lkml.org 
[lkml]   [2012]   [Jan]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRE: RFC: usb: musb: Adding CPPI4.1 DMA driver under drivers/dma
    Date
    Hi,
    > On 01/13/2012 01:40 PM, Gupta, Ajay Kumar wrote:
    >
    > > CPPI4.1 (Communication Port Programming Interface) is a TI specific
    > DMA
    > > controller used in multiple TI platform such as AM33x, DA8x, AM35x,
    > TI81x.
    > > The DMA engine is mainly used by musb controller on above platform.
    >
    > There are (at least out of tree) platforms using CPPI 4.1 for
    > Ethernet.
    >
    > > Earlier version of the driver was submitted by Sergei Shtylyov at [1]
    > but
    > > was not merged due to disagreement on the location of driver in
    > kernel.
    >
    > To be precise, TI requested pulling out already queued (to
    > arch/arm/common/)
    > CPPI 4.1 driver from RMK's patch system without even notifying me. At
    > least that
    > was RMK's version...
    >
    > > Refer the discussions at [1] for more details.
    >
    > > [1] http://marc.info/?l=linux-usb&m=125087318308323
    >
    > Unfortunately, that's not all of the discussion of interest.
    >
    > > The new implementation of the CPPI4.1 DMA slave driver will be in the
    > > drivers/dma folder, complying to dmaengine framework.
    >
    > Has there been any work in this direction done yet?

    Currently we are working on design flow and API details which will be posted
    first for review.

    Ajay
    >
    > > It would involve changes in existing musb driver also for which
    > current
    > > plan is to maintain the compatibility of non-CPPI4.1 DMA in musb
    > driver.
    >
    > I didn't quite understand this part...
    >
    > > The task is planned to be spitted into below subtasks.
    >
    > > (1) Post RFC on the API details, changes envisaged in musb driver and
    > other
    > > challenges
    >
    > First of all, I foresee changes in drivers/dma/ to cope with the
    > entity in
    > CPPI 4.1 called the queue manager (there's also buffer manager but it
    > wasn't
    > implemented on DA8xx, so I didn't design any API for it).
    >
    > > (2) Implement and post RFC for the CPPI4.1 DMA driver and changes
    > needed in
    > > musb driver.
    >
    > > Let me know if you have any thoughts/comments on this.
    >
    > > Regards,
    > > Ajay
    >
    > WBR, Sergei



    \
     
     \ /
      Last update: 2012-01-16 11:59    [W:0.027 / U:88.744 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site