lkml.org 
[lkml]   [2022]   [Mar]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRe: [PATCH v2 2/2] spi: fsl-spi: Implement trailing bits
    Date


    Le 28/02/2022 à 17:14, Mark Brown a écrit :
    > On Mon, Feb 28, 2022 at 04:02:30PM +0000, Christophe Leroy wrote:
    >> Le 28/02/2022 à 16:29, Mark Brown a écrit :
    >
    >>> The binding looks good now but this is still driver specific code when
    >>> it looks like it could easily be implemented in the core - like I said
    >>> on the previous version you'd need to update drivers to advertise less
    >>> than 8 bits but there's basically nothing driver specific I can see here
    >>> so any driver using transfer_one() would get support that way.
    >
    >> Argh ! Sorry your comment to the previous version ended up in Junk
    >> mails. I see it now.
    >
    > No problem.
    >
    >> We discussed that back in 2016 in
    >> https://lore.kernel.org/linux-spi/20160824112701.GE22076@sirena.org.uk/
    >> and my understanding at that time was that it was not something that
    >> could be done at core level.
    >
    >> But maybe things have changed since then ?
    >
    > What I said then was "it would need a new core feature" which is what
    > the binding does, I'm suggesting that you also do that for the handling
    > of the implementation as well.
    >
    > Actually now I think about it perhaps this shouldn't be a binding at all
    > but rather something specified by the client driver - presumably any
    > system using an affected device is going to need these extra clock
    > cycles so they'll all need to add the same property.
    >
    >> By the way, fsl-spi driver doesn't implement transfer_one() but
    >> transfer_one_message() so it takes care of the chipselect changes and
    >> therefore the final dummy transfer with CS off is to be done there as
    >> far as I understand.
    >
    >> Would it mean changing fsl-spi driver to implement transfer_one() first ?
    >
    > Well, if it can implement transfer_one() without any negative
    > consequences whichh

    Seems like your sentence is truncated.

    My understanding today is that this trailing transfer with chipselect
    OFF is to be added at the end of transfer_one_message().

    It can be implemented in the core transfer_one_message() for drivers
    implementing transfer_one(). For the other drivers not having
    transfer_one() but having transfer_one_message(), it must be implemented
    in the driver's transfer_one_message().

    Am I right ?


    fsl-spi driver is the one I need to support this new functionnality and
    it has its own transfer_one_message().

    What would you expect ?


    Thanks
    Christophe
    \
     
     \ /
      Last update: 2022-03-01 13:55    [W:4.742 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site