target/linux/generic-2.6/patches-2.6.28/920-04-spi-gpio-implement-spi-delay.patch

   1 Implement the SPI-GPIO delay function for busses that need speed limitation.
   2
   3 --mb
   4
   5
   6
   7 Index: linux-2.6.28.5/drivers/spi/spi_gpio.c
   8 ===================================================================
   9 --- linux-2.6.28.5.orig/drivers/spi/spi_gpio.c  2009-02-15 18:53:47.000000000 +0100
  10 +++ linux-2.6.28.5/drivers/spi/spi_gpio.c       2009-02-15 19:08:58.000000000 +0100
  11 @@ -21,6 +21,7 @@
  12  #include <linux/init.h>
  13  #include <linux/platform_device.h>
  14  #include <linux/gpio.h>
  15 +#include <linux/delay.h>
  16
  17  #include <linux/spi/spi.h>
  18  #include <linux/spi/spi_bitbang.h>
  19 @@ -69,6 +70,7 @@ struct spi_gpio {
  20   *             #define SPI_MOSI_GPIO   120
  21   *             #define SPI_SCK_GPIO    121
  22   *             #define SPI_N_CHIPSEL   4
  23 + *             #undef NEED_SPIDELAY
  24   *             #include "spi_gpio.c"
  25   */
  26
  27 @@ -76,6 +78,7 @@ struct spi_gpio {
  28  #define DRIVER_NAME    "spi_gpio"
  29
  30  #define GENERIC_BITBANG        /* vs tight inlines */
  31 +#define NEED_SPIDELAY  1
  32
  33  /* all functions referencing these symbols must define pdata */
  34  #define SPI_MISO_GPIO  ((pdata)->miso)
  35 @@ -120,12 +123,20 @@ static inline int getmiso(const struct s
  36  #undef pdata
  37
  38  /*
  39 - * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
  40 - * requested device clock.  Software overhead means we usually have trouble
  41 - * reaching even one Mbit/sec (except when we can inline bitops), so for now
  42 - * we'll just assume we never need additional per-bit slowdowns.
  43 + * NOTE:  to clock "as fast as we can", set spi_device.max_speed_hz
  44 + * and spi_transfer.speed_hz to 0.
  45 + * Otherwise this is a function of the requested device clock.
  46 + * Software overhead means we usually have trouble
  47 + * reaching even one Mbit/sec (except when we can inline bitops). So on small
  48 + * embedded devices with fast SPI slaves you usually don't need a delay.
  49   */
  50 -#define spidelay(nsecs)        do {} while (0)
  51 +static inline void spidelay(unsigned nsecs)
  52 +{
  53 +#ifdef NEED_SPIDELAY
  54 +       if (unlikely(nsecs))
  55 +               ndelay(nsecs);
  56 +#endif /* NEED_SPIDELAY */
  57 +}
  58
  59  #define        EXPAND_BITBANG_TXRX
  60  #include <linux/spi/spi_bitbang.h>