target/linux/ar71xx/patches-3.3/201-spi-ath79-add-delay-between-SCK-changes.patch

   1 From 48b7e765e6e097d20d809fadd17a4355d26ad6d5 Mon Sep 17 00:00:00 2001
   2 From: Gabor Juhos <juhosg@openwrt.org>
   3 Date: Wed, 11 Jan 2012 20:06:35 +0100
   4 Subject: [PATCH 1/7] spi/ath79: add delay between SCK changes
   5
   6 The driver uses the "as fast as it can" approach
   7 to drive the SCK signal. However this does not
   8 work with certain low speed SPI chips (e.g. the
   9 PCF2123 RTC chip). Add per-bit slowdowns in order
  10 to be able to use  the driver with such chips as
  11 well.
  12
  13 Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
  14 ---
  15  drivers/spi/spi-ath79.c |    8 ++++++++
  16  1 files changed, 8 insertions(+), 0 deletions(-)
  17
  18 --- a/drivers/spi/spi-ath79.c
  19 +++ b/drivers/spi/spi-ath79.c
  20 @@ -52,6 +52,12 @@ static inline struct ath79_spi *ath79_sp
  21         return spi_master_get_devdata(spi->master);
  22  }
  23
  24 +static inline void ath79_spi_delay(unsigned nsecs)
  25 +{
  26 +       if (nsecs)
  27 +               ndelay(nsecs);
  28 +}
  29 +
  30  static void ath79_spi_chipselect(struct spi_device *spi, int is_active)
  31  {
  32         struct ath79_spi *sp = ath79_spidev_to_sp(spi);
  33 @@ -184,7 +190,9 @@ static u32 ath79_spi_txrx_mode0(struct s
  34
  35                 /* setup MSB (to slave) on trailing edge */
  36                 ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out);
  37 +               ath79_spi_delay(nsecs);
  38                 ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out | AR71XX_SPI_IOC_CLK);
  39 +               ath79_spi_delay(nsecs);
  40
  41                 word <<= 1;
  42         }