target/linux/generic/patches-3.3/861-04_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 --- a/drivers/spi/spi-gpio.c
   8 +++ b/drivers/spi/spi-gpio.c
   9 @@ -22,6 +22,7 @@
  10  #include <linux/init.h>
  11  #include <linux/platform_device.h>
  12  #include <linux/gpio.h>
  13 +#include <linux/delay.h>
  14
  15  #include <linux/spi/spi.h>
  16  #include <linux/spi/spi_bitbang.h>
  17 @@ -70,6 +71,7 @@ struct spi_gpio {
  18   *             #define SPI_MOSI_GPIO   120
  19   *             #define SPI_SCK_GPIO    121
  20   *             #define SPI_N_CHIPSEL   4
  21 + *             #undef NEED_SPIDELAY
  22   *             #include "spi-gpio.c"
  23   */
  24
  25 @@ -77,6 +79,7 @@ struct spi_gpio {
  26  #define DRIVER_NAME    "spi_gpio"
  27
  28  #define GENERIC_BITBANG        /* vs tight inlines */
  29 +#define NEED_SPIDELAY  1
  30
  31  /* all functions referencing these symbols must define pdata */
  32  #define SPI_MISO_GPIO  ((pdata)->miso)
  33 @@ -121,12 +124,20 @@ static inline int getmiso(const struct s
  34  #undef pdata
  35
  36  /*
  37 - * NOTE:  this clocks "as fast as we can".  It "should" be a function of the
  38 - * requested device clock.  Software overhead means we usually have trouble
  39 - * reaching even one Mbit/sec (except when we can inline bitops), so for now
  40 - * we'll just assume we never need additional per-bit slowdowns.
  41 + * NOTE:  to clock "as fast as we can", set spi_device.max_speed_hz
  42 + * and spi_transfer.speed_hz to 0.
  43 + * Otherwise this is a function of the requested device clock.
  44 + * Software overhead means we usually have trouble
  45 + * reaching even one Mbit/sec (except when we can inline bitops). So on small
  46 + * embedded devices with fast SPI slaves you usually don't need a delay.
  47   */
  48 -#define spidelay(nsecs)        do {} while (0)
  49 +static inline void spidelay(unsigned nsecs)
  50 +{
  51 +#ifdef NEED_SPIDELAY
  52 +       if (unlikely(nsecs))
  53 +               ndelay(nsecs);
  54 +#endif /* NEED_SPIDELAY */
  55 +}
  56
  57  #include "spi-bitbang-txrx.h"
  58