tree efd038c8a66706dac953371295fea68d1bf4212e
parent bbb8c3d8820893694a3567716adb3b6f6ba2b7d0
author Ben Skeggs <bskeggs@redhat.com> 1262743202 +1000
committer Ben Skeggs <bskeggs@redhat.com> 1263164802 +1000

drm/nv50: prevent a possible ctxprog hang

The below is mainly an educated guess at what's going on, docs would
sure be handy...  NVIDIA? :P

It appears it's possible for a ctxprog to run even while a GPU exception
is pending.  The GF8 and up ctxprogs appear to have a small snippet of
code which detects this, and stalls the ctxprog until it's been handled,
which essentially looks like:

	if (r2 & 0x00008000) {
		r0 |= 0x80000000;
		while (r0 & 0x80000000) {}
	}

I don't know of any way that flag would get cleared unless the driver
intervenes (and indeed, in the cases I've seen the hang, nothing steps
in to automagically clear it for us).  This patch causes the driver to
clear the flag during the PGRAPH IRQ handler.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>