On 11.08.2025 23:06:09, Stefan Mätje wrote:

The driver tried to keep as much CAN frames as possible submitted to the
USB device (ESD_USB_MAX_TX_URBS). This has led to occasional "No free
context" error messages in high load situations like with
"cangen -g 0 -p 10 canX".

This patch now calls netif_stop_queue() already if the number of active
jobs reaches ESD_USB_TX_URBS_HI_WM which is < ESD_USB_MAX_TX_URBS.
The netif_start_queue() is called in esd_usb_tx_done_msg() only if
the number of active jobs is <= ESD_USB_TX_URBS_LO_WM.

This change eliminates the occasional error messages and significantly
reduces the number of calls to netif_start_queue() and
netif_stop_queue().

The watermark limits have been chosen with the CAN-USB/Micro in mind to
not to compromise its TX throughput. This device is running on USB 1.1
only with its 1ms USB polling cycle where a ESD_USB_TX_URBS_LO_WM
value below 9 decreases the TX throughput.

Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>

Please add a Fixes tag.

Marc

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