target/linux/ar71xx/patches-3.3/200-spi-ath79-add-delay-between-SCK-changes.patch

   1 From cbb3ade4765bc715b5c2eae4a7b6eaf3ff7ad958 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 28/34] 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 |   44 +++++++++++++++++++++++++++++++++++++++++++-
  16  1 files changed, 43 insertions(+), 1 deletions(-)
  17
  18 --- a/drivers/spi/spi-ath79.c
  19 +++ b/drivers/spi/spi-ath79.c
  20 @@ -24,17 +24,24 @@
  21  #include <linux/spi/spi_bitbang.h>
  22  #include <linux/bitops.h>
  23  #include <linux/gpio.h>
  24 +#include <linux/clk.h>
  25 +#include <linux/err.h>
  26
  27  #include <asm/mach-ath79/ar71xx_regs.h>
  28  #include <asm/mach-ath79/ath79_spi_platform.h>
  29
  30  #define DRV_NAME       "ath79-spi"
  31
  32 +#define ATH79_SPI_RRW_DELAY_FACTOR     12000
  33 +#define MHZ                            (1000 * 1000)
  34 +
  35  struct ath79_spi {
  36         struct spi_bitbang      bitbang;
  37         u32                     ioc_base;
  38         u32                     reg_ctrl;
  39         void __iomem            *base;
  40 +       struct clk              *clk;
  41 +       unsigned                rrw_delay;
  42  };
  43
  44  static inline u32 ath79_spi_rr(struct ath79_spi *sp, unsigned reg)
  45 @@ -52,6 +59,12 @@ static inline struct ath79_spi *ath79_sp
  46         return spi_master_get_devdata(spi->master);
  47  }
  48
  49 +static inline void ath79_spi_delay(struct ath79_spi *sp, unsigned nsecs)
  50 +{
  51 +       if (nsecs > sp->rrw_delay)
  52 +               ndelay(nsecs - sp->rrw_delay);
  53 +}
  54 +
  55  static void ath79_spi_chipselect(struct spi_device *spi, int is_active)
  56  {
  57         struct ath79_spi *sp = ath79_spidev_to_sp(spi);
  58 @@ -184,7 +197,9 @@ static u32 ath79_spi_txrx_mode0(struct s
  59
  60                 /* setup MSB (to slave) on trailing edge */
  61                 ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out);
  62 +               ath79_spi_delay(sp, nsecs);
  63                 ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out | AR71XX_SPI_IOC_CLK);
  64 +               ath79_spi_delay(sp, nsecs);
  65
  66                 word <<= 1;
  67         }
  68 @@ -198,6 +213,7 @@ static __devinit int ath79_spi_probe(str
  69         struct ath79_spi *sp;
  70         struct ath79_spi_platform_data *pdata;
  71         struct resource *r;
  72 +       unsigned long rate;
  73         int ret;
  74
  75         master = spi_alloc_master(&pdev->dev, sizeof(*sp));
  76 @@ -239,12 +255,36 @@ static __devinit int ath79_spi_probe(str
  77                 goto err_put_master;
  78         }
  79
  80 +       sp->clk = clk_get(&pdev->dev, "ahb");
  81 +       if (IS_ERR(sp->clk)) {
  82 +               ret = PTR_ERR(sp->clk);
  83 +               goto err_unmap;
  84 +       }
  85 +
  86 +       ret = clk_enable(sp->clk);
  87 +       if (ret)
  88 +               goto err_clk_put;
  89 +
  90 +       rate = DIV_ROUND_UP(clk_get_rate(sp->clk), MHZ);
  91 +       if (!rate) {
  92 +               ret = -EINVAL;
  93 +               goto err_clk_disable;
  94 +       }
  95 +
  96 +       sp->rrw_delay = ATH79_SPI_RRW_DELAY_FACTOR / rate;
  97 +       dev_dbg(&pdev->dev, "register read/write delay is %u nsecs\n",
  98 +               sp->rrw_delay);
  99 +
 100         ret = spi_bitbang_start(&sp->bitbang);
 101         if (ret)
 102 -               goto err_unmap;
 103 +               goto err_clk_disable;
 104
 105         return 0;
 106
 107 +err_clk_disable:
 108 +       clk_disable(sp->clk);
 109 +err_clk_put:
 110 +       clk_put(sp->clk);
 111  err_unmap:
 112         iounmap(sp->base);
 113  err_put_master:
 114 @@ -259,6 +299,8 @@ static __devexit int ath79_spi_remove(st
 115         struct ath79_spi *sp = platform_get_drvdata(pdev);
 116
 117         spi_bitbang_stop(&sp->bitbang);
 118 +       clk_disable(sp->clk);
 119 +       clk_put(sp->clk);
 120         iounmap(sp->base);
 121         platform_set_drvdata(pdev, NULL);
 122         spi_master_put(sp->bitbang.master);