Re: [PATCH v2] drm/udl: Ensure channel is selected before using the device.

[poma <pomidorabelisima@gmail.com>]

On 23.08.2016 07:57, Daniel Vetter wrote:
> On Mon, Aug 22, 2016 at 11:17:34PM +0100, Jamie Lentin wrote:
>> Lift configuration command from udlfb. This appears to be essential for
>> at least a Rextron VCUD-60, without which no URB communication occurs.
>>
>> Signed-off-by: Jamie Lentin <jm@lentin.co.uk>
>> ---
>> udl_encoder_commit() is too late to do this set up in it seems. This
>> setup doesn't need to be performed again after a suspend, although this
>> is somewhat academic until I send the patch adding suspend and resume
>> functions.
>>
>> Tested with a Rextron VCUD-60 attached to a Thinkpad X201s on Linux 4.7.0
> 
> Applied to drm-misc, thanks.
> -Daniel
> 
>>
>> Cheers,
>> ---
>>  drivers/gpu/drm/udl/udl_main.c | 25 +++++++++++++++++++++++++
>>  1 file changed, 25 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
>> index 33dbfb2..29f0207 100644
>> --- a/drivers/gpu/drm/udl/udl_main.c
>> +++ b/drivers/gpu/drm/udl/udl_main.c
>> @@ -16,6 +16,8 @@
>>  /* -BULK_SIZE as per usb-skeleton. Can we get full page and avoid overhead? */
>>  #define BULK_SIZE 512
>>  
>> +#define NR_USB_REQUEST_CHANNEL 0x12
>> +
>>  #define MAX_TRANSFER (PAGE_SIZE*16 - BULK_SIZE)
>>  #define WRITES_IN_FLIGHT (4)
>>  #define MAX_VENDOR_DESCRIPTOR_SIZE 256
>> @@ -90,6 +92,26 @@ success:
>>  	return true;
>>  }
>>  
>> +/*
>> + * Need to ensure a channel is selected before submitting URBs
>> + */
>> +static int udl_select_std_channel(struct udl_device *udl)
>> +{
>> +	int ret;
>> +	u8 set_def_chn[] = {0x57, 0xCD, 0xDC, 0xA7,
>> +			    0x1C, 0x88, 0x5E, 0x15,
>> +			    0x60, 0xFE, 0xC6, 0x97,
>> +			    0x16, 0x3D, 0x47, 0xF2};
>> +
>> +	ret = usb_control_msg(udl->udev,
>> +			      usb_sndctrlpipe(udl->udev, 0),
>> +			      NR_USB_REQUEST_CHANNEL,
>> +			      (USB_DIR_OUT | USB_TYPE_VENDOR), 0, 0,
>> +			      set_def_chn, sizeof(set_def_chn),
>> +			      USB_CTRL_SET_TIMEOUT);
>> +	return ret < 0 ? ret : 0;
>> +}
>> +
>>  static void udl_release_urb_work(struct work_struct *work)
>>  {
>>  	struct urb_node *unode = container_of(work, struct urb_node,
>> @@ -301,6 +323,9 @@ int udl_driver_load(struct drm_device *dev, unsigned long flags)
>>  		goto err;
>>  	}
>>  
>> +	if (udl_select_std_channel(udl))
>> +		DRM_ERROR("Selecting channel failed\n");
>> +
>>  	if (!udl_alloc_urb_list(dev, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
>>  		DRM_ERROR("udl_alloc_urb_list failed\n");
>>  		goto err;
>> -- 
>> 2.8.1
>>
> 

