Hello Philip, Gedare and others interested in RTEMS CAN/CAN FD API, On Tuesday 22 of August 2023 14:11:22 Philip Kirkpatrick wrote: > Thank you for your input on this. I'm still digesting LinCAN, but it looks > like a good way to go. On our end, we will likely have some resources to > throw at this in a few weeks.
LinCAN has been designed as full featured, vendor neutral character driver API based CAN stack for Linux and RTOS RT Linux kernel with ability to be accessed from Linux user-land and RT Linux modules in the second case. https://ortcan.sourceforge.net/lincan/ But SocketCAN is the choice for Linux kernel CAN support today. It has nicer API but has it problems on real-time side etc... Even from our experience with NuttX CAN drivers development I tend to stay with character driver API for RTEMS in the current iteration... Potability of LinCAN to RTEMS and even bare metal HW without scheduler has been taken in mind. There is a branch can-usb1 which used slightly modified SJA1000 LinCAN chip driver together with LinCAN infrastructure to provide low level API (only FIFOs, no POSIX read/write call) in system less mode to implement USB to CAN converter on old NXP LPC21xx and SJA1000 or newer LPC17xx targets https://sourceforge.net/p/ortcan/lincan/ci/can-usb1/tree/embedded/app/usbcan/ We have implemented the companion Linux kernel LinCAN and SocketCAN drivers which allowed to use even USB converter in addition to ISA and PCI bus connected CAN controllers... > On Thu, Aug 17, 2023 at 4:26 PM Gedare Bloom <ged...@rtems.org> wrote: > > Hi Phil, > > > > On Wed, Aug 9, 2023 at 6:38 AM Philip Kirkpatrick > > > > <p.kirkpatr...@reflexaerospace.com> wrote: > > > Hello, > > > > > > Some people on our team here at Reflex are preparing to implement some > > > > CAN drivers. Specifically for TMS570 and for ZynqMP-RPU (side note my > > latest patch for that on Jun 29th is still sitting there unreviewed). I > > was wondering what the current status of the CAN API is. > > Feel free to ping the patch. At the moment, this email based system is > > all we have, and sometimes patches may not get a lot of attention > > especially if no one "owns" it -- such as new BSPs. > > > > > I saw in August of last year and API was added and then last month was > > > > reverted with this patch: > > > https://lists.rtems.org/pipermail/devel/2023-July/076013.html > > > The comment on the patch says the API isn't mature enough for release. > > > > What deficiencies need to be resolved in the API, is this being actively > > worked on, and should we design against this API or is there a different > > API we should target? We plan keeping CAN/CAN FD structure (discussed and agreed upon with Oliver Hartkopp) and keep barely the same read/write code as is in already included CAN solution. I consider deep redesign of the rest as a must. > > The implementation of that API was deficient. It did not support > > multiple read/write transactions, it had a custom-built ring buffer > > that was not fully vetted, and some other problems related to > > threads+priorities. I expect to have some time to look at how to > > provide better CAN support inside of RTEMS. This has been an ongoing > > discussion I've been having with Pavel Pisa and others for many years > > now (a decade?). The direction that I will prefer to go is to port > > LinCAN > > https://cmp.felk.cvut.cz/~pisa/can/doc/lincandoc-0.3.5.pdf > > > > Both Pavel and I are interested in seeing this come through. So far, > > we mostly do it on volunteer time or as side pieces of other work. > > Pavel's group has good experience with CAN and CAN FD, and with both > > TMS570 and the Zynq (non-MP) boards, with Linux, RTEMS, and NuttX. We > > would be open to collaborating, subject to whatever time or resource > > constraints everyone has :) Michal Lenc has been working on this topic > > as a thesis, "CAN FD Support for Space Grade Real-Time RTEMS > > Executive" Or initial panned target is our own CTU CAN FD IP Core https://canbus.pages.fel.cvut.cz/ which we can test on our MZ_APO Zynq 7k based kits and have emulation for it in QEMU mainline etc... There has been James Holley working on Zynq 7k XCAN support during his intern under Noviumdesigns company funding, if I remember well. But I am not sure if there has been some final version released to public. It has been based on actual RTEMS CAN FIFOs stub and they planned to somehow fix it but if it. If it is offered under RTEMS mainline compatible license then it can be updated to CAN API and FIFOS after rewrite and used for RTEMS XCAN support in the next step. By the way Zynq-MP and Versal have advantage that Xilinx included corresponding CAN FD controllers model into mainline QEMU in CAN subsystem which we have introduced. As for TMS570, it is long time on my interrests list and some models are used in https://www.elektroline.cz company for which I provide consultations. Even when I have been forced to use FreeRTOS for Matlab Rapid Prototyping Platform by former head of the group, I have lead unpaid parallel project which resulted in RTEMS GSoC and integration of TMS570LS3137 BSP into RTEMS mainline. We have not got to work on TMS570LS3137 CAN support for RTEMS, but we have lot of experience with TMS570 CAN in the frame of our HW and SW TMS570 projects for Porsche and EATON including N2HET and DMA full offload of periodic time triggered CAN communication with clock skew and timing automatic adjustment in N2HET code https://dspace.cvut.cz/bitstream/handle/10467/70108/F3-DP-2017-Hofman-Martin-Implementace_casem_rizeneho_planovace_v_distribuovanem_bezpecnostne_kritickem_ridicim_systemu.pdf Unfortunately my attempt to publish this solution as application note has been undermined and even usesfull code attachment to the thesis has been forbidden but people in charge are no longer part of our faculty so even that code could be reused for RTEMS now. > > Regarding LinCAN itself, there is one design challenge to port it, > > which has to do with the use of internal FIFOs already in LinCAN code > > base, or to use RTEMS/POSIX message queue style to interface the CAN > > drivers and userspace. I actually see there are good reasons to > > support both ways, and may explore exactly that. We have had quite > > some discussions here on the topic: > > * https://lists.rtems.org/pipermail/devel/2023-March/074537.html > > * https://lists.rtems.org/pipermail/devel/2022-April/071235.html > > * https://lists.rtems.org/pipermail/devel/2013-April/030761.html (for > > historical good measure) To move project forward, we have decided to start with LinCAN based FIFOs design. It is result/confirmation even from our parallel discussion with Gedare. We can try alternatives later, but use of LinCAN concept as it has been used for many years by more real-time applications in GNU/Linux ecosystems is better to start with. Even that keeping LinCAN as module outside RTEMS would reduce code duplication, I tend to full integration into RTEMS mainline and cleaning code out of all compatibility layers. I.e.: use the LinCAN code as the model for RTEMS native stack. It would make future reuse in other possible environments more difficult, but is the best for RTEMS. We will be happy to cooperate with others on the project and discuss the options and implementation. I expect that we will need to start with initial port/ implementation coding ourselves (planned in the frame of Michal Lenc's theses) and then there will be lot of space to join for others to review, enhance common code and work on individual CAN controllers drivers. There is our local Wiki sandbox for links etc... https://gitlab.fel.cvut.cz/otrees/rtems/work-and-ideas/-/wikis/can_fd but if there is interrest we can move it to https://devel.rtems.org/ even in this stub/initial phase... Best wishes, Pavel Pavel Pisa phone: +420 603531357 e-mail: p...@cmp.felk.cvut.cz Department of Control Engineering FEE CVUT Karlovo namesti 13, 121 35, Prague 2 university: http://control.fel.cvut.cz/ personal: http://cmp.felk.cvut.cz/~pisa company: https://pikron.com/ PiKRON s.r.o. 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