Re: [PATCH v3 1/4] i2c: rk3x: switch to i2c generic dt parsing

From: Andy Shevchenko
Date: Thu Jan 14 2016 - 08:05:25 EST


On Thu, Jan 14, 2016 at 2:31 PM, David Wu <david.wu@xxxxxxxxxxxxxx> wrote:
> Switch to the new generic functions: i2c_parse_fw_timings().

Nice one!
Reviwed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>

Minor comments below.

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

> @@ -437,10 +434,7 @@ out:
> * Calculate divider values for desired SCL frequency
> *
> * @clk_rate: I2C input clock rate
> - * @scl_rate: Desired SCL rate
> - * @scl_rise_ns: How many ns it takes for SCL to rise.
> - * @scl_fall_ns: How many ns it takes for SCL to fall.
> - * @sda_fall_ns: How many ns it takes for SDA to fall.
> + * @t_input: Known I2C timing information.

Perhaps t_input -> t.

> * @div_low: Divider output for low
> * @div_high: Divider output for high
> *
> @@ -448,11 +442,10 @@ out:
> * 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, unsigned long scl_rate,
> - unsigned long scl_rise_ns,
> - unsigned long scl_fall_ns,
> - unsigned long sda_fall_ns,
> - unsigned long *div_low, unsigned long *div_high)
> +static int rk3x_i2c_calc_divs(unsigned long clk_rate,
> + struct i2c_timings *t_input,

Ditto.

> + unsigned long *div_low,
> + unsigned long *div_high)
> {
> unsigned long spec_min_low_ns, spec_min_high_ns;
> unsigned long spec_setup_start, spec_max_data_hold_ns;

> @@ -517,18 +510,19 @@ static int rk3x_i2c_calc_divs(unsigned long clk_rate, unsigned long scl_rate,
> * we meet tSU;STA and tHD;STA times.
> */
> min_high_ns = max(min_high_ns,
> - DIV_ROUND_UP((scl_rise_ns + spec_setup_start) * 1000, 875));
> + DIV_ROUND_UP((t_input->scl_rise_ns + spec_setup_start) * 1000,
> + 875));

To one line (after above change).

> min_high_ns = max(min_high_ns,
> - DIV_ROUND_UP((scl_rise_ns + spec_setup_start +
> - sda_fall_ns + spec_min_high_ns), 2));
> + DIV_ROUND_UP((t_input->scl_rise_ns + spec_setup_start +
> + t_input->sda_fall_ns + spec_min_high_ns), 2));

Ditto.

> @@ -620,10 +614,8 @@ static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
> u64 t_low_ns, t_high_ns;
> int ret;
>
> - ret = rk3x_i2c_calc_divs(clk_rate, i2c->scl_frequency, i2c->scl_rise_ns,
> - i2c->scl_fall_ns, i2c->sda_fall_ns,
> - &div_low, &div_high);
> - WARN_ONCE(ret != 0, "Could not reach SCL freq %u", i2c->scl_frequency);
> + ret = rk3x_i2c_calc_divs(clk_rate, &i2c->t, &div_low, &div_high);
> + WARN_ONCE(ret != 0, "Could not reach SCL freq %u", i2c->t.bus_freq_hz);

I would recommend to

struct i2c_timings *t = &i2c->t;

+ ret = rk3x_i2c_calc_divs(clk_rate, t, &div_low, &div_high);
+ WARN_ONCE(ret != 0, "Could not reach SCL freq %u", t->bus_freq_hz);

> @@ -634,7 +626,7 @@ static void rk3x_i2c_adapt_div(struct rk3x_i2c *i2c, unsigned long clk_rate)
> dev_dbg(i2c->dev,
> "CLK %lukhz, Req %uns, Act low %lluns high %lluns\n",
> clk_rate / 1000,
> - 1000000000 / i2c->scl_frequency,
> + 1000000000 / i2c->t.bus_freq_hz,

Ditto.

--
With Best Regards,
Andy Shevchenko