On 30/09/2014 08:47, Andriy Gapon wrote:
> I think that currently vt_suspend / vt_resume are called at quite unsuitable
> times.  For example, vt_suspend performs a vt switch which requires 
> cooperation
> from an X server, but that could be problematic given that some devices may
> already be suspended.
> I believe that it is better to do what sc(4) does and use power_suspend /
> power_resume event handlers instead of device_suspend / device_resume methods.
> power_suspend event is posted when a kernel has not entered any special state 
> yet.
> What do you think?

So, I am now using the following patch and suspend/resume works 100% reliable
for me, whereas previously there was a quite significant chance that the video
subsystem would be in a very confused state after resuming.

For example there could be an endless stream of error message and the screen
would be frozen:
drmn0: error: couldn't schedule ib
error: [drm:pid1492:radeon_cs_ib_chunk] *ERROR* Failed to schedule IB !

Or there could be an endless GPU reset loop in the radeon driver:
drmn0: error: GPU lockup CP stall for more than 10000msec
drmn0: warning: GPU lockup (waiting for 0x0000000000269544 last fence id
error: [drm:pid1492:r600_ib_test] *ERROR* radeon: fence wait failed (-11).
error: [drm:pid1492:radeon_ib_ring_tests] *ERROR* radeon: failed testing IB on
GFX ring (-11).
drmn0: error: ib ring test failed (-11).
drmn0: info: GPU softreset: 0x00000003

The patch (I am not sure if fbd_attach is the right place to register the event

diff --git a/sys/dev/fb/fbd.c b/sys/dev/fb/fbd.c
index ff2488d..923292a 100644
--- a/sys/dev/fb/fbd.c
+++ b/sys/dev/fb/fbd.c
@@ -316,6 +316,11 @@ fbd_attach(device_t dev)
                return (ENXIO);
        err = fbd_register(sc->sc_info);

+       EVENTHANDLER_REGISTER(power_suspend, vt_fb_suspend, NULL,
+                             EVENTHANDLER_PRI_ANY);
+       EVENTHANDLER_REGISTER(power_resume, vt_fb_resume, NULL,
+                             EVENTHANDLER_PRI_ANY);
        return (err);

@@ -332,22 +337,6 @@ fbd_detach(device_t dev)
        return (err);

-static int
-fbd_suspend(device_t dev)
-       vt_fb_suspend();
-       return (bus_generic_suspend(dev));
-static int
-fbd_resume(device_t dev)
-       vt_fb_resume();
-       return (bus_generic_resume(dev));
 static device_method_t fbd_methods[] = {
        /* Device interface */
        DEVMETHOD(device_probe,         fbd_probe),
@@ -355,8 +344,6 @@ static device_method_t fbd_methods[] = {
        DEVMETHOD(device_detach,        fbd_detach),

        DEVMETHOD(device_shutdown,      bus_generic_shutdown),
-       DEVMETHOD(device_suspend,       fbd_suspend),
-       DEVMETHOD(device_resume,        fbd_resume),

        { 0, 0 }

Andriy Gapon
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