target/linux/brcm2708/patches-4.19/950-0524-i2c-bcm2835-Model-Divider-in-CCF.patch

   1 From c86d0f6bfecc53a44e753f14238921ababae29d4 Mon Sep 17 00:00:00 2001
   2 From: Annaliese McDermond <nh6z@nh6z.net>
   3 Date: Sat, 8 Jun 2019 10:14:43 -0700
   4 Subject: [PATCH 524/703] i2c: bcm2835: Model Divider in CCF
   5
   6 Commit bebff81fb8b9216eb4fba22cf910553621ae3477 upstream.
   7
   8 Model the I2C bus clock divider as a part of the Core Clock Framework.
   9 Primarily this removes the clk_get_rate() call from each transfer.
  10 This call causes problems for slave drivers that themselves have
  11 internal clock components that are controlled by an I2C interface.
  12 When the slave's internal clock component is prepared, the prepare
  13 lock is obtained, and it makes calls to the I2C subsystem to
  14 command the hardware to activate the clock.  In order to perform
  15 the I2C transfer, this driver sets the divider, which requires
  16 it to get the parent clock rate, which it does with clk_get_rate().
  17 Unfortunately, this function will try to take the clock prepare
  18 lock, which is already held by the slave's internal clock calls
  19 creating a deadlock.
  20
  21 Modeling the divider in the CCF natively removes this dependency
  22 and the divider value is only set upon changing the bus clock
  23 frequency or changes in the parent clock that cascade down to this
  24 divisor.  This obviates the need to set the divider with every
  25 transfer and avoids the deadlock described above.  It also should
  26 provide better clock debugging and save a few cycles on each
  27 transfer due to not having to recalcuate the divider value.
  28
  29 Signed-off-by: Annaliese McDermond <nh6z@nh6z.net>
  30 Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
  31 Reviewed-by: Eric Anholt <eric@anholt.net>
  32 Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
  33 ---
  34  drivers/i2c/busses/i2c-bcm2835.c | 145 ++++++++++++++++++++++++-------
  35  1 file changed, 114 insertions(+), 31 deletions(-)
  36
  37 --- a/drivers/i2c/busses/i2c-bcm2835.c
  38 +++ b/drivers/i2c/busses/i2c-bcm2835.c
  39 @@ -12,6 +12,8 @@
  40   */
  41
  42  #include <linux/clk.h>
  43 +#include <linux/clkdev.h>
  44 +#include <linux/clk-provider.h>
  45  #include <linux/completion.h>
  46  #include <linux/err.h>
  47  #include <linux/i2c.h>
  48 @@ -71,9 +73,7 @@ struct bcm2835_debug {
  49  struct bcm2835_i2c_dev {
  50         struct device *dev;
  51         void __iomem *regs;
  52 -       struct clk *clk;
  53         int irq;
  54 -       u32 bus_clk_rate;
  55         struct i2c_adapter adapter;
  56         struct completion completion;
  57         struct i2c_msg *curr_msg;
  58 @@ -164,12 +164,17 @@ static inline u32 bcm2835_i2c_readl(stru
  59         return readl(i2c_dev->regs + reg);
  60  }
  61
  62 -static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
  63 +#define to_clk_bcm2835_i2c(_hw) container_of(_hw, struct clk_bcm2835_i2c, hw)
  64 +struct clk_bcm2835_i2c {
  65 +       struct clk_hw hw;
  66 +       struct bcm2835_i2c_dev *i2c_dev;
  67 +};
  68 +
  69 +static int clk_bcm2835_i2c_calc_divider(unsigned long rate,
  70 +                               unsigned long parent_rate)
  71  {
  72 -       u32 divider, redl, fedl;
  73 +       u32 divider = DIV_ROUND_UP(parent_rate, rate);
  74
  75 -       divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
  76 -                              i2c_dev->bus_clk_rate);
  77         /*
  78          * Per the datasheet, the register is always interpreted as an even
  79          * number, by rounding down. In other words, the LSB is ignored. So,
  80 @@ -178,12 +183,23 @@ static int bcm2835_i2c_set_divider(struc
