drm/nouveau/clk: Don't create cstates with voltages higher than what the gpu can do

nvkm_volt_map_min is a copy of nvkm_volt_map, which always returns the
lowest possible voltage for a cstate.

nvkm_volt_map will get a temperature parameter there later and also fix
the voltage calculation, so that this functions will be completly
different later.

Signed-off-by: Karol Herbst <karolherbst@gmail.com>
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

@@ -17,6 +17,7 @@ struct nvkm_volt {
 	u32 min_uv;
 };
 
+int nvkm_volt_map_min(struct nvkm_volt *volt, u8 id);
 int nvkm_volt_get(struct nvkm_volt *);
 int nvkm_volt_set_id(struct nvkm_volt *, u8 id, int condition);
 

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

@@ -138,6 +138,7 @@ static int
 nvkm_cstate_new(struct nvkm_clk *clk, int idx, struct nvkm_pstate *pstate)
 {
 	struct nvkm_bios *bios = clk->subdev.device->bios;
+	struct nvkm_volt *volt = clk->subdev.device->volt;
 	const struct nvkm_domain *domain = clk->domains;
 	struct nvkm_cstate *cstate = NULL;
 	struct nvbios_cstepX cstepX;
@@ -148,6 +149,9 @@ nvkm_cstate_new(struct nvkm_clk *clk, int idx, struct nvkm_pstate *pstate)
 	if (!data)
 		return -ENOENT;
 
+	if (volt && nvkm_volt_map_min(volt, cstepX.voltage) > volt->max_uv)
+		return -EINVAL;
+
 	cstate = kzalloc(sizeof(*cstate), GFP_KERNEL);
 	if (!cstate)
 		return -ENOMEM;

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

@@ -65,6 +65,28 @@ nvkm_volt_set(struct nvkm_volt *volt, u32 uv)
 	return ret;
 }
 
+int
+nvkm_volt_map_min(struct nvkm_volt *volt, u8 id)
+{
+	struct nvkm_bios *bios = volt->subdev.device->bios;
+	struct nvbios_vmap_entry info;
+	u8  ver, len;
+	u16 vmap;
+
+	vmap = nvbios_vmap_entry_parse(bios, id, &ver, &len, &info);
+	if (vmap) {
+		if (info.link != 0xff) {
+			int ret = nvkm_volt_map_min(volt, info.link);
+			if (ret < 0)
+				return ret;
+			info.min += ret;
+		}
+		return info.min;
+	}
+
+	return id ? id * 10000 : -ENODEV;
+}
+
 static int
 nvkm_volt_map(struct nvkm_volt *volt, u8 id)
 {