[Nouveau] [PATCH v4 16/37] volt: don't require perfect fit

[Karol Herbst]

if we calculate the voltage in the table right, we get all kinds of values,
which never fit the hardware steps, so we use the closest higher value the
hardware can do.

v3: simplify the implementation

Signed-off-by: Karol Herbst <nouveau at karolherbst.de>
---
 drm/nouveau/nvkm/subdev/volt/base.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drm/nouveau/nvkm/subdev/volt/base.c b/drm/nouveau/nvkm/subdev/volt/base.c
index d72bd4a..028c6e2 100644
--- a/drm/nouveau/nvkm/subdev/volt/base.c
+++ b/drm/nouveau/nvkm/subdev/volt/base.c
@@ -51,18 +51,30 @@ static int
 nvkm_volt_set(struct nvkm_volt *volt, u32 uv)
 {
 	struct nvkm_subdev *subdev = &volt->subdev;
-	int i, ret = -EINVAL;
+	int i, ret = -EINVAL, best_err = uv, best = -1;
 
 	if (volt->func->volt_set)
 		return volt->func->volt_set(volt, uv);
 
 	for (i = 0; i < volt->vid_nr; i++) {
-		if (volt->vid[i].uv == uv) {
-			ret = volt->func->vid_set(volt, volt->vid[i].vid);
-			nvkm_debug(subdev, "set %duv: %d\n", uv, ret);
+		int err = volt->vid[i].uv - uv;
+		if (err < 0 || err > best_err)
+			continue;
+
+		best_err = err;
+		best = i;
+		if (best_err == 0)
 			break;
-		}
 	}
+
+	if (best == -1) {
+		nvkm_error(subdev, "couldn't set %iuv\n", uv);
+		return ret;
+	}
+
+	ret = volt->func->vid_set(volt, volt->vid[best].vid);
+	nvkm_debug(subdev, "set req %duv to %duv: %d\n", uv,
+		   volt->vid[best].uv, ret);
 	return ret;
 }
 
-- 
2.8.1