drm/nouveau/therm: don't attempt fan control where PMU is already managing it

There's already a condition in place which attempts to detect this, but
since we've begun to require a PMU subdev even on boards where we don't
load a custom FW, it's become inaccurate.

This will prevent unnecessarily running a periodic fan update thread on
GP100 and newer, where we don't yet override the default PMU FW.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/subdev/pmu.h

@@ -30,6 +30,7 @@ struct nvkm_pmu {
 int nvkm_pmu_send(struct nvkm_pmu *, u32 reply[2], u32 process,
 		  u32 message, u32 data0, u32 data1);
 void nvkm_pmu_pgob(struct nvkm_pmu *, bool enable);
+bool nvkm_pmu_fan_controlled(struct nvkm_device *);
 
 int gt215_pmu_new(struct nvkm_device *, int, struct nvkm_pmu **);
 int gf100_pmu_new(struct nvkm_device *, int, struct nvkm_pmu **);

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

@@ -26,6 +26,24 @@
 #include <core/msgqueue.h>
 #include <subdev/timer.h>
 
+bool
+nvkm_pmu_fan_controlled(struct nvkm_device *device)
+{
+	struct nvkm_pmu *pmu = device->pmu;
+
+	/* Internal PMU FW does not currently control fans in any way,
+	 * allow SW control of fans instead.
+	 */
+	if (pmu && pmu->func->code.size)
+		return false;
+
+	/* Default (board-loaded, or VBIOS PMU/PREOS) PMU FW on Fermi
+	 * and newer automatically control the fan speed, which would
+	 * interfere with SW control.
+	 */
+	return (device->chipset >= 0xc0);
+}
+
 void
 nvkm_pmu_pgob(struct nvkm_pmu *pmu, bool enable)
 {

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

@@ -21,9 +21,11 @@
  *
  * Authors: Martin Peres
  */
-#include <nvkm/core/option.h>
 #include "priv.h"
 
+#include <core/option.h>
+#include <subdev/pmu.h>
+
 int
 nvkm_therm_temp_get(struct nvkm_therm *therm)
 {
@@ -192,8 +194,7 @@ nvkm_therm_fan_mode(struct nvkm_therm *therm, int mode)
 
 	/* The default PPWR ucode on fermi interferes with fan management */
 	if ((mode >= ARRAY_SIZE(name)) ||
-	    (mode != NVKM_THERM_CTRL_NONE && device->card_type >= NV_C0 &&
-	     !device->pmu))
+	    (mode != NVKM_THERM_CTRL_NONE && nvkm_pmu_fan_controlled(device)))
 		return -EINVAL;
 
 	/* do not allow automatic fan management if the thermal sensor is