Date: Wed, 28 Jan 2015 01:11:19 -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-Vmom3gLa_2EoviL0Ck2B36Bpa-3P58%2BUp5rsLFaH-NS4ExQ@mail.gmail.com> In-Reply-To: <CAJ-Vmokph=BHH895uHxQh=dHPfb5_ik4MZrq8sOGrd0AtPzymQ@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>
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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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