drm/nouveau/kms/nve4-nv108: Limit cursors to 128x128

While Kepler does technically support 256x256 cursors, it turns out that
Kepler actually has some additional requirements for scanout surfaces that
we're not enforcing correctly, which aren't present on Maxwell and later.
Cursor surfaces must always use small pages (4K), and overlay surfaces must
always use large pages (128K).

Fixing this correctly though will take a bit more work: as we'll need to
add some code in prepare_fb() to move cursor FBs in large pages to small
pages, and vice-versa for overlay FBs. So until we have the time to do
that, just limit cursor surfaces to 128x128 - a size small enough to always
default to small pages.

This means small ovlys are still broken on Kepler, but it is extremely
unlikely anyone cares about those anyway :).

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: d3b2f0f7921c ("drm/nouveau/kms/nv50-: Report max cursor size to userspace")
Cc: <stable@vger.kernel.org> # v5.11+
---
 drivers/gpu/drm/nouveau/dispnv50/disp.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

On Thu, Mar 04, 2021 at 08:52:41PM -0500, Lyude Paul wrote:
> While Kepler does technically support 256x256 cursors, it turns out that
> Kepler actually has some additional requirements for scanout surfaces that
> we're not enforcing correctly, which aren't present on Maxwell and later.
> Cursor surfaces must always use small pages (4K), and overlay surfaces must
> always use large pages (128K).
> 
> Fixing this correctly though will take a bit more work: as we'll need to
> add some code in prepare_fb() to move cursor FBs in large pages to small
> pages, and vice-versa for overlay FBs. So until we have the time to do
> that, just limit cursor surfaces to 128x128 - a size small enough to always
> default to small pages.
> 
> This means small ovlys are still broken on Kepler, but it is extremely
> unlikely anyone cares about those anyway :).
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: d3b2f0f7921c ("drm/nouveau/kms/nv50-: Report max cursor size to userspace")
> Cc: <stable@vger.kernel.org> # v5.11+

I was experiencing problems with the mouse cursor on my system in v5.11
and after a bisect to help me search the web I found my way to this
patch, which fixed the problem for me.

Mine is an Armv8 system but there is nothing particularly exotic from a
graphics card or software point of view: Debian bullseye/wayland
(gnome-shell 3.38.3, mesa-20.3.4) running on a GT-710.

However FWIW:
Tested-by: Daniel Thompson <daniel.thompson@linaro.org>


Daniel.


> ---
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index 196612addfd6..1c9c0cdf85db 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -2693,9 +2693,20 @@ nv50_display_create(struct drm_device *dev)
>  	else
>  		nouveau_display(dev)->format_modifiers = disp50xx_modifiers;
>  
> -	if (disp->disp->object.oclass >= GK104_DISP) {
> +	/* FIXME: 256x256 cursors are supported on Kepler, however unlike Maxwell and later
> +	 * generations Kepler requires that we use small pages (4K) for cursor scanout surfaces. The
> +	 * proper fix for this is to teach nouveau to migrate fbs being used for the cursor plane to
> +	 * small page allocations in prepare_fb(). When this is implemented, we should also force
> +	 * large pages (128K) for ovly fbs in order to fix Kepler ovlys.
> +	 * But until then, just limit cursors to 128x128 - which is small enough to avoid ever using
> +	 * large pages.
> +	 */
> +	if (disp->disp->object.oclass >= GM107_DISP) {
>  		dev->mode_config.cursor_width = 256;
>  		dev->mode_config.cursor_height = 256;
> +	} else if (disp->disp->object.oclass >= GK104_DISP) {
> +		dev->mode_config.cursor_width = 128;
> +		dev->mode_config.cursor_height = 128;
>  	} else {
>  		dev->mode_config.cursor_width = 64;
>  		dev->mode_config.cursor_height = 64;
> -- 
> 2.29.2
> 
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