[PATCH 1/2] drm: mcde: Fix display initialization problem

[Sam Ravnborg]

Hi Linus.

On Sun, Jun 14, 2020 at 12:30:26AM +0200, Linus Walleij wrote:
> The following bug appeared in the MCDE driver/display
> initialization during the recent merge window.
> 
> First the place we call drm_fbdev_generic_setup() in the
> wrong place: this needs to be called AFTER calling
> drm_dev_register() else we get this splat:
> 
>  ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1 at ../drivers/gpu/drm/drm_fb_helper.c:2198 drm_fbdev_generic_setup+0x164/0x1a8
> mcde a0350000.mcde: Device has not been registered.
> Modules linked in:
> Hardware name: ST-Ericsson Ux5x0 platform (Device Tree Support)
> [<c010e704>] (unwind_backtrace) from [<c010a86c>] (show_stack+0x10/0x14)
> [<c010a86c>] (show_stack) from [<c0414f38>] (dump_stack+0x9c/0xb0)
> [<c0414f38>] (dump_stack) from [<c0121c8c>] (__warn+0xb8/0xd0)
> [<c0121c8c>] (__warn) from [<c0121d18>] (warn_slowpath_fmt+0x74/0xb8)
> [<c0121d18>] (warn_slowpath_fmt) from [<c04b154c>] (drm_fbdev_generic_setup+0x164/0x1a8)
> [<c04b154c>] (drm_fbdev_generic_setup) from [<c04ed278>] (mcde_drm_bind+0xc4/0x160)
> [<c04ed278>] (mcde_drm_bind) from [<c04f06b8>] (try_to_bring_up_master+0x15c/0x1a4)
> (...)
> 
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>

Yup, this is the right way to do it.

Reviewed-by: Sam Ravnborg <sam at ravnborg.org>

One small thing to consider, see below. But for another patch.

> ---
>  drivers/gpu/drm/mcde/mcde_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mcde/mcde_drv.c b/drivers/gpu/drm/mcde/mcde_drv.c
> index 84f3e2dbd77b..80082d6dce3a 100644
> --- a/drivers/gpu/drm/mcde/mcde_drv.c
> +++ b/drivers/gpu/drm/mcde/mcde_drv.c
> @@ -209,7 +209,6 @@ static int mcde_modeset_init(struct drm_device *drm)
>  
>  	drm_mode_config_reset(drm);
>  	drm_kms_helper_poll_init(drm);
> -	drm_fbdev_generic_setup(drm, 32);
>  
>  	return 0;
>  }
> @@ -264,6 +263,8 @@ static int mcde_drm_bind(struct device *dev)
>  	if (ret < 0)
>  		goto unbind;
>  
> +	drm_fbdev_generic_setup(drm, 32);
Consider using mode_config.preferred_depth, then you can pass 0 here.


> +
>  	return 0;
>  
>  unbind:
> -- 
> 2.26.2
> 
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