It doesn't breaks the device, however under the hood it is boiling,

------------[ cut here ]------------
WARNING: CPU: 0 PID: 381 at drivers/usb/core/hcd.c:1584 usb_hcd_map_urb_for_dma+0x49f/0x770
transfer buffer not dma capable
Modules linked in: ... udl(+) ... drm_kms_helper ... drm ...
CPU: 0 PID: 381 Comm: systemd-udevd Not tainted 4.9.0-0.rc4.git0.1.fc26.x86_64+debug #1
...
Call Trace:
 [<ffffffffb646b1b3>] dump_stack+0x86/0xc3
 [<ffffffffb60af55b>] __warn+0xcb/0xf0
 [<ffffffffb60af5df>] warn_slowpath_fmt+0x5f/0x80
 [<ffffffffb649e86b>] ? debug_dma_mapping_error+0x7b/0x90
 [<ffffffffb6694a8f>] usb_hcd_map_urb_for_dma+0x49f/0x770
 [<ffffffffb6110e25>] ? trace_hardirqs_on_caller+0xf5/0x1b0
 [<ffffffffb669539d>] usb_hcd_submit_urb+0x34d/0xb50
 [<ffffffffb6110d06>] ? mark_held_locks+0x76/0xa0
 [<ffffffffb6116601>] ? __raw_spin_lock_init+0x21/0x60
 [<ffffffffb6110e25>] ? trace_hardirqs_on_caller+0xf5/0x1b0
 [<ffffffffb6696d74>] usb_submit_urb+0x2f4/0x560
 [<ffffffffb610e171>] ? lockdep_init_map+0x61/0x210
 [<ffffffffb66976f4>] usb_start_wait_urb+0x74/0x180
 [<ffffffffb66978dc>] usb_control_msg+0xdc/0x120
 [<ffffffffc08923e1>] udl_driver_load+0x141/0x590 [udl]
 [<ffffffffb6110e01>] ? trace_hardirqs_on_caller+0xd1/0x1b0
 [<ffffffffc059fbe9>] drm_dev_register+0xa9/0xd0 [drm]
 [<ffffffffc08910c2>] udl_usb_probe+0x42/0x90 [udl]
 [<ffffffffb669c18f>] usb_probe_interface+0x15f/0x2d0
 [<ffffffffb65eb2f3>] driver_probe_device+0x223/0x430
 [<ffffffffb65eb5e3>] __driver_attach+0xe3/0xf0
 [<ffffffffb65eb500>] ? driver_probe_device+0x430/0x430
 [<ffffffffb65e8bf3>] bus_for_each_dev+0x73/0xc0
 [<ffffffffb65eaa1e>] driver_attach+0x1e/0x20
 [<ffffffffb65ea443>] bus_add_driver+0x173/0x270
 [<ffffffffb65ec240>] driver_register+0x60/0xe0
 [<ffffffffb669a9fa>] usb_register_driver+0xaa/0x160
 [<ffffffffc089a000>] ? 0xffffffffc089a000
 [<ffffffffc089a01e>] udl_driver_init+0x1e/0x1000 [udl]
 [<ffffffffb6002190>] do_one_initcall+0x50/0x180
 [<ffffffffb6131045>] ? rcu_read_lock_sched_held+0x45/0x80
 [<ffffffffb6275787>] ? kmem_cache_alloc_trace+0x277/0x2d0
 [<ffffffffb61fb2ce>] ? do_init_module+0x27/0x1f1
 [<ffffffffb61fb306>] do_init_module+0x5f/0x1f1
 [<ffffffffb615e3d1>] load_module+0x2401/0x2b40
 [<ffffffffb615ac00>] ? __symbol_put+0x70/0x70
 [<ffffffffb60ecd10>] ? sched_clock_cpu+0x90/0xc0
 [<ffffffffb615ecab>] SYSC_init_module+0x19b/0x1c0
 [<ffffffffb615edee>] SyS_init_module+0xe/0x10
 [<ffffffffb6003eec>] do_syscall_64+0x6c/0x1f0
 [<ffffffffb690bd49>] entry_SYSCALL64_slow_path+0x25/0x25
---[ end trace 1fa5e22a0dcf62da ]---
[drm:udl_driver_load [udl]] *ERROR* Selecting channel failed
udl 1-2:1.0: fb1: udldrmfb frame buffer device
[drm] Initialized udl on minor 1
usbcore: registered new interface driver udl


Is this expected WARN?


Ref.
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/udl?id=d1c151dc
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/core/hcd.c?id=refs/tags/v4.9-rc4#n1584