Re: [PATCH] drm/udl: Increase get urb timeout for modeset

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 05.11.25 um 10:07 schrieb oushixiong:
> If the wait times for all operations increase, it would likely cause 
> significant blocking in the display process.

But we're usually not waiting until timeout, but only until the next urb 
becomes available again. And we have several in the queue pre-allocated. 
Increasing the timeout should therefore not be a problem.  The current 
drawing timeout of 1 second (== HZ) would already be a major issue 
otherwise.

> Should we make a distinction between the two, or base it on what you 
> said about increasing  the regular GET_URB_TIMEOUT for all operations ?

Please try to double the timeout.

(If this really doesn't work, we should try to drop the urb caching 
entirely and allocate urbs as we need them.)

Best regards
Thomas

>
> Best regards
> Shixiong
>
> 在 2025/11/5 16:57, Thomas Zimmermann 写道:
>> Hi
>>
>> Am 05.11.25 um 09:30 schrieb oushixiong1025@163.com:
>>> From: Shixiong Ou <oushixiong@kylinos.cn>
>>>
>>> [WHY]
>>> There is a situation where udl_handle_damage() was running successfully
>>> but the screen was black. it was because 
>>> udl_crtc_helper_atomic_enable() failed,
>>> and there were no error messages.
>>>
>>> [HOW]
>>> The priority for mode settings needs to be higher than damage 
>>> handle, requiring
>>> a higher success rate than ordinary operations.
>>> Increase get urb timeout for modeset.
>>>
>>> Signed-off-by: Shixiong Ou <oushixiong@kylinos.cn>
>>> ---
>>>   drivers/gpu/drm/udl/udl_drv.h      |  5 ++++-
>>>   drivers/gpu/drm/udl/udl_main.c     |  5 ++---
>>>   drivers/gpu/drm/udl/udl_modeset.c  | 11 +++++++----
>>>   drivers/gpu/drm/udl/udl_transfer.c |  2 +-
>>>   4 files changed, 14 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/udl/udl_drv.h 
>>> b/drivers/gpu/drm/udl/udl_drv.h
>>> index 145bb95ccc48..38b3bdf1ae4a 100644
>>> --- a/drivers/gpu/drm/udl/udl_drv.h
>>> +++ b/drivers/gpu/drm/udl/udl_drv.h
>>> @@ -31,6 +31,9 @@ struct drm_mode_create_dumb;
>>>   #define DRIVER_MINOR        0
>>>   #define DRIVER_PATCHLEVEL    1
>>>   +#define GET_URB_TIMEOUT    HZ
>>> +#define MODESET_GET_URB_TIMEOUT    (HZ*2)
>>> +
>>
>> Just increase the regular GET_URB_TIMEOUT for all operations.
>>
>> Best regards
>> Thomas
>>
>>>   struct udl_device;
>>>     struct urb_node {
>>> @@ -72,7 +75,7 @@ static inline struct usb_device 
>>> *udl_to_usb_device(struct udl_device *udl)
>>>   int udl_modeset_init(struct udl_device *udl);
>>>   struct drm_connector *udl_connector_init(struct drm_device *dev);
>>>   -struct urb *udl_get_urb(struct udl_device *udl);
>>> +struct urb *udl_get_urb(struct udl_device *udl, long timeout);
>>>     int udl_submit_urb(struct udl_device *udl, struct urb *urb, 
>>> size_t len);
>>>   void udl_sync_pending_urbs(struct udl_device *udl);
>>> diff --git a/drivers/gpu/drm/udl/udl_main.c 
>>> b/drivers/gpu/drm/udl/udl_main.c
>>> index bc58991a6f14..891996f0f74b 100644
>>> --- a/drivers/gpu/drm/udl/udl_main.c
>>> +++ b/drivers/gpu/drm/udl/udl_main.c
>>> @@ -285,13 +285,12 @@ static struct urb *udl_get_urb_locked(struct 
>>> udl_device *udl, long timeout)
>>>       return unode->urb;
>>>   }
>>>   -#define GET_URB_TIMEOUT    HZ
>>> -struct urb *udl_get_urb(struct udl_device *udl)
>>> +struct urb *udl_get_urb(struct udl_device *udl, long timeout)
>>>   {
>>>       struct urb *urb;
>>>         spin_lock_irq(&udl->urbs.lock);
>>> -    urb = udl_get_urb_locked(udl, GET_URB_TIMEOUT);
>>> +    urb = udl_get_urb_locked(udl, timeout);
>>>       spin_unlock_irq(&udl->urbs.lock);
>>>       return urb;
>>>   }
>>> diff --git a/drivers/gpu/drm/udl/udl_modeset.c 
>>> b/drivers/gpu/drm/udl/udl_modeset.c
>>> index 231e829bd709..6adca5e3e471 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>
>>>   @@ -217,7 +218,7 @@ static int udl_handle_damage(struct 
>>> drm_framebuffer *fb,
>>>           return ret;
>>>       log_bpp = ret;
>>>   -    urb = udl_get_urb(udl);
>>> +    urb = udl_get_urb(udl, GET_URB_TIMEOUT);
>>>       if (!urb)
>>>           return -ENOMEM;
>>>       cmd = urb->transfer_buffer;
>>> @@ -341,9 +342,11 @@ static void 
>>> udl_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atom
>>>       if (!drm_dev_enter(dev, &idx))
>>>           return;
>>>   -    urb = udl_get_urb(udl);
>>> -    if (!urb)
>>> +    urb = udl_get_urb(udl, MODESET_GET_URB_TIMEOUT);
>>> +    if (!urb) {
>>> +        DRM_ERROR("Udl get urb failed when enabling crtc");
>>>           goto out;
>>> +    }
>>>         buf = (char *)urb->transfer_buffer;
>>>       buf = udl_vidreg_lock(buf);
>>> @@ -374,7 +377,7 @@ static void 
>>> udl_crtc_helper_atomic_disable(struct drm_crtc *crtc, struct drm_ato
>>>       if (!drm_dev_enter(dev, &idx))
>>>           return;
>>>   -    urb = udl_get_urb(udl);
>>> +    urb = udl_get_urb(udl, MODESET_GET_URB_TIMEOUT);
>>>       if (!urb)
>>>           goto out;
>>>   diff --git a/drivers/gpu/drm/udl/udl_transfer.c 
>>> b/drivers/gpu/drm/udl/udl_transfer.c
>>> index 7d670b3a5293..858b47522d78 100644
>>> --- a/drivers/gpu/drm/udl/udl_transfer.c
>>> +++ b/drivers/gpu/drm/udl/udl_transfer.c
>>> @@ -202,7 +202,7 @@ int udl_render_hline(struct udl_device *udl, int 
>>> log_bpp, struct urb **urb_ptr,
>>>               int ret = udl_submit_urb(udl, urb, len);
>>>               if (ret)
>>>                   return ret;
>>> -            urb = udl_get_urb(udl);
>>> +            urb = udl_get_urb(udl, GET_URB_TIMEOUT);
>>>               if (!urb)
>>>                   return -EAGAIN;
>>>               *urb_ptr = urb;
>>
>

-- 
--
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)