On Wed, 28 Aug 2002, Egbert Eich wrote:
>Date: Wed, 28 Aug 2002 12:33:02 +0200 (MEST)
>From: Egbert Eich <[EMAIL PROTECTED]>
>To: [EMAIL PROTECTED]
>Reply-To: [EMAIL PROTECTED]
>Content-Type: text/plain; charset=us-ascii
>Subject: Re: Re: [Dri-devel] Radeon switch to VT and back X freeze
> POSSIBLE FIX
>
>Carlos O'Donell writes:
> > dri-devel,
> >
> > Just coming out of the woodwork to post a few ideas...
> >
> > It would be interesting to see if bus mastering gets disabled
> > on any other PCI devices?
> >
> > Anyone have a PCI logic analyzer? :)
> >
> > Would it be the norm to expect that a VT switch (going through
> > though the BIOS) would cause a BM disable in order to cancel
> > pending transactions (similar to soft reset)?
>
>A VT switch restores the PCI state to the situation when the
>Xserver was started. Therefore if BM was enabled when X was
>started (ie by the BIOS at boot time) it will remain enabled.
>Otherwise it will be disabled and will remain disabled until the
>driver explicitely reenables it.
>At the time this decision was made it sounded like the most reasonable
>approach to leave as little as possible behind when terminating/VT
>switching X.
I'm pretty sure some of the X drivers still force busmastering on
when it is needed and found off during startup to get around BIOS
bugs in some laptop computers that do not enable BM but require
it.
In the Radeon VT switch case however this is a different issue.
What is happening, is:
Start computer, do not start X: Busmastering is enabled
Start up X: Busmastering still enabled
VTswitch: Now in console, Busmaster is disabled
VTswitch back to X: Busmastering disabled still - BOOM.
Why busmastering is getting disabled during VTswitch is probably
something that should be determined. Why it only happens for
some people, and the busmaster patch fixes it is probably just a
hack around the real problem.
Anyone feel like figuring out the root cause? ;o)
--
Mike A. Harris
I'd offer to change your mind for you, but I don't have a fresh diaper.
-- Leah to pro-spammer in news.admin.net-abuse.email
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