[PATCH] usb: Add delay for control messages to reach usb stick

[Janne Grunau]

Hej,

On 2022-08-25 23:35:33 -0600, Ashok Reddy Soma wrote:
> We are seeing timing issues with transcend usb sticks. These devices
> seems to require more time than regular devices for the control messages
> to reach device. Add 1ms delay before sending control message to fix
> trancend device detection issue.

I suspect I see something similar with the DWC3 controller on Apple 
M1/M2 devices. It seems to be related to USB full speed devices with 
bMaxPacketSize0 of 8. Failing devices are so only keyboards since that 
is a device everyone will connect when using a Mac Mini as desktop.
I can reproduce the issue with older Logitech Unifying Receiver wireless 
keyboard/mouse dongles (bcdDevice 12.03 or 12.10). I could also resolve 
the issue with random 'mdelay(1);'. I chased the cause of the issue down 
to the initial USB descriptor read to parse 'bMaxPacketSize0' in 
usb_setup_descriptor(). Please test if adding the delay after the 
get_descriptor_len() call in usb_setup_descriptor() is enough.
On the Apple silicon devices reducing the read size from 64 byte to 8 
resolves the issue as well. Please try attached work-in-progress patch 
(comment and commit message are not finalized).

HTH Janne
 
> Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma at amd.com>
> ---
> 
>  common/usb.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/common/usb.c b/common/usb.c
> index 6fcf1e8428..3fae32b048 100644
> --- a/common/usb.c
> +++ b/common/usb.c
> @@ -241,6 +241,12 @@ int usb_control_msg(struct usb_device *dev, unsigned int pipe,
>  	      request, requesttype, value, index, size);
>  	dev->status = USB_ST_NOT_PROC; /*not yet processed */
>  
> +	/* Timing issues are observed with transcend usb sticks such as
> +	 * “Transcend Jetflash 350 USB2.0". Add 1ms delay for the usb
> +	 * device to get detected.
> +	 */
> +	mdelay(1);

Please let's try to avoid this. I noticed a slowdown of USB probing with 
an hub with 4 devices connected. Since Apple silicon devices are desktop 
style machines I expect it's not uncommon to see systems with many USB 
devices.

> +
>  	err = submit_control_msg(dev, pipe, data, size, setup_packet);
>  	if (err < 0)
>  		return err;
> -- 
> 2.17.1
> 
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