[Nouveau] [PATCH v2 16/22] 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

Signed-off-by: Karol Herbst <nouveau at karolherbst.de>
---
 drm/nouveau/nvkm/subdev/volt/base.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drm/nouveau/nvkm/subdev/volt/base.c b/drm/nouveau/nvkm/subdev/volt/base.c
index e741383..58738e3 100644
--- a/drm/nouveau/nvkm/subdev/volt/base.c
+++ b/drm/nouveau/nvkm/subdev/volt/base.c
@@ -51,18 +51,37 @@ 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, err, 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);
+		if (i == 0) {
+			best = 0;
+			err = volt->vid[i].uv - uv;
+		} else {
+			int new_err = volt->vid[i].uv - uv;
+			if (abs(new_err) < abs(err)
+			    || (err < 0 && new_err >= 0)) {
+				best = i;
+				err = new_err;
+			}
+		}
+
+		if (err == 0) {
+			ret = volt->func->vid_set(volt, volt->vid[best].vid);
 			nvkm_debug(subdev, "set %duv: %d\n", uv, ret);
 			break;
 		}
 	}
+
+	if (best != -1) {
+		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;
 }
 
-- 
2.7.4