nouveau/gsp: add a 50ms delay between fbsr and driver unload rpcs

This fixes a bunch of command hangs after runtime suspend/resume.

This fixes a regression caused by code movement in the commit below,
the commit seems to just change timings enough to cause this to happen
now, and adding the sleep seems to avoid it.

I've spent some time trying to root cause it to no great avail,
it seems like a bug on the firmware side, but it could be a bug
in our rpc handling that I can't find.

Either way, we should land the workaround to fix the problem,
while we continue to work out the root cause.

Signed-off-by: Dave Airlie <[email protected]>
Cc: Ben Skeggs <[email protected]>
Cc: Danilo Krummrich <[email protected]>
Fixes: c21b039 ("drm/nouveau/gsp: add hals for fbsr.suspend/resume()")
Signed-off-by: Danilo Krummrich <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: airlied

drivers/gpu/drm/nouveau/nvkm/subdev/gsp/rm/r535/gsp.c

@@ -1744,6 +1744,13 @@ r535_gsp_fini(struct nvkm_gsp *gsp, bool suspend)
 			nvkm_gsp_sg_free(gsp->subdev.device, &gsp->sr.sgt);
 			return ret;
 		}
+
+		/*
+		 * TODO: Debug the GSP firmware / RPC handling to find out why
+		 * without this Turing (but none of the other architectures)
+		 * ends up resetting all channels after resume.
+		 */
+		msleep(50);
 	}
 
 	ret = r535_gsp_rpc_unloading_guest_driver(gsp, suspend);