drm/nouveau/fb: restore init() for ramgp102

commit 6db9df4 upstream.

init() was removed from ramgp102 when reworking the memory detection, as
it was thought that the code was only necessary when the driver performs
mclk changes, which nouveau doesn't support on pascal.

However, it turns out that we still need to execute this on some GPUs to
restore settings after DEVINIT, so revert to the original behaviour.

v2: fix tags in commit message, cc stable

Closes: https://gitlab.freedesktop.org/drm/nouveau/-/issues/319
Fixes: 2c0c15a ("drm/nouveau/fb/gp102-ga100: switch to simpler vram size detection method")
Cc: stable@vger.kernel.org # 6.6+
Signed-off-by: Ben Skeggs <bskeggs@nvidia.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240904232418.8590-1-bskeggs@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ben Skeggs

drivers/gpu/drm/nouveau/nvkm/subdev/fb/ram.h

@@ -46,6 +46,8 @@ u32 gm107_ram_probe_fbp(const struct nvkm_ram_func *,
 u32 gm200_ram_probe_fbp_amount(const struct nvkm_ram_func *, u32,
 			       struct nvkm_device *, int, int *);
 
+int gp100_ram_init(struct nvkm_ram *);
+
 /* RAM type-specific MR calculation routines */
 int nvkm_sddr2_calc(struct nvkm_ram *);
 int nvkm_sddr3_calc(struct nvkm_ram *);

drivers/gpu/drm/nouveau/nvkm/subdev/fb/ramgp100.c

@@ -27,7 +27,7 @@
 #include <subdev/bios/init.h>
 #include <subdev/bios/rammap.h>
 
-static int
+int
 gp100_ram_init(struct nvkm_ram *ram)
 {
 	struct nvkm_subdev *subdev = &ram->fb->subdev;

drivers/gpu/drm/nouveau/nvkm/subdev/fb/ramgp102.c

@@ -5,6 +5,7 @@
 
 static const struct nvkm_ram_func
 gp102_ram = {
+	.init = gp100_ram_init,
 };
 
 int