linux-kernel - Re: [PATCH 2/3] fbcon: Add an option to disable fbcon in panic.

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Message-ID: <ZpfdcC2Es9rweHW_@phenom.ffwll.local>
Date: Wed, 17 Jul 2024 17:04:16 +0200
From: Daniel Vetter <daniel.vetter@...ll.ch>
To: Jocelyn Falempe <jfalempe@...hat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Helge Deller <deller@....de>,
	"Jiri Slaby (SUSE)" <jirislaby@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Javier Martinez Canillas <javierm@...hat.com>,
	Samuel Thibault <samuel.thibault@...-lyon.org>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-fbdev@...r.kernel.org
Subject: Re: [PATCH 2/3] fbcon: Add an option to disable fbcon in panic.

On Wed, Jul 17, 2024 at 10:48:40AM +0200, Jocelyn Falempe wrote:
> This is required to avoid conflict between DRM_PANIC, and fbcon. If
> a drm device already handle panic with drm_panic, it should set
> the skip_panic field in fb_info, so that fbcon will stay quiet, and
> not overwrite the panic_screen.
> 
> Signed-off-by: Jocelyn Falempe <jfalempe@...hat.com>
> ---
>  drivers/gpu/drm/drm_fb_helper.c  | 2 ++
>  drivers/video/fbdev/core/fbcon.c | 7 ++++++-
>  include/linux/fb.h               | 1 +
>  3 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index e2e19f49342e..3662d664d8f9 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -40,6 +40,7 @@
>  #include <drm/drm_fourcc.h>
>  #include <drm/drm_framebuffer.h>
>  #include <drm/drm_modeset_helper_vtables.h>
> +#include <drm/drm_panic.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_vblank.h>
>  
> @@ -524,6 +525,7 @@ struct fb_info *drm_fb_helper_alloc_info(struct drm_fb_helper *fb_helper)
>  	fb_helper->info = info;
>  	info->skip_vt_switch = true;
>  
> +	info->skip_panic = drm_panic_is_enabled(fb_helper->dev);
>  	return info;
>  
>  err_release:

Bit a bikeshed, but I'd split this patch out since it's for drm's fbdev
emulation, not the fbcon core code. With that:

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 3f7333dca508..498d9c07df80 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -270,12 +270,17 @@ static int fbcon_get_rotate(struct fb_info *info)
>  	return (ops) ? ops->rotate : 0;
>  }
>  
> +static bool fbcon_skip_panic(struct fb_info *info)
> +{
> +	return (info->skip_panic && unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID));
> +}
> +
>  static inline int fbcon_is_inactive(struct vc_data *vc, struct fb_info *info)
>  {
>  	struct fbcon_ops *ops = info->fbcon_par;
>  
>  	return (info->state != FBINFO_STATE_RUNNING ||
> -		vc->vc_mode != KD_TEXT || ops->graphics);
> +		vc->vc_mode != KD_TEXT || ops->graphics || fbcon_skip_panic(info));
>  }
>  
>  static int get_color(struct vc_data *vc, struct fb_info *info,
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index db7d97b10964..865dad03e73e 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -510,6 +510,7 @@ struct fb_info {
>  	void *par;
>  
>  	bool skip_vt_switch; /* no VT switch on suspend/resume required */
> +	bool skip_panic; /* Do not write to the fb after a panic */
>  };
>  
>  /* This will go away
> -- 
> 2.45.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch