Re: [PATCH v3 2/4] i2c: rk3x: add ops to caculate i2c clocks

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On Thu, Jan 14, 2016 at 2:31 PM, David Wu <david.wu@xxxxxxxxxxxxxx> wrote:
> From: David Wu <wdc@xxxxxxxxxxxxxx>
>
> I2c Controller of rk3x is updated for the rules to caculate clocks.
> So it need a new method to caculate i2c clock timing information
> for new version. The current method is defined as v0, and new is
> v1, next maybe v2......

Thanks for an update. My comments below.

> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c

> @@ -90,10 +95,27 @@ struct rk3x_i2c_soc_data {
>         int grf_offset;
>  };
>
> +/**
> + * struct rk3x_priv_i2c_timings - rk3x I2C timing information
> + * @div_low: Divider output for low
> + * @div_high: Divider output for high
> + */
> +struct rk3x_priv_i2c_timings {
> +       unsigned long div_low;
> +       unsigned long div_high;
> +};
> +
> +struct rk3x_i2c_ops {
> +       int (*calc_clock)(unsigned long,
> +                         struct i2c_timings *,
> +                         struct rk3x_priv_i2c_timings *);
> +};
> +
>  struct rk3x_i2c {
>         struct i2c_adapter adap;
>         struct device *dev;
>         struct rk3x_i2c_soc_data *soc_data;
> +       struct rk3x_i2c_ops ops;

Not much sense for now to have a struct for one member.

>
>         /* Hardware resources */
>         void __iomem *regs;
> @@ -102,6 +124,7 @@ struct rk3x_i2c {
>

What about
      /* I2C timing settings */
      struct i2c_timings t;

      /* Divider settings */
      int (*calc_divs)(unsigned long,
                        struct i2c_timings *,
                        unsigned long *div_low,
                        unsigned long *div_high);
      unsigned long div_low;
      unsigned long div_high;
?

As far as I understand you still calculate divider values.

>
>         /* Synchronization & notification */
>         spinlock_t lock;
> @@ -431,21 +454,20 @@ out:
>  }
>
>  /**
> - * Calculate divider values for desired SCL frequency
> + * Calculate timing clock info values for desired SCL frequency
>   *
>   * @clk_rate: I2C input clock rate
> - * @t_input: Known I2C timing information.
> - * @div_low: Divider output for low
> - * @div_high: Divider output for high

For now seems better to leave this prototype.

> + * @t_input: Known I2C timing information
> + * @t_output: Caculated rk3x private timing information that would
> + * be written into regs
>   *
>   * Returns: 0 on success, -EINVAL if the goal SCL rate is too slow. In that case
>   * a best-effort divider value is returned in divs. If the target rate is
>   * too high, we silently use the highest possible rate.
>   */
> -static int rk3x_i2c_calc_divs(unsigned long clk_rate,
> -                             struct i2c_timings *t_input,
> -                             unsigned long *div_low,
> -                             unsigned long *div_high)
> +static int rk3x_i2c_v0_calc_clock(unsigned long clk_rate,
> +                                 struct i2c_timings *t_input,
> +                                 struct rk3x_priv_i2c_timings *t_output)
>  {
>         unsigned long spec_min_low_ns, spec_min_high_ns;
>         unsigned long spec_setup_start, spec_max_data_hold_ns;


> @@ -583,25 +605,25 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate,
>
>                 /* Give low the "ideal" and give high whatever extra is left */
>                 extra_low_div = ideal_low_div - min_low_div;
> -               *div_low = ideal_low_div;
> -               *div_high = min_high_div + (extra_div - extra_low_div);
> +               t_output->div_low = ideal_low_div;
> +               t_output->div_high = min_high_div + (extra_div - extra_low_div);
>         }
>
>         /*
>          * Adjust to the fact that the hardware has an implicit "+1".
>          * NOTE: Above calculations always produce div_low > 0 and div_high > 0.
>          */
> -       *div_low = *div_low - 1;
> -       *div_high = *div_high - 1;
> +       t_output->div_low = t_output->div_low - 1;

-= 1

> +       t_output->div_high = t_output->div_high - 1;

Ditto.

