Radeon AGP suspend/resume support
nate at root.org
Sat Oct 9 20:02:23 PDT 2004
Bruce M Simpson wrote:
> On Fri, Oct 08, 2004 at 03:27:58AM -0700, Bruce M Simpson wrote:
>>Ok. Well some initial research suggests that many of the userland pieces are
>>already there in xorg 6.7.0, after some rummaging around in the source:
> Actually the problem is worse than that, from what I can see. There is a
> module in the xorg/Xfree86 tree called bsd_apm.c. This is meant to poll
> the /dev/apm device on the BSDs for suspend/resume event notifications
> coming from the APM BIOS.
> There are two problems with this:
> 1) This uses a NetBSD specific interface, which, whilst broadly similar
> to FreeBSD's apm support, is not ABI compatible with ours.
I've made a patch for this (attached) that uses a set of compat defines.
> 2) The ACPI apm shim does not dispatch such events. They are only
> dispatched within the system if 'real' BIOS APM support is in the
> kernel. This cannot co-exist with ACPI. Furthermore they are only
> announced on the /dev/apmctl device; there are some comments in the
> code to this effect.
Since the comments claim NetBSD dispatches these on /dev/apmctl but the
bsd_apm.c code only uses /dev/apm, either NetBSD doesn't actually work
or it also dispatches the events to /dev/apm.
> So *no* suspend/resume support ever actually gets called, for any userland
> driver in the X tree, on FreeBSD. It seems X needs to be re-educated about
> how FreeBSD suspends and resumes. It may well be more appropriate to rewrite
> this module entirely from scratch for use with ACPI.
I forgot to mention before, this isn't actually true. We call the VTY
switch code in user mode to switch to a tty before suspending and switch
back to X on resume. This has the same effect as a suspend/resume in
most cases since the driver needs to restore the video mode. I agree
that it's better though to explicitly work with X's suspend/resume
support. Can Eric or someone more familiar with X comment on how
bsd_apm.c and the like is actually used in practice? I'm not sure which
events X actually uses, whether it needs to block, etc.
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