On 07.07.2023 15:47:12, Judith Mendez wrote: > On AM62x there are two MCANs 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 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. > 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. Latency > 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 However > 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. > > v9: > Link: https://lore.kernel.org/linux-can/20230419223323.20384-1-jm@xxxxxx/T/#t > > v8: > Link: https://lore.kernel.org/linux-can/20230530224820.303619-1-jm@xxxxxx/T/#t > > v7: > Link: https://lore.kernel.org/linux-can/20230523023749.4526-1-jm@xxxxxx/T/#t > > v6: > Link: https://lore.kernel.org/linux-can/20230518193613.15185-1-jm@xxxxxx/T/#t > > v5: > Link: https://lore.kernel.org/linux-can/20230510202952.27111-1-jm@xxxxxx/T/#t > > v4: > Link: https://lore.kernel.org/linux-can/c3395692-7dbf-19b2-bd3f-31ba86fa4ac9@xxxxxxxxxx/T/#t The link doesn't point to v4, fixed. > 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 Was there a v1? That link doesn't point to it, removed. > > RFC: > Link: https://lore.kernel.org/linux-can/52a37e51-4143-9017-42ee-8d17c67028e3@xxxxxx/T/#t Doesn't point to RFC, fixed. Applied to linux-can-next/testing. Thanks, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung Nürnberg | Phone: +49-5121-206917-129 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |
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