drm/nouveau/gr/gp107,gp108: implement workaround for HW hanging during init

[ Upstream commit 028a12f5aa829b4ba6ac011530b815eda4960e89 ]

Certain boards with GP107/GP108 chipsets hang (often, but randomly) for
unknown reasons during GR initialisation.

The first tell-tale symptom of this issue is:

nouveau 0000:01:00.0: bus: MMIO read of 00000000 FAULT at 409800 [ TIMEOUT ]

appearing in dmesg, likely followed by many other failures being logged.

Karol found this WAR for the issue a while back, but efforts to isolate
the root cause and proper fix have not yielded success so far.  I've
modified the original patch to include a few more details, limit it to
GP107/GP108 by default, and added a config option to override this choice.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/gr/gf100.c b/drivers/gpu/drm/nouveau/nvkm/engine/gr/gf100.c
index c578deb..c71606a 100644 (file)
--- a/drivers/gpu/drm/nouveau/nvkm/engine/gr/gf100.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/gr/gf100.c
@@ -1988,8 +1988,34 @@ gf100_gr_init_(struct nvkm_gr *base)
 {
        struct gf100_gr *gr = gf100_gr(base);
        struct nvkm_subdev *subdev = &base->engine.subdev;
+       struct nvkm_device *device = subdev->device;
+       bool reset = device->chipset == 0x137 || device->chipset == 0x138;
        u32 ret;
 
+       /* On certain GP107/GP108 boards, we trigger a weird issue where
+        * GR will stop responding to PRI accesses after we've asked the
+        * SEC2 RTOS to boot the GR falcons.  This happens with far more
+        * frequency when cold-booting a board (ie. returning from D3).
+        *
+        * The root cause for this is not known and has proven difficult
+        * to isolate, with many avenues being dead-ends.
+        *
+        * A workaround was discovered by Karol, whereby putting GR into
+        * reset for an extended period right before initialisation
+        * prevents the problem from occuring.
+        *
+        * XXX: As RM does not require any such workaround, this is more
+        *      of a hack than a true fix.
+        */
+       reset = nvkm_boolopt(device->cfgopt, "NvGrResetWar", reset);
+       if (reset) {
+               nvkm_mask(device, 0x000200, 0x00001000, 0x00000000);
+               nvkm_rd32(device, 0x000200);
+               msleep(50);
+               nvkm_mask(device, 0x000200, 0x00001000, 0x00001000);
+               nvkm_rd32(device, 0x000200);
+       }
+
        nvkm_pmu_pgob(gr->base.engine.subdev.device->pmu, false);
 
        ret = nvkm_falcon_get(gr->fecs.falcon, subdev);