On 05.08.2021 22:19:00, Dario Binacchi wrote: > As reported by a comment in the c_can_start_xmit() this was not a FIFO. > C/D_CAN controller sends out the buffers prioritized so that the lowest > buffer number wins. > > What did c_can_start_xmit() do if head was less tail in the tx ring ? It > waited until all the frames queued in the FIFO was actually transmitted > by the controller before accepting a new CAN frame to transmit, even if > the FIFO was not full, to ensure that the messages were transmitted in > the order in which they were loaded. > > By storing the frames in the FIFO without requiring its transmission, we > will be able to use the full size of the FIFO even in cases such as the > one described above. The transmission interrupt will trigger their > transmission only when all the messages previously loaded but stored in > less priority positions of the buffers have been transmitted. > > Suggested-by: Gianluca Falavigna <gianluca.falavigna@xxxxxxxxx> > Signed-off-by: Dario Binacchi <dariobin@xxxxxxxxx> My review from https://lore.kernel.org/linux-can/20210806092523.hij5ejjq6wecbgfr@xxxxxxxxxxxxxx/ applies here, too. Please use IF_RX in c_can_do_tx(), remove the spin_lock and test. After applying your series, I'll send a patch that changes IF_RX into IF_NAPI to avoid any further confusion. regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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