  81         if (divider & 1)
  82                 divider++;
  83         if ((divider < BCM2835_I2C_CDIV_MIN) ||
  84 -           (divider > BCM2835_I2C_CDIV_MAX)) {
  85 -               dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n");
  86 +           (divider > BCM2835_I2C_CDIV_MAX))
  87                 return -EINVAL;
  88 -       }
  89
  90 -       bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
  91 +       return divider;
  92 +}
  93 +
  94 +static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
  95 +                               unsigned long parent_rate)
  96 +{
  97 +       struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
  98 +       u32 redl, fedl;
  99 +       u32 divider = clk_bcm2835_i2c_calc_divider(rate, parent_rate);
 100 +
 101 +       if (divider == -EINVAL)
 102 +               return -EINVAL;
 103 +
 104 +       bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DIV, divider);
 105
 106         /*
 107          * Number of core clocks to wait after falling edge before
 108 @@ -198,12 +214,62 @@ static int bcm2835_i2c_set_divider(struc
 109          */
 110         redl = max(divider / 4, 1u);
 111
 112 -       bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DEL,
 113 +       bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_DEL,
 114                            (fedl << BCM2835_I2C_FEDL_SHIFT) |
 115                            (redl << BCM2835_I2C_REDL_SHIFT));
 116         return 0;
 117  }
 118
 119 +static long clk_bcm2835_i2c_round_rate(struct clk_hw *hw, unsigned long rate,
 120 +                               unsigned long *parent_rate)
 121 +{
 122 +       u32 divider = clk_bcm2835_i2c_calc_divider(rate, *parent_rate);
 123 +
 124 +       return DIV_ROUND_UP(*parent_rate, divider);
 125 +}
 126 +
 127 +static unsigned long clk_bcm2835_i2c_recalc_rate(struct clk_hw *hw,
 128 +                                               unsigned long parent_rate)
 129 +{
 130 +       struct clk_bcm2835_i2c *div = to_clk_bcm2835_i2c(hw);
 131 +       u32 divider = bcm2835_i2c_readl(div->i2c_dev, BCM2835_I2C_DIV);
 132 +
 133 +       return DIV_ROUND_UP(parent_rate, divider);
 134 +}
 135 +
 136 +static const struct clk_ops clk_bcm2835_i2c_ops = {
 137 +       .set_rate = clk_bcm2835_i2c_set_rate,
 138 +       .round_rate = clk_bcm2835_i2c_round_rate,
 139 +       .recalc_rate = clk_bcm2835_i2c_recalc_rate,
 140 +};
 141 +
 142 +static struct clk *bcm2835_i2c_register_div(struct device *dev,
 143 +                                       const char *mclk_name,
 144 +                                       struct bcm2835_i2c_dev *i2c_dev)
 145 +{
 146 +       struct clk_init_data init;
 147 +       struct clk_bcm2835_i2c *priv;
 148 +       char name[32];
 149 +
 150 +       snprintf(name, sizeof(name), "%s_div", dev_name(dev));
 151 +
 152 +       init.ops = &clk_bcm2835_i2c_ops;
 153 +       init.name = name;
 154 +       init.parent_names = (const char* []) { mclk_name };
 155 +       init.num_parents = 1;
 156 +       init.flags = 0;
 157 +
 158 +       priv = devm_kzalloc(dev, sizeof(struct clk_bcm2835_i2c), GFP_KERNEL);
 159 +       if (priv == NULL)
 160 +               return ERR_PTR(-ENOMEM);
 161 +
 162 +       priv->hw.init = &init;
 163 +       priv->i2c_dev = i2c_dev;
 164 +
 165 +       clk_hw_register_clkdev(&priv->hw, "div", dev_name(dev));
 166 +       return devm_clk_register(dev, &priv->hw);
 167 +}
 168 +
 169  static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
 170  {
 171         u32 val;
 172 @@ -363,7 +429,7 @@ static int bcm2835_i2c_xfer(struct i2c_a
 173  {
 174         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
 175         unsigned long time_left;
