target/linux/brcm2708/patches-4.9/950-0112-i2c-bcm2835-Add-support-for-dynamic-clock.patch

   1 From ce8663f1f101f8c7b9037c31269b0b31373737ad Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= <noralf@tronnes.org>
   3 Date: Tue, 27 Sep 2016 01:00:08 +0200
   4 Subject: [PATCH] i2c: bcm2835: Add support for dynamic clock
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 Support a dynamic clock by reading the frequency and setting the
  10 divisor in the transfer function instead of during probe.
  11
  12 Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
  13 Reviewed-by: Martin Sperl <kernel@martin.sperl.org>
  14 ---
  15  drivers/i2c/busses/i2c-bcm2835.c | 51 +++++++++++++++++++++++++---------------
  16  1 file changed, 32 insertions(+), 19 deletions(-)
  17
  18 --- a/drivers/i2c/busses/i2c-bcm2835.c
  19 +++ b/drivers/i2c/busses/i2c-bcm2835.c
  20 @@ -58,6 +58,7 @@ struct bcm2835_i2c_dev {
  21         void __iomem *regs;
  22         struct clk *clk;
  23         int irq;
  24 +       u32 bus_clk_rate;
  25         struct i2c_adapter adapter;
  26         struct completion completion;
  27         struct i2c_msg *curr_msg;
  28 @@ -78,6 +79,30 @@ static inline u32 bcm2835_i2c_readl(stru
  29         return readl(i2c_dev->regs + reg);
  30  }
  31
  32 +static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
  33 +{
  34 +       u32 divider;
  35 +
  36 +       divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
  37 +                              i2c_dev->bus_clk_rate);
  38 +       /*
  39 +        * Per the datasheet, the register is always interpreted as an even
  40 +        * number, by rounding down. In other words, the LSB is ignored. So,
  41 +        * if the LSB is set, increment the divider to avoid any issue.
  42 +        */
  43 +       if (divider & 1)
  44 +               divider++;
  45 +       if ((divider < BCM2835_I2C_CDIV_MIN) ||
  46 +           (divider > BCM2835_I2C_CDIV_MAX)) {
  47 +               dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n");
  48 +               return -EINVAL;
  49 +       }
  50 +
  51 +       bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
  52 +
  53 +       return 0;
  54 +}
  55 +
  56  static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
  57  {
  58         u32 val;
  59 @@ -224,7 +249,7 @@ static int bcm2835_i2c_xfer(struct i2c_a
  60  {
  61         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
  62         unsigned long time_left;
  63 -       int i;
  64 +       int i, ret;
  65
  66         for (i = 0; i < (num - 1); i++)
  67                 if (msgs[i].flags & I2C_M_RD) {
  68 @@ -233,6 +258,10 @@ static int bcm2835_i2c_xfer(struct i2c_a
  69                         return -EOPNOTSUPP;
  70                 }
  71
  72 +       ret = bcm2835_i2c_set_divider(i2c_dev);
  73 +       if (ret)
  74 +               return ret;
  75 +
  76         i2c_dev->curr_msg = msgs;
  77         i2c_dev->num_msgs = num;
  78         reinit_completion(&i2c_dev->completion);
  79 @@ -282,7 +311,6 @@ static int bcm2835_i2c_probe(struct plat
  80  {
  81         struct bcm2835_i2c_dev *i2c_dev;
  82         struct resource *mem, *irq;
  83 -       u32 bus_clk_rate, divider;
  84         int ret;
  85         struct i2c_adapter *adap;
  86
  87 @@ -306,28 +334,13 @@ static int bcm2835_i2c_probe(struct plat
  88         }
  89
  90         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
  91 -                                  &bus_clk_rate);
  92 +                                  &i2c_dev->bus_clk_rate);
  93         if (ret < 0) {
  94                 dev_warn(&pdev->dev,
  95                          "Could not read clock-frequency property\n");
  96 -               bus_clk_rate = 100000;
  97 +               i2c_dev->bus_clk_rate = 100000;
  98         }
  99
 100 -       divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
 101 -       /*
 102 -        * Per the datasheet, the register is always interpreted as an even
 103 -        * number, by rounding down. In other words, the LSB is ignored. So,
 104 -        * if the LSB is set, increment the divider to avoid any issue.
 105 -        */
 106 -       if (divider & 1)
 107 -               divider++;
 108 -       if ((divider < BCM2835_I2C_CDIV_MIN) ||
 109 -           (divider > BCM2835_I2C_CDIV_MAX)) {
 110 -               dev_err(&pdev->dev, "Invalid clock-frequency\n");
 111 -               return -ENODEV;
 112 -       }
 113 -       bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
 114 -
 115         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 116         if (!irq) {
 117                 dev_err(&pdev->dev, "No IRQ resource\n");