drm/nouveau: add voltage workaround for buggy vbioses

index 4fe883c..624cbd1 100644
@@ -251,6 +251,7 @@ static void
 nouveau_perf_voltage(struct drm_device *dev, struct nouveau_pm_level *perflvl)
 {
 	struct nouveau_drm *drm = nouveau_drm(dev);
+	struct nouveau_pm_voltage *volt = &nouveau_pm(dev)->voltage;
 	struct bit_entry P;
 	u8 *vmap;
 	int id;

@@ -287,6 +288,20 @@ nouveau_perf_voltage(struct drm_device *dev, struct nouveau_pm_level *perflvl)
 		perflvl->volt_min = ROM32(vmap[0]);
 		perflvl->volt_max = ROM32(vmap[4]);
 	}
+
+	/* Adjust for buggy bioses */
+	if (!volt->step_uv || !volt->step_ofs)
+		return;
+
+	if (perflvl->volt_min % volt->step_uv != volt->step_ofs) {
+		perflvl->volt_min -= perflvl->volt_min % volt->step_uv;
+		perflvl->volt_min += volt->step_ofs;
+	}
+
+	if (perflvl->volt_max % volt->step_uv != volt->step_ofs) {
+		perflvl->volt_max -= perflvl->volt_max % volt->step_uv;
+		perflvl->volt_max += volt->step_ofs;
+	}
 }
 
 void

index 73b789c..967c27c 100644
@@ -40,6 +40,7 @@ struct nouveau_pm_voltage {
 
 	struct nouveau_pm_voltage_level *level;
 	int nr_level;
+	u16 step_uv, step_ofs;
 };
 
 /* Exclusive upper limits */

index 9976414..c8d0c00 100644
@@ -236,6 +236,9 @@ nouveau_volt_init(struct drm_device *dev)
 			voltage->level[vid].vid = vid;
 			volt_uv += step_uv;
 		}
+		voltage->step_uv = step_uv >= 0 ? step_uv : -step_uv;
+		if (step_uv)
+			voltage->step_ofs = volt_uv % voltage->step_uv;
 	}
 
 	voltage->supported = true;