But without change of prototype those no needed.

>
>         /* Maximum divider supported by hw is 0xffff */
> -       if (*div_low > 0xffff) {
> -               *div_low = 0xffff;
> +       if (t_output->div_low > 0xffff) {
> +               t_output->div_low = 0xffff;
>                 ret = -EINVAL;
>         }
>
> -       if (*div_high > 0xffff) {
> -               *div_high = 0xffff;
> +       if (t_output->div_high > 0xffff) {
> +               t_output->div_high = 0xffff;
>                 ret = -EINVAL;
>         }
>
> @@ -610,19 +632,21 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate,
>
>  static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
>  {
> -       unsigned long div_low, div_high;
>         u64 t_low_ns, t_high_ns;
>         int ret;
>
> -       ret = rk3x_i2c_calc_divs(clk_rate, &i2c->t, &div_low, &div_high);
> +       ret = i2c->ops.calc_clock(clk_rate, &i2c->t, &i2c->t_priv);
>         WARN_ONCE(ret != 0, "Could not reach SCL freq %u", i2c->t.bus_freq_hz);
>
>         clk_enable(i2c->clk);
> -       i2c_writel(i2c, (div_high << 16) | (div_low & 0xffff), REG_CLKDIV);
> +       i2c_writel(i2c, (i2c->t_priv.div_high << 16) |
> +                 (i2c->t_priv.div_low & 0xffff), REG_CLKDIV);
>         clk_disable(i2c->clk);
>
> -       t_low_ns = div_u64(((u64)div_low + 1) * 8 * 1000000000, clk_rate);
> -       t_high_ns = div_u64(((u64)div_high + 1) * 8 * 1000000000, clk_rate);
> +       t_low_ns = div_u64(((u64)i2c->t_priv.div_low + 1) * 8 * 1000000000,
> +                          clk_rate);
> +       t_high_ns = div_u64(((u64)i2c->t_priv.div_high + 1) * 8 * 1000000000,
> +                           clk_rate);
>         dev_dbg(i2c->dev,
>                 "CLK %lukhz, Req %uns, Act low %lluns high %lluns\n",
>                 clk_rate / 1000,
> @@ -652,12 +676,11 @@ static int rk3x_i2c_clk_notifier_cb(struct notifier_block *nb, unsigned long
>  {
>         struct clk_notifier_data *ndata = data;
>         struct rk3x_i2c *i2c = container_of(nb, struct rk3x_i2c, clk_rate_nb);
> -       unsigned long div_low, div_high;
>
>         switch (event) {
>         case PRE_RATE_CHANGE:
> -               if (rk3x_i2c_calc_divs(ndata->new_rate, &i2c->t,
> -                                      &div_low, &div_high) != 0)
> +               if (i2c->ops.calc_clock(ndata->new_rate, &i2c->t,
> +                                       &i2c->t_priv) != 0)
>                         return NOTIFY_STOP;
>
>                 /* scale up */
> @@ -861,6 +884,7 @@ static int rk3x_i2c_probe(struct platform_device *pdev)
>         u32 value;
>         int irq;
>         unsigned long clk_rate;
> +       unsigned int version;

No need to have a separate variable…

> +       version = (readl(i2c->regs + REG_CON) & VERSION_MASK) >> VERSION_SHIFT;
> +       if (version == RK3X_I2C_V0)
> +               i2c->ops.calc_clock = rk3x_i2c_v0_calc_clock;

value = readl(i2c->regs + REG_CON);
if ((value & VERSION_MASK) >> VERSION_SHIFT) == RK3X_I2C_V0)
  i2c->ops.calc_clock = rk3x_i2c_v0_calc_clock;

-- 
With Best Regards,
Andy Shevchenko
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