Re: [PATCH 1/1] Revert "drm/i915: drop i915_ prefix from enable_rc6, enable_fbc, enable_ppgtt parameters"

[Amit Shah <amit.shah@redhat.com>]

On (Thu) 17 Jul 2014 [09:35:20], Daniel Vetter wrote:
> On Wed, Jul 16, 2014 at 9:54 PM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> > Sorry for the top post, I'm on the road..
> >
> > In wondering if we couldn't just keep both the old an the new names and have
> > them both point at the same variable? Remove the description for the old
> > name, but keep it working?
> 
> I'm really surprised here ... We have rc6 enabled by default
> everywhere, and all the additional rc6 levels that users try to enable
> are known to hard-hang machines.

I haven't had this problem on my hardware (ThinkPad T420s, lspci
below) for a few kernel versions.  I think I added the enable_rc6=
setting back from the time the deeper states were enabled and then
reverted for SandyBridge.

Nevertheless, with the current state, RC6p and RC6pp states are not
used.

> I actually have plans to taint the
> kernel if you set any of them since I'm fed up with the random crash
> reports. Same for fbc, even more so or the ppgtt knob. My stance is
> that if you know about these knobs you _really_ should know the driver
> to its depths and so also be able to follow module parameter
> renamings.

I also remember there being bugzillas about power consumption, and
using this setting was recommended (for Fedora, I think).  I know
a few people are using this setting.

> > On Jul 16, 2014 8:34 AM, "Amit Shah" <amit.shah@redhat.com> wrote:
> >>
> >> This reverts commit 3adee7a7976012a20f1d3b5a529a3c105e29fef1.
> >>
> >> After upgrading to v3.15, my laptop's battery started draining quite
> >> fast.  Powertop pointed to the deep RC6 states not being used.  The
> >> kernel param I had put to enable them had stopped working the way it
> >> used to; so I disagree with the 'not maintaing ABI' part of the param
> >> name change.
> >>
> >> However weird the names may be, they're in active use and changing them
> >> only causes pain for users.  This also isn't advertised (marked
> >> deprecated, big warning shown, etc.), so just reverting now.
> >>
> >> CC: Daniel Vetter <daniel.vetter@ffwll.ch>
> >> CC: Jani Nikula <jani.nikula@linux.intel.com>
> >> CC: David Airlie <airlied@linux.ie>
> >> CC: <stable@vger.kernel.org> # v3.15+
> >> Signed-off-by: Amit Shah <amit.shah@redhat.com>
> 
> Anyway we need to figure out what went wrong here. Please share your
> exact kernelcmdline and lspci -nn. Also stats for before/after from
> powertop when idle please.

Powertop stats for idle are a little difficult -- since this is my
primary laptop.

BOOT_IMAGE=/vmlinuz-3.15.4-200.fc20.x86_64 root=/dev/mapper/luks-3aff2acf-737d-4002-b644-15f599d09a18 ro rd.lvm.lv=fedora_grmbl/00 rd.lvm.lv=fedora_grmbl/01 vconsole.font=latarcyrheb-sun16 rd.luks.uuid=luks-0934d354-5b07-4e91-a699-9bfc57e76fdc rd.luks.uuid=luks-3aff2acf-737d-4002-b644-15f599d09a18 rhgb quiet slub_debug=- i915.i915_enable_rc6=7 LANG=en_IN.UTF-8

00:00.0 Host bridge [0600]: Intel Corporation 2nd Generation Core Processor Family DRAM Controller [8086:0104] (rev 09)
00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0126] (rev 09)
00:16.0 Communication controller [0780]: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 [8086:1c3a] (rev 04)
00:19.0 Ethernet controller [0200]: Intel Corporation 82579LM Gigabit Network Connection [8086:1502] (rev 04)
00:1a.0 USB controller [0c03]: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 [8086:1c2d] (rev 04)
00:1b.0 Audio device [0403]: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller [8086:1c20] (rev 04)
00:1c.0 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 [8086:1c10] (rev b4)
00:1c.1 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 [8086:1c12] (rev b4)
00:1c.3 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 [8086:1c16] (rev b4)
00:1c.4 PCI bridge [0604]: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 5 [8086:1c18] (rev b4)
00:1d.0 USB controller [0c03]: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 [8086:1c26] (rev 04)
00:1f.0 ISA bridge [0601]: Intel Corporation QM67 Express Chipset Family LPC Controller [8086:1c4f] (rev 04)
00:1f.2 SATA controller [0106]: Intel Corporation 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller [8086:1c03] (rev 04)
00:1f.3 SMBus [0c05]: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller [8086:1c22] (rev 04)
03:00.0 Network controller [0280]: Intel Corporation Centrino Advanced-N 6205 [Taylor Peak] [8086:0085] (rev 34)
05:00.0 SD Host controller [0805]: Ricoh Co Ltd MMC/SD Host Controller [1180:e822] (rev 07)
0d:00.0 USB controller [0c03]: NEC Corporation uPD720200 USB 3.0 Host Controller [1033:0194] (rev 04)


Thanks,
		Amit