On 10/16/19 9:06 PM, Elenita Hinds wrote: > I'm hoping someone can help me with this ... > > The DCAN module I'm testing with supports 64 CAN messages and DMA. The > combined c_can/d_can driver seem to only support 16 RX message objects > and no DMA (as far as I can tell). ACK > I noticed that older Linux version > (3.1) implemented a separate d_can driver that supports both. I'm > wondering why these were removed from the latest c_can/d_can files. Can you give me a pointer to this driver? Are you talking about the mainline linux-3.1? > The reason for this question is I'm seeing frame losses and I think it > is due to the driver. Increasing the socket buffer sizes did not have > any effect; the number is overruns was still pretty large. > > Any feedback would be appreciated. The problem with the c_can and d_can is, that it doesn't have a proper FIFO but only mailboxes. And these mailboxes don't implement a timestamp, so that it's not that easy to read messages in the correct order. Does the device support bus master DMA? As CAN messages are quite small, the overhead of setting up DMA might be too high. The algorithm that tries to read the CAN frames in the correct order was added in v3.15. That algorithm should be ported to the rx-offload helper. This way the mailboxes can be read in interrupt context and not from NAPI (which runs in softirq context only). If this basically works, it can be extended to support 64 mailboxes. Marc -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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