On Sun, Oct 16, 2022 at 07:36:25PM +0800, Chun-Chao Yen wrote: > Problem Description: > The current way of handling the boundary case in tx, i.e. adding one-byte > padding when the size of an outbound packet is a multiple of the maximum > frame size used for USB bulk transfer, does not work with the hardware. > This can be shown by running a loading test via iperf with this hardware as > the sender; one can then tune the iperf parameters on the sender side (e.g. > "-M 510" in my testing environment) so that sent packets frequently hit the > boundary condition, and observe a significant drop in the transmission > rate. In the worst case (often after a long run), the hardware can stop > functioning (can not send or receive packets anymore, albeit the > corresponding network interface is still reported present by ifconfig). > > It is also believed that this problem is highly relevant to this bug [1]. > > Solution: > Enable FLAG_MULTI_PACKET and modify both ax88179_rx_fixup() and > ax88179_tx_fixup() accordingly. > > Rationale: > When FLAG_MULTI_PACKET is enabled (and FLAG_SEND_ZLP is off, which is the > case for this driver), usbnet will skip padding, and trust that each > sk_buff returned from the mini-driver's tx_fixup function has been taken > care of to cater for the requirement of its target hardware. That > mechanism allows this mini-driver to send, even when the boundary condition > is detected, "untampered" packets (no padding, no extra flags, as if in the > normal case) that the hardware accepts, and therefore resolves this > problem. > > Note that rather than being viewed as a workaround, enabling > FLAG_MULTI_PACKET is intended to better match the overall behaviour of the > hardware, as it also echos well the rx procedure conducting multiple-packet > extraction from a single sk_buff in ax88179_rx_fixup(). > > Verification: > Only tested with this device: > 0b95:1790 ASIX Electronics Corp. AX88179 Gigabit Ethernet > > References: > [1] https://bugzilla.kernel.org/show_bug.cgi?id=212731 > > Signed-off-by: Chun-Chao Yen <nothingstopsme@xxxxxxxxxxx> > --- > drivers/net/usb/ax88179_178a.c | 62 ++++++++++++++-------------------- > 1 file changed, 26 insertions(+), 36 deletions(-) Why is this a RESEND? Always put below the --- what is happening, what is different from the first version you sent? And why is this not threaded with the 2/3 and 3/3 patches? thanks, greg k-h
