target/linux/ar71xx/patches-3.8/001-spi-ath79-add-delay-between-SCK-changes.patch

   1 From 486c150478777ef53cfef6f0d46840b9406b0612 Mon Sep 17 00:00:00 2001
   2 From: Gabor Juhos <juhosg@openwrt.org>
   3 Date: Thu, 27 Dec 2012 10:42:24 +0100
   4 Subject: [PATCH] spi/ath79: add delay between SCK changes
   5
   6 commit 440114fdb13cbc53ea734bcc05b86bcf5b1e430c upstream.
   7
   8 The driver uses the "as fast as it can" approach
   9 to drive the SCK signal. However this does not
  10 work with certain low speed SPI chips (e.g. the
  11 PCF2123 RTC chip).
  12
  13 The patch adds per-bit slowdowns in order to be
  14 able to use the driver with such chips as well.
  15
  16 Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
  17 Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
  18 ---
  19  drivers/spi/spi-ath79.c |   44 +++++++++++++++++++++++++++++++++++++++++++-
  20  1 file changed, 43 insertions(+), 1 deletion(-)
  21
  22 --- a/drivers/spi/spi-ath79.c
  23 +++ b/drivers/spi/spi-ath79.c
  24 @@ -24,17 +24,24 @@
  25  #include <linux/spi/spi_bitbang.h>
  26  #include <linux/bitops.h>
  27  #include <linux/gpio.h>
  28 +#include <linux/clk.h>
  29 +#include <linux/err.h>
  30
  31  #include <asm/mach-ath79/ar71xx_regs.h>
  32  #include <asm/mach-ath79/ath79_spi_platform.h>
  33
  34  #define DRV_NAME       "ath79-spi"
  35
  36 +#define ATH79_SPI_RRW_DELAY_FACTOR     12000
  37 +#define MHZ                            (1000 * 1000)
  38 +
  39  struct ath79_spi {
  40         struct spi_bitbang      bitbang;
  41         u32                     ioc_base;
  42         u32                     reg_ctrl;
  43         void __iomem            *base;
  44 +       struct clk              *clk;
  45 +       unsigned                rrw_delay;
  46  };
  47
  48  static inline u32 ath79_spi_rr(struct ath79_spi *sp, unsigned reg)
  49 @@ -52,6 +59,12 @@ static inline struct ath79_spi *ath79_sp
  50         return spi_master_get_devdata(spi->master);
  51  }
  52
  53 +static inline void ath79_spi_delay(struct ath79_spi *sp, unsigned nsecs)
  54 +{
  55 +       if (nsecs > sp->rrw_delay)
  56 +               ndelay(nsecs - sp->rrw_delay);
  57 +}
  58 +
  59  static void ath79_spi_chipselect(struct spi_device *spi, int is_active)
  60  {
  61         struct ath79_spi *sp = ath79_spidev_to_sp(spi);
  62 @@ -184,7 +197,9 @@ static u32 ath79_spi_txrx_mode0(struct s
  63
  64                 /* setup MSB (to slave) on trailing edge */
  65                 ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out);
  66 +               ath79_spi_delay(sp, nsecs);
  67                 ath79_spi_wr(sp, AR71XX_SPI_REG_IOC, out | AR71XX_SPI_IOC_CLK);
  68 +               ath79_spi_delay(sp, nsecs);
  69
  70                 word <<= 1;
  71         }
  72 @@ -198,6 +213,7 @@ static int ath79_spi_probe(struct platfo
  73         struct ath79_spi *sp;
  74         struct ath79_spi_platform_data *pdata;
  75         struct resource *r;
  76 +       unsigned long rate;
  77         int ret;
  78
  79         master = spi_alloc_master(&pdev->dev, sizeof(*sp));
  80 @@ -236,12 +252,36 @@ static int ath79_spi_probe(struct platfo
  81                 goto err_put_master;
  82         }
  83
  84 +       sp->clk = clk_get(&pdev->dev, "ahb");
  85 +       if (IS_ERR(sp->clk)) {
  86 +               ret = PTR_ERR(sp->clk);
  87 +               goto err_unmap;
  88 +       }
  89 +
  90 +       ret = clk_enable(sp->clk);
  91 +       if (ret)
  92 +               goto err_clk_put;
  93 +
  94 +       rate = DIV_ROUND_UP(clk_get_rate(sp->clk), MHZ);
  95 +       if (!rate) {
  96 +               ret = -EINVAL;
  97 +               goto err_clk_disable;
  98 +       }
  99 +
 100 +       sp->rrw_delay = ATH79_SPI_RRW_DELAY_FACTOR / rate;
 101 +       dev_dbg(&pdev->dev, "register read/write delay is %u nsecs\n",
 102 +               sp->rrw_delay);
 103 +
 104         ret = spi_bitbang_start(&sp->bitbang);
 105         if (ret)
 106 -               goto err_unmap;
 107 +               goto err_clk_disable;
 108
 109         return 0;
 110
 111 +err_clk_disable:
 112 +       clk_disable(sp->clk);
 113 +err_clk_put:
 114 +       clk_put(sp->clk);
 115  err_unmap:
 116         iounmap(sp->base);
 117  err_put_master:
 118 @@ -256,6 +296,8 @@ static int ath79_spi_remove(struct platf
 119         struct ath79_spi *sp = platform_get_drvdata(pdev);
 120
 121         spi_bitbang_stop(&sp->bitbang);
 122 +       clk_disable(sp->clk);
 123 +       clk_put(sp->clk);
 124         iounmap(sp->base);
 125         platform_set_drvdata(pdev, NULL);
 126         spi_master_put(sp->bitbang.master);