PCH PWM override on IVB"
This reverts commit f82cfb6bcda164ef3a66b8c3fc549b1f9bdd09ad.
This breaks the backlight controls on my IVB asus zenbook with an eDP
panel.
I guess the right fix would be to read this bit and use either the pch
or the cpu register to frob the backlight values. But that is stuff
for -next.
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
On 28 January 2015 at 01:11, Adrian Chadd <adrian@freebsd.org> wrote:
> ugh, so because i can't sleep, I read the Linux i915 history for
> backlight changes.
>
> Turns out if I disable bit 30 in ivb_pch_pwm_override() to register
> BLC_PWM_PCH_CTL1, the acpi video setting works. The keyboard settings
> still don't, but I'll worry about that later.
>
> Bit 30 in the linux drm code is:
>
> #define BLM_PCH_OVERRIDE_ENABLE (1 << 30)
>
> The linux dri code doesn't set that for ivybridge - only for broadwell.
>
> (also, the linux driver has POSTING_READ() which I'm guessing is to
> ensure things made it out to the device and have been flushed before
> doing another IO operation.)
>
> I have my (via sysctl) panel backlight control working again.
>
>
>
> -adrian
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