lkml.org 
[lkml]   [2010]   [May]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH] ad7877: keep dma rx buffers in seperate cache lines
    On Thu, May 6, 2010 at 06:37, Oskar Schirmer wrote:
    >  struct ser_req {
    > +       u16                     sample;
    > +       char                    __padalign[L1_CACHE_BYTES - sizeof(u16)];
    > +
    >        u16                     reset;
    >        u16                     ref_on;
    >        u16                     command;
    > -       u16                     sample;
    >        struct spi_message      msg;
    >        struct spi_transfer     xfer[6];
    >  };

    are you sure this is necessary ? ser_req is only ever used with
    spi_sync() and it's allocated/released on the fly, so how could
    anything be reading that memory between the start of the transmission
    and the return to adi7877 ?

    >  struct ad7877 {
    > +       u16                     conversion_data[AD7877_NR_SENSE];
    > +       char                    __padalign[L1_CACHE_BYTES
    > +                                       - AD7877_NR_SENSE * sizeof(u16)];
    > +
    >        struct input_dev        *input;
    >        char                    phys[32];
    >
    > @@ -182,8 +188,6 @@ struct ad7877 {
    >        u8                      averaging;
    >        u8                      pen_down_acc_interval;
    >
    > -       u16                     conversion_data[AD7877_NR_SENSE];
    > -
    >        struct spi_transfer     xfer[AD7877_NR_SENSE + 2];
    >        struct spi_message      msg;

    i can see the spi_message inside of this struct being a problem
    because the spi transfer is doing asynchronously with spi_async().
    however, i would add a comment right above these two fields with a
    short explanation as to why they're at the start and why the pad
    exists so someone down the line doesnt move it.
    -mike
    \
     
     \ /
      Last update: 2010-05-06 20:49    [W:0.026 / U:119.196 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site