drm/nouveau: use static vidshift of 2 on volt 0x30 tables

Explanation is in the commit.  If anyone has an example of where this is
*not* the case, please report it!

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_volt.c b/drivers/gpu/drm/nouveau/nouveau_volt.c
index 04fdc00a67d..75e872741d9 100644
--- a/drivers/gpu/drm/nouveau/nouveau_volt.c
+++ b/drivers/gpu/drm/nouveau/nouveau_volt.c
@@ -159,8 +159,16 @@ nouveau_volt_init(struct drm_device *dev)
                 headerlen = volt[1];
                 recordlen = volt[2];
                 entries   = volt[3];
-                vidshift  = hweight8(volt[5]);
                 vidmask   = volt[4];
+                /* no longer certain what volt[5] is, if it's related to
+                 * the vid shift then it's definitely not a function of
+                 * how many bits are set.
+                 *
+                 * after looking at a number of nva3+ vbios images, they
+                 * all seem likely to have a static shift of 2.. lets
+                 * go with that for now until proven otherwise.
+                 */
+                vidshift  = 2;
                 break;
         default:
                 NV_WARN(dev, "voltage table 0x%02x unknown\n", volt[0]);