Hello all, On 5/1/23 17:31, Judith Mendez wrote: > On AM62x there is one MCAN in MAIN domain and two in MCU domain. > The MCANs in MCU domain were not enabled since there is no > hardware interrupt routed to A53 GIC interrupt controller. > Therefore A53 Linux cannot be interrupted by MCU MCANs. > > This solution instantiates a hrtimer with 1 ms polling interval > for MCAN device when there is no hardware interrupt and there is > poll-interval property in DTB MCAN node. The hrtimer generates a > recurring software interrupt which allows to call the isr. The isr > will check if there is pending transaction by reading a register > and proceed normally if there is. > > On AM62x, this series enables two MCU MCAN which will use the hrtimer > implementation. MCANs with hardware interrupt routed to A53 Linux > will continue to use the hardware interrupt as expected. > > Timer polling method was tested on both classic CAN and CAN-FD > at 125 KBPS, 250 KBPS, 1 MBPS and 2.5 MBPS with 4 MBPS bitrate > switching. > > Letency and CPU load benchmarks were tested on 3x MCAN on AM62x. > 1 MBPS timer polling interval is the better timer polling interval > since it has comparable latency to hardware interrupt with the worse > case being 1ms + CAN frame propagation time and CPU load is not > substantial. Latency can be improved further with less than 1 ms > polling intervals, howerver it is at the cost of CPU usage since CPU > load increases at 0.5 ms. > > Note that in terms of power, enabling MCU MCANs with timer-polling > implementation might have negative impact since we will have to wake > up every 1 ms whether there are CAN packets pending in the RX FIFO or > not. This might prevent the CPU from entering into deeper idle states > for extended periods of time. > > This patch series depends on 'Enable CAN PHY transceiver driver': > Link: https://lore.kernel.org/lkml/775ec9ce-7668-429c-a977-6c8995968d6e@xxxxxxxxxxxxxxxx/T/ > > v2: > Link: https://lore.kernel.org/linux-can/20230424195402.516-1-jm@xxxxxx/T/#t > > V1: > Link: https://lore.kernel.org/linux-can/19d8ae7f-7b74-a869-a818-93b74d106709@xxxxxx/T/#t > > RFC: > Link: https://lore.kernel.org/linux-can/52a37e51-4143-9017-42ee-8d17c67028e3@xxxxxx/T/#t > > Changes since v2: > - Change binding patch first > - Update binding poll-interval description > - Add oneOf to select either interrupts/interrupt-names or poll-interval > - Sort list of includes > - Create a define for 1 ms polling interval > - Change plarform_get_irq to optional to not print error msg > - Fix indentations, lengths of code lines, and added other style changes > > Changes since v1: > - Add poll-interval property to bindings and MCAN DTB node > - Add functionality to check for 'poll-interval' property in MCAN node > - Bindings: add an example using poll-interval > - Add 'polling' flag in driver to check if device is using polling method > - Check for both timer polling and hardware interrupt case, default to > hardware interrupt method > - Change ns_to_ktime() to ms_to_ktime() Please ignore this version v3, apologies for sending the wrong patches. regards, Judith
