Re: [RFC PATCH] i2c: refactor parsing of timings

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Mar 26, 2020 at 11:16:47AM +0100, Wolfram Sang wrote:
> When I wanted to print the chosen values to debug output, I concluded
> that a helper function to parse one timing would be helpful.
> 
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
> 
> I am not entirely happy because 'dev' and 'u' is the same for each call.
> Then again, we can't use a for-loop over an array of parameters, because
> some default values depend on previously obtained timings.
> 
> Looking for opinions here...

No objections. (We may bikeshed about namings, though)

However, looking into the code, I would go a bit further (perhaps as a separate
change) and export parsing of clock-frequency, because tons of drivers only
need one property, i.e. clock-frequency out of firmware.

> 
>  drivers/i2c/i2c-core-base.c | 78 ++++++++++++++++++-------------------
>  1 file changed, 38 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 474baaf8c9e7..60b0aa246af2 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -1609,6 +1609,18 @@ void i2c_del_adapter(struct i2c_adapter *adap)
>  }
>  EXPORT_SYMBOL(i2c_del_adapter);
>  
> +static void i2c_parse_timing(struct device *dev, char *prop_name, u32 *cur_val_p,
> +			    u32 def_val, bool use_def)
> +{
> +	int ret;
> +
> +	ret = device_property_read_u32(dev, prop_name, cur_val_p);
> +	if (ret && use_def)
> +		*cur_val_p = def_val;
> +
> +	dev_dbg(dev, "%s: %u\n", prop_name, *cur_val_p);
> +}
> +
>  /**
>   * i2c_parse_fw_timings - get I2C related timing parameters from firmware
>   * @dev: The device to scan for I2C timing properties
> @@ -1627,49 +1639,35 @@ EXPORT_SYMBOL(i2c_del_adapter);
>   */
>  void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults)
>  {
> -	int ret;
> -
> -	ret = device_property_read_u32(dev, "clock-frequency", &t->bus_freq_hz);
> -	if (ret && use_defaults)
> -		t->bus_freq_hz = I2C_MAX_STANDARD_MODE_FREQ;
> -
> -	ret = device_property_read_u32(dev, "i2c-scl-rising-time-ns", &t->scl_rise_ns);
> -	if (ret && use_defaults) {
> -		if (t->bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ)
> -			t->scl_rise_ns = 1000;
> -		else if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
> -			t->scl_rise_ns = 300;
> -		else
> -			t->scl_rise_ns = 120;
> -	}
> -
> -	ret = device_property_read_u32(dev, "i2c-scl-falling-time-ns", &t->scl_fall_ns);
> -	if (ret && use_defaults) {
> -		if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
> -			t->scl_fall_ns = 300;
> -		else
> -			t->scl_fall_ns = 120;
> -	}
> +	bool u = use_defaults;
> +	u32 d;
>  
> -	ret = device_property_read_u32(dev, "i2c-scl-internal-delay-ns", &t->scl_int_delay_ns);
> -	if (ret && use_defaults)
> -		t->scl_int_delay_ns = 0;
> +	i2c_parse_timing(dev, "clock-frequency", &t->bus_freq_hz,
> +			 I2C_MAX_STANDARD_MODE_FREQ, u);
>  
> -	ret = device_property_read_u32(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns);
> -	if (ret && use_defaults)
> -		t->sda_fall_ns = t->scl_fall_ns;
> -
> -	ret = device_property_read_u32(dev, "i2c-sda-hold-time-ns", &t->sda_hold_ns);
> -	if (ret && use_defaults)
> -		t->sda_hold_ns = 0;
> -
> -	ret = device_property_read_u32(dev, "i2c-digital-filter-width-ns", &t->digital_filter_width_ns);
> -	if (ret && use_defaults)
> -		t->digital_filter_width_ns = 0;
> +	if (t->bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ)
> +		d = 1000;
> +	else if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
> +		d = 300;
> +	else
> +		d = 120;
> +	i2c_parse_timing(dev, "i2c-scl-rising-time-ns", &t->scl_rise_ns, d, u);
>  
> -	ret = device_property_read_u32(dev, "i2c-analog-filter-cutoff-frequency", &t->analog_filter_cutoff_freq_hz);
> -	if (ret && use_defaults)
> -		t->analog_filter_cutoff_freq_hz = 0;
> +	if (t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ)
> +		d = 300;
> +	else
> +		d = 120;
> +	i2c_parse_timing(dev, "i2c-scl-falling-time-ns", &t->scl_fall_ns, d, u);
> +
> +	i2c_parse_timing(dev, "i2c-scl-internal-delay-ns",
> +			 &t->scl_int_delay_ns, 0, u);
> +	i2c_parse_timing(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns,
> +			 t->scl_fall_ns, u);
> +	i2c_parse_timing(dev, "i2c-sda-hold-time-ns", &t->sda_hold_ns, 0, u);
> +	i2c_parse_timing(dev, "i2c-digital-filter-width-ns",
> +			 &t->digital_filter_width_ns, 0, u);
> +	i2c_parse_timing(dev, "i2c-analog-filter-cutoff-frequency",
> +			 &t->analog_filter_cutoff_freq_hz, 0, u);
>  }
>  EXPORT_SYMBOL_GPL(i2c_parse_fw_timings);
>  
> -- 
> 2.20.1
> 

-- 
With Best Regards,
Andy Shevchenko