Re: [PATCH] drm/meson: fix max mode_config height/width

[Daniel Vetter]

On Thu, Oct 04, 2018 at 10:42:43AM +0200, Neil Armstrong wrote:
> The mode_config max_width/max_height determines the maximum framebuffer
> size the pixel reader can handle. But the values were set thinking they
> were determining the maximum screen dimensions.
> 
> This patch changes the values to the maximum height/width the CANVAS block
> can handle rounded to some coherent values.
> 
> Fixes: a41e82e6c457 ("drm/meson: Add support for components")
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>

It's both. Grep for all the callers of ->fill_modes and you'll see that
this limit is also used to filter max screen sizes.

If you want to change this, then I think we need a new
mode_config.fb_max_width/height, which if non-zero, would extend the limit
for fbs.

There's also the problem that if you extend this for fbs, then there's no
check anymore in the atomic_commit paths (or legacy modeset), so that
needs to be addressed somehow too.

Bunch of igt to make sure we're not missing anything would be sweet on
top, e.g. e.g. trying to set a mode over the limit and making sure it
fails.

Cheers, Daniel

> ---
>  drivers/gpu/drm/meson/meson_drv.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_drv.c b/drivers/gpu/drm/meson/meson_drv.c
> index d344312..2e29968 100644
> --- a/drivers/gpu/drm/meson/meson_drv.c
> +++ b/drivers/gpu/drm/meson/meson_drv.c
> @@ -243,8 +243,8 @@ static int meson_drv_bind_master(struct device *dev, bool has_components)
>  		goto free_drm;
>  
>  	drm_mode_config_init(drm);
> -	drm->mode_config.max_width = 3840;
> -	drm->mode_config.max_height = 2160;
> +	drm->mode_config.max_width = 16384;
> +	drm->mode_config.max_height = 8192;
>  	drm->mode_config.funcs = &meson_mode_config_funcs;
>  
>  	/* Hardware Initialization */
> -- 
> 2.7.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch