drm/nouveau: Don't disable polling in fallback mode

[ Upstream commit 11878006 ]

When a fan is controlled via linear fallback without cstate, we
shouldn't stop polling.  Otherwise it won't be adjusted again and
keeps running at an initial crazy pace.

Fixes: 800efb4c ("drm/nouveau/drm/therm/fan: add a fallback if no fan control is specified in the vbios")
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1103356
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107447Reported-by: Thomas Blume <thomas.blume@suse.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Martin Peres <martin.peres@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/gpu/drm/nouveau/nvkm/subdev/therm/base.c

@@ -131,11 +131,12 @@ nvkm_therm_update(struct nvkm_therm *therm, int mode)
 			duty = nvkm_therm_update_linear(therm);
 			break;
 		case NVBIOS_THERM_FAN_OTHER:
-			if (therm->cstate)
+			if (therm->cstate) {
 				duty = therm->cstate;
-			else
-				duty = nvkm_therm_update_linear_fallback(therm);
 				poll = false;
+			} else {
+				duty = nvkm_therm_update_linear_fallback(therm);
+			}
 			break;
 		}
 		immd = false;