Petr Vandrovec wrote:
Hello Jeff,
I'm using second patch below for couple of months to get MSI on all
devices present on my notebook which are MSI capable (except IDE - notebook
uses IDE in legacy mode and seems unhappy with transition to native MSI-based
mode; maybe I could try do the job with libata now when I switched; and VGA, I
do not use dri...). All worked nicely until last sync, when I noticed that my
USB devices suddenly stopped working (it took me few weeks as I do not use USB
regulary).
After poking around I've found that problem is that at least ATI USB-HCDs
apply INTX enable even for MSI, despite warning in the PCI specification that
it should apply only to MSI (actually I have feeling that on these USB devices
disabling INTX in MSI mode drives their INTA# line active as when ohci1394
module got loaded kernel complained about interrupt being continuously
activated for no good reason (TI's 7421 is one of few MSI-incapable devices
in my box).
So my question is - what is real reason for disabling INTX when in MSI mode?
According to PCI spec it should not be needed, and it hurts at least chips
listed below:
00:13.0 0c03: 1002:4374 USB Controller: ATI Technologies Inc IXP SB400 USB Host
Controller
00:13.1 0c03: 1002:4375 USB Controller: ATI Technologies Inc IXP SB400 USB Host
Controller
00:13.2 0c03: 1002:4373 USB Controller: ATI Technologies Inc IXP SB400 USB2 Host Controller
I believe that these devices from same vendor accept disabling INTX while in MSI
fine (I did not notice problems with them even with INTX disabling code in
msi.c):
00:14.5 0401: 1002:4370 (rev 02) Multimedia audio controller: ATI Technologies
Inc IXP SB400 AC'97 Audio Controller (rev 02)
00:14.6 0703: 1002:4378 (rev 02) Modem: ATI Technologies Inc ATI SB400 - AC'97
Modem Controller (rev 02)
None of devices in the box assert INTX while in MSI even if INTX is enabled.
So I'd like to see first patch below accepted. If there are some devices which
require INTX disabling, then apparently decision whether to disable it or no
has to be moved to device drivers, or some blacklist/whitelist must be
created...
Linus' original position on this issue was that any devices which broke
from disabling INTX when going into MSI mode were just broken and we
should blacklist MSI entirely for these devices. The reason this change
went in is that some devices don't automatically disable INTX when MSI
is turned on (somewhat contrary to the PCI spec apparently).
This whole issue might need to be reopened though..
--
Robert Hancock Saskatoon, SK, Canada
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