 176 -       int i, ret;
 177 +       int i;
 178
 179         if (debug)
 180                 i2c_dev->debug_num_msgs = num;
 181 @@ -379,10 +445,6 @@ static int bcm2835_i2c_xfer(struct i2c_a
 182                         return -EOPNOTSUPP;
 183                 }
 184
 185 -       ret = bcm2835_i2c_set_divider(i2c_dev);
 186 -       if (ret)
 187 -               return ret;
 188 -
 189         i2c_dev->curr_msg = msgs;
 190         i2c_dev->num_msgs = num;
 191         reinit_completion(&i2c_dev->completion);
 192 @@ -443,6 +505,9 @@ static int bcm2835_i2c_probe(struct plat
 193         struct resource *mem, *irq;
 194         int ret;
 195         struct i2c_adapter *adap;
 196 +       const char *mclk_name;
 197 +       struct clk *bus_clk;
 198 +       u32 bus_clk_rate;
 199
 200         i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
 201         if (!i2c_dev)
 202 @@ -456,21 +521,6 @@ static int bcm2835_i2c_probe(struct plat
 203         if (IS_ERR(i2c_dev->regs))
 204                 return PTR_ERR(i2c_dev->regs);
 205
 206 -       i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
 207 -       if (IS_ERR(i2c_dev->clk)) {
 208 -               if (PTR_ERR(i2c_dev->clk) != -EPROBE_DEFER)
 209 -                       dev_err(&pdev->dev, "Could not get clock\n");
 210 -               return PTR_ERR(i2c_dev->clk);
 211 -       }
 212 -
 213 -       ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 214 -                                  &i2c_dev->bus_clk_rate);
 215 -       if (ret < 0) {
 216 -               dev_warn(&pdev->dev,
 217 -                        "Could not read clock-frequency property\n");
 218 -               i2c_dev->bus_clk_rate = 100000;
 219 -       }
 220 -
 221         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 222         if (!irq) {
 223                 dev_err(&pdev->dev, "No IRQ resource\n");
 224 @@ -485,6 +535,35 @@ static int bcm2835_i2c_probe(struct plat
 225                 return -ENODEV;
 226         }
 227
 228 +       mclk_name = of_clk_get_parent_name(pdev->dev.of_node, 0);
 229 +
 230 +       bus_clk = bcm2835_i2c_register_div(&pdev->dev, mclk_name, i2c_dev);
 231 +
 232 +       if (IS_ERR(bus_clk)) {
 233 +               dev_err(&pdev->dev, "Could not register clock\n");
 234 +               return PTR_ERR(bus_clk);
 235 +       }
 236 +
 237 +       ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 238 +                                  &bus_clk_rate);
 239 +       if (ret < 0) {
 240 +               dev_warn(&pdev->dev,
 241 +                        "Could not read clock-frequency property\n");
 242 +               bus_clk_rate = 100000;
 243 +       }
 244 +
 245 +       ret = clk_set_rate_exclusive(bus_clk, bus_clk_rate);
 246 +       if (ret < 0) {
 247 +               dev_err(&pdev->dev, "Could not set clock frequency\n");
 248 +               return ret;
 249 +       }
 250 +
 251 +       ret = clk_prepare_enable(bus_clk);
 252 +       if (ret) {
 253 +               dev_err(&pdev->dev, "Couldn't prepare clock");
 254 +               return ret;
 255 +       }
 256 +
 257         adap = &i2c_dev->adapter;
 258         i2c_set_adapdata(adap, i2c_dev);
 259         adap->owner = THIS_MODULE;
 260 @@ -507,6 +586,10 @@ static int bcm2835_i2c_probe(struct plat
 261  static int bcm2835_i2c_remove(struct platform_device *pdev)
 262  {
 263         struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 264 +       struct clk *bus_clk = devm_clk_get(i2c_dev->dev, "div");
 265 +
 266 +       clk_rate_exclusive_put(bus_clk);
 267 +       clk_disable_unprepare(bus_clk);
 268
 269         free_irq(i2c_dev->irq, i2c_dev);
 270         i2c_del_adapter(&i2c_dev->adapter);