Radeon AGP suspend/resume support

Nate Lawson 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:
>>	http://www.spinics.net/lists/xf-xpert/msg04368.html
> 
> 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.

-- 
Nate


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