Thanks, Marc and Kurt. >> Can you give me a pointer to this driver? Are you talking about the >> mainline linux-3.1? I sit corrected on this one. Further investigation indicates that this driver (authored by TI for AM335x) was never submitted to mainline Linux 3.1. Here is the link to the driver: https://github.com/calixtosystems/linux-am335x/tree/master/linux-am33x/drivers/net/can/d_can. >> 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. > I'm facing overflows, and have good results with the patchset I sent > last week. As Marc says, reading the mailboxes in NAPI softirq may cause > regular overflows. Ok. I see the newer changes to the c_can driver and will be trying those. --elenita On Thu, Oct 17, 2019 at 2:47 AM Kurt Van Dijck <dev.kurt@xxxxxxxxxxxxxxxxxxxxxx> wrote: > > On wo, 16 okt 2019 23:01:41 +0200, Marc Kleine-Budde wrote: > > 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. > > I'm facing overflows, and have good results with the patchset I sent > last week. As Marc says, reading the mailboxes in NAPI softirq may cause > regular overflows. > > Kurt
