Re: Fixing the hotplug storm bugs once and for all?

[Eric Anholt <eric@anholt.net>]

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On Mon, 26 Jul 2010 14:06:52 -0400, Andrew Lutomirski <luto@mit.edu> wrote:
> On Mon, Jul 26, 2010 at 1:41 PM, Eric Anholt <eric@anholt.net> wrote:
> > On Sun, 25 Jul 2010 15:29:25 -0400, Andrew Lutomirski <luto@mit.edu> wrote:
> >> For well over a year now, I (and apparently lots of other people) have
> >> had to run patched kernels to avoid crippling hotplug storms.
> >>
> >> As far as I can tell, on my laptop, enabling DPC_HOTPLUG_INT_EN is
> >> safe, but setting either DPB_... or DPD_... (or both) will cause
> >> intermittent hotplug interrupt storms.  (Turning off all three DP
> >> hotplug bits also makes the laptop stable but prevents the DP port
> >> from working.)
> >>
> >> My laptop is a Lenovo X200s with VGA and LVDS on the laptop itself and
> >> DP on the docking port.  If I boot w/o the docking port, I have:
> >>
> >>
> >> General definitions block:
> >>         CRT DDC GMBUS addr: 0x02
> >>         Use ACPI DPMS CRT power states: no
> >>         Skip CRT detect at boot: no
> >>         Use DPMS on AIM devices: yes
> >>         Boot display type: 0x0000
> >>         TV data block present: yes
> >>         Child device info:
> >>                 Device type: 1009 (TV)
> >>                 Signature:
> >>                 AIM offset: 0
> >>                 DVO port: 0x05
> >>         Child device info:
> >>                 Device type: 1022 (LFP)
> >>                 Signature:
> >>                 AIM offset: 52048
> >>                 DVO port: 0x04
> >>         Child device info:
> >>                 Device type: 68c6 (DisplayPort)
> >>                 Signature:
> >>                 AIM offset: 61152
> >>                 DVO port: 0x08
> >>
> >> Maybe it's time we started reading that part of VBIOS to detect which
> >> outputs really exist.  (If that's unsafe, we could add a DMI list.)
> >>
> >> Any thoughts?  It would be nice if 2.6.36 could work without patches.
> >
> > We had patches to not probe outputs unless they were in child dev tables
> > for a while.  The issue with reading child dev tables is that some
> > BIOSes would give you different child dev results depending on whether
> > you were docked or not, so you wouldn't get your DP probed unless you
> > booted docked.
> >
> 
> Do you have a link?  I can try to resurrect them.
> 
> (Can Xorg handle new outputs appearing and disappearing at runtime?
> If not, we could just pretend to create all possible outputs up
> front.)

Yeah, I was figuring set up all outputs, and just always report
disconnected unless it's in the child dev tables.  We can worry about
making a pretty output list later after things *work*.

commit 6207937d4feea000913e8ca23fe20c7744be7847
Author: Zhao Yakui <yakui.zhao@intel.com>
Date:   Wed Jan 6 09:49:31 2010 +0800

    drm/i915: Don't use the child device parsed from VBT to setup HDMI/DP
    
    On some boxes the BIOS will report different child device arrays when
    the system is booted with/without the dock. In such case the HDMI/DP
    port can't be setup correctly.  So revert two commits
    (fc816655236cd9da162356e96e74c7cfb0834d92/
    6e36595a2131e7ed5ee2674be54b2713ba7f0490) that use the child device
    parsed from VBT to setup HDMI/DP.
    
    http://bugzilla.kernel.org/show_bug.cgi?id=14854
    http://bugzilla.kernel.org/show_bug.cgi?id=14860
    
    Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
    Tested-by: Sean Young <sean@mess.org>
    Signed-off-by: Eric Anholt <eric@anholt.net>

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