drm/nouveau/volt: save the voltage range we are able to set

We shouldn't set voltages below the min or above the max voltage the gpu is
able to set, so save the range for future lookups.
Signed-off-by: Karol Herbst <karolherbst@gmail.de>
Reviewed-by: Martin Peres <martin.peres@free.fr>
Tested-by: Pierre Moreau <pierre.morrow@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

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

@@ -12,6 +12,9 @@ struct nvkm_volt {
 		u32 uv;
 		u8 vid;
 	} vid[256];
+
+	u32 max_uv;
+	u32 min_uv;
 };
 
 int nvkm_volt_get(struct nvkm_volt *);

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

@@ -120,6 +120,8 @@ nvkm_volt_parse_bios(struct nvkm_bios *bios, struct nvkm_volt *volt)
 
 	data = nvbios_volt_parse(bios, &ver, &hdr, &cnt, &len, &info);
 	if (data && info.vidmask && info.base && info.step) {
+		volt->min_uv = info.min;
+		volt->max_uv = info.max;
 		for (i = 0; i < info.vidmask + 1; i++) {
 			if (info.base >= info.min &&
 				info.base <= info.max) {
@@ -131,6 +133,8 @@ nvkm_volt_parse_bios(struct nvkm_bios *bios, struct nvkm_volt *volt)
 		}
 		volt->vid_mask = info.vidmask;
 	} else if (data && info.vidmask) {
+		volt->min_uv = 0xffffffff;
+		volt->max_uv = 0;
 		for (i = 0; i < cnt; i++) {
 			data = nvbios_volt_entry_parse(bios, i, &ver, &hdr,
 						       &ivid);
@@ -138,9 +142,14 @@ nvkm_volt_parse_bios(struct nvkm_bios *bios, struct nvkm_volt *volt)
 				volt->vid[volt->vid_nr].uv = ivid.voltage;
 				volt->vid[volt->vid_nr].vid = ivid.vid;
 				volt->vid_nr++;
+				volt->min_uv = min(volt->min_uv, ivid.voltage);
+				volt->max_uv = max(volt->max_uv, ivid.voltage);
 			}
 		}
 		volt->vid_mask = info.vidmask;
+	} else if (data && info.type == NVBIOS_VOLT_PWM) {
+		volt->min_uv = info.base;
+		volt->max_uv = info.base + info.pwm_range;
 	}
 }
 
@@ -181,8 +190,11 @@ nvkm_volt_ctor(const struct nvkm_volt_func *func, struct nvkm_device *device,
 	volt->func = func;
 
 	/* Assuming the non-bios device should build the voltage table later */
-	if (bios)
+	if (bios) {
 		nvkm_volt_parse_bios(bios, volt);
+		nvkm_debug(&volt->subdev, "min: %iuv max: %iuv\n",
+			   volt->min_uv, volt->max_uv);
+	}
 
 	if (volt->vid_nr) {
 		for (i = 0; i < volt->vid_nr; i++) {