Messages in this thread | | | Subject | Re: [RFC PATCH 1/3] can: m_can: Create m_can core to leverage common code | From | "Rizvi, Mohammad Faiz Abbas" <> | Date | Thu, 10 Jan 2019 13:27:49 +0530 |
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Hi Dan, Wolfgang,
On 1/10/2019 1:14 PM, Wolfgang Grandegger wrote: > Hello Dan, > > sorry for my late response on that topic... > > Am 09.01.19 um 21:58 schrieb Dan Murphy: >> Wolfgang >> >> On 11/3/18 5:45 AM, Wolfgang Grandegger wrote: >>> Hello Dan, >>> >>> Am 31.10.2018 um 21:15 schrieb Dan Murphy: >>>> Wolfgang >>>> >>>> Thanks for the review >>>> >>>> On 10/27/2018 09:19 AM, Wolfgang Grandegger wrote: >>>>> Hello Dan, >>>>> >>>>> for the RFC, could you please just do the necessary changes to the >>>>> existing code. We can discuss about better names, etc. later. For >>>>> the review if the common code I quickly did: >>>>> >>>>> mv m_can.c m_can_platform.c >>>>> mv m_can_core.c m_can.c >>>>> >>>>> The file names are similar to what we have for the C_CAN driver. >>>>> >>>>> s/classdev/priv/ >>>>> variable name s/m_can_dev/priv/ >>>>> >>>>> Then your patch 1/3 looks as shown below. I'm going to comment on that >>>>> one. The comments start with "***".... >>>>> >>>> >>>> So you would like me to align the names with the c_can driver? >>> >>> That would be the obvious choice. >>>> <snip> >>>>> >>>>> *** I didn't review the rest of the patch for now. >>>>> >>>> >>>> snipped the code to reply to the comment. >>>> >>>>> Looking to the generic code, you didn't really change the way >>>>> the driver is accessing the registers. Also the interrupt handling >>>>> and rx polling is as it was before. Does that work properly using >>>>> the SPI interface of the TCAN4x5x? >>>> >>>> I don't want to change any of that yet. Maybe my cover letter was not clear >>>> or did not go through. >>>> >>>> But the intention was just to break out the functionality to create a MCAN framework >>>> that can be used by devices that contain the Bosch MCAN core and provider their own protocal to access >>>> the registers in the device. >>>> >>>> I don't want to do any functional changes at this time on the IP code itself until we have a framework. >>>> There should be no regression in the io mapped code. >>>> >>>> I did comment on the interrupt handling and asked if a threaded work queue would affect CAN timing. >>>> For the original TCAN driver this was the way it was implemented. >>> >>> Do threaded interrupts with RX polling make sense? I think we need a >>> common interface allowing to select hard-irqs+napi or threaded-irqs. >>> >> >> I have been working on this code for about a month now and I am *not happy* with the amount of change that needs >> to be done to make the m_can a framework. >> >> I can tx/rx frames from another CAN device to the TCAN part but I have not even touched the iomapped code. >> >> The challenging part is that the m_can code that is currently available does not have to worry about atomic context because >> there is no peripheral waiting. Since the TCAN is a peripheral device we need to take into about the hard waits in IRQ context >> as well as the atomic context. Doing this creates many deltas in the base code that may break iomapped devices. I have had to >> add the thread_irqs and now I am in the midst of the issue you brought up with napi. I would have to schedule a queue for perp devices >> and leave the non-threaded iomapped irq. >> >> At this point I think it may be wise to leave the m_can code alone as it is working and stable and just work on the TCAN driver as >> a standalone driver. A framework would be nice but I think it would destablize the m_can driver which is embedded in many SoC's and >> we cannot possibly test everyone of them. > > Unfortunately, I do not have m_can hardware at hand.
There are exactly 3 platforms in mainline that use the m_can driver. I can help Dan test it on a dra76x. I haven't had a chance to look at the changes in depth, but just testing for regressions on existing platforms shouldn't be too hard once we have it working on one.
Thanks, Faiz
> >> What are your thoughts? > > What we need is a common set of functions doing tx, rx, error and state > handling. This will requires substantial changes to the existing > io-mapped m_can driver, of course. I still believe it's worth the > effort, but I agree that it's difficult for you to re-write and test the > existing m_can driver. > > What about implementing such a set of common functions plus the SPI > specific part for your TCAN device. What do you/others think? > > Wolfgang. >
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