linux-kernel - Re: [PATCH] drm/udl: Increase GET_URB

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Message-ID: <561e6365-f75c-44cf-8f7d-9f84ee459dac@suse.de>
Date: Wed, 5 Nov 2025 11:13:53 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: oushixiong1025@....com, Dave Airlie <airlied@...hat.com>
Cc: Sean Paul <sean@...rly.run>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, Shixiong Ou <oushixiong@...inos.cn>
Subject: Re: [PATCH] drm/udl: Increase GET_URB_TIMEOUT

Hi

Am 05.11.25 um 10:59 schrieb oushixiong1025@....com:
> From: Shixiong Ou <oushixiong@...inos.cn>
>
> [WHY]
> A situation has occurred where udl_handle_damage() executed successfully
> and the kernel log appears normal, but the display fails to show any output.
> This is because the call to udl_get_urb() in udl_crtc_helper_atomic_enable()
> failed without generating any error message.
>
> [HOW]
> 1. Increase GET_URB_TIMEOUT.
> 2. Add error messages when calling udl_get_urb() failed in
> udl_crtc_helper_atomic_enable().
>
> Signed-off-by: Shixiong Ou <oushixiong@...inos.cn>
> ---
>   drivers/gpu/drm/udl/udl_main.c    | 2 +-
>   drivers/gpu/drm/udl/udl_modeset.c | 5 ++++-
>   2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
> index bc58991a6f14..dd9576fd4ff0 100644
> --- a/drivers/gpu/drm/udl/udl_main.c
> +++ b/drivers/gpu/drm/udl/udl_main.c
> @@ -285,7 +285,7 @@ static struct urb *udl_get_urb_locked(struct udl_device *udl, long timeout)
>   	return unode->urb;
>   }
>   
> -#define GET_URB_TIMEOUT	HZ
> +#define GET_URB_TIMEOUT	(HZ * 2)
>   struct urb *udl_get_urb(struct udl_device *udl)
>   {
>   	struct urb *urb;
> diff --git a/drivers/gpu/drm/udl/udl_modeset.c b/drivers/gpu/drm/udl/udl_modeset.c
> index 231e829bd709..647af04f194e 100644
> --- a/drivers/gpu/drm/udl/udl_modeset.c
> +++ b/drivers/gpu/drm/udl/udl_modeset.c
> @@ -21,6 +21,7 @@
>   #include <drm/drm_gem_framebuffer_helper.h>
>   #include <drm/drm_gem_shmem_helper.h>
>   #include <drm/drm_modeset_helper_vtables.h>
> +#include <drm/drm_print.h>
>   #include <drm/drm_probe_helper.h>
>   #include <drm/drm_vblank.h>
>   
> @@ -342,8 +343,10 @@ static void udl_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atom
>   		return;
>   
>   	urb = udl_get_urb(udl);
> -	if (!urb)
> +	if (!urb) {
> +		DRM_ERROR("Udl get urb failed when enabling crtc");

This line can possibly fill your kernel logs quickly. Use drm_dbg() or 
drm_err_ratelimited() here. And there's no need to explicitly mention 
'Udl' with them.

Best regards
Thomas

>   		goto out;
> +	}
>   
>   	buf = (char *)urb->transfer_buffer;
>   	buf = udl_vidreg_lock(buf);

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)