[PATCH] drm/mgag200: Fix value in <VBLKSTR> register

[Wakko Warner]

Thomas Zimmermann wrote:
> Fix an off-by-one error when setting the vblanking start in
> <VBLKSTR>. Commit d6460bd52c27 ("drm/mgag200: Add dedicated
> variables for blanking fields") switched the value from
> crtc_vdisplay to crtc_vblank_start, which DRM helpers copy
> from the former. The commit missed to subtract one though.

Applied to 6.14.2.  BMC and external monitor works as expected.

Thank you.

> Reported-by: Wakko Warner <wakko at animx.eu.org>
> Closes: https://lore.kernel.org/dri-devel/CAMwc25rKPKooaSp85zDq2eh-9q4UPZD=RqSDBRp1fAagDnmRmA@mail.gmail.com/
> Reported-by: ???????????? <afmerlord at gmail.com>
> Closes: https://lore.kernel.org/all/5b193b75-40b1-4342-a16a-ae9fc62f245a@gmail.com/
> Closes: https://bbs.archlinux.org/viewtopic.php?id=303819
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> Fixes: d6460bd52c27 ("drm/mgag200: Add dedicated variables for blanking fields")
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Jocelyn Falempe <jfalempe at redhat.com>
> Cc: Dave Airlie <airlied at redhat.com>
> Cc: dri-devel at lists.freedesktop.org
> Cc: <stable at vger.kernel.org> # v6.12+
> ---
>  drivers/gpu/drm/mgag200/mgag200_mode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
> index fb71658c3117..6067d08aeee3 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
> @@ -223,7 +223,7 @@ void mgag200_set_mode_regs(struct mga_device *mdev, const struct drm_display_mod
>  	vsyncstr = mode->crtc_vsync_start - 1;
>  	vsyncend = mode->crtc_vsync_end - 1;
>  	vtotal = mode->crtc_vtotal - 2;
> -	vblkstr = mode->crtc_vblank_start;
> +	vblkstr = mode->crtc_vblank_start - 1;
>  	vblkend = vtotal + 1;
>  
>  	linecomp = vdispend;
> -- 
> 2.49.0
> 
-- 
 Microsoft has beaten Volkswagen's world record.  Volkswagen only created 22
 million bugs.