[Intel-gfx] Fixing the hotplug storm bugs once and for all?

Andrew Lutomirski luto at mit.edu
Sun Jul 25 21:29:25 CEST 2010

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)
                AIM offset: 0
                DVO port: 0x05
        Child device info:
                Device type: 1022 (LFP)
                AIM offset: 52048
                DVO port: 0x04
        Child device info:
                Device type: 68c6 (DisplayPort)
                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.


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