Re: [PATCH v2 2/2] iio: frequency: adf4350: add clk provider

["Nuno Sá" <noname.nuno@gmail.com>]

On Fri, 2024-06-07 at 12:57 +0300, Antoniu Miclaus wrote:
> Add clk provider feature for the adf4350.
> 
> Even though the driver was sent as an IIO driver in most cases the
> device is actually seen as a clock provider.
> 
> This patch aims to cover actual usecases requested by users in order to
> completely control the output frequencies from userspace.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
> changes in v2:
>  - rework commit title
>  drivers/iio/frequency/adf4350.c | 129 ++++++++++++++++++++++++++++++++
>  1 file changed, 129 insertions(+)
> 
> diff --git a/drivers/iio/frequency/adf4350.c b/drivers/iio/frequency/adf4350.c
> index 4abf80f75ef5..1eb8bce71fe1 100644
> --- a/drivers/iio/frequency/adf4350.c
> +++ b/drivers/iio/frequency/adf4350.c
> @@ -19,6 +19,7 @@
>  #include <linux/gpio/consumer.h>
>  #include <asm/div64.h>
>  #include <linux/clk.h>
> +#include <linux/clk-provider.h>
>  
>  #include <linux/iio/iio.h>
>  #include <linux/iio/sysfs.h>
> @@ -31,11 +32,21 @@ enum {
>  	ADF4350_PWRDOWN,
>  };
>  
> +struct adf4350_output {
> +	struct clk_hw hw;
> +	struct iio_dev *indio_dev;
> +};
> +
> +#define to_output(_hw) container_of(_hw, struct adf4350_output, hw)
> +
>  struct adf4350_state {
>  	struct spi_device		*spi;
>  	struct gpio_desc		*lock_detect_gpiod;
>  	struct adf4350_platform_data	*pdata;
>  	struct clk			*clk;
> +	struct clk			*clkout;
> +	const char			*clk_out_name;
> +	struct adf4350_output		output;
>  	unsigned long			clkin;
>  	unsigned long			chspc; /* Channel Spacing */
>  	unsigned long			fpfd; /* Phase Frequency Detector */
> @@ -264,6 +275,10 @@ static ssize_t adf4350_write(struct iio_dev *indio_dev,
>  	mutex_lock(&st->lock);
>  	switch ((u32)private) {
>  	case ADF4350_FREQ:
> +		if (st->clkout) {
> +			ret = clk_set_rate(st->clkout, readin);
> +			break;
> +		}
>  		ret = adf4350_set_freq(st, readin);
>  		break;
>  	case ADF4350_FREQ_REFIN:
> @@ -381,6 +396,115 @@ static const struct iio_info adf4350_info = {
>  	.debugfs_reg_access = &adf4350_reg_access,
>  };
>  
> +static void adf4350_clk_del_provider(void *data)
> +{
> +	struct adf4350_state *st = data;
> +
> +	of_clk_del_provider(st->spi->dev.of_node);
> +}
> +
> +static unsigned long adf4350_clk_recalc_rate(struct clk_hw *hw,
> +					     unsigned long parent_rate)
> +{
> +	struct iio_dev *indio_dev = to_output(hw)->indio_dev;
> +	struct adf4350_state *st = iio_priv(indio_dev);
> +	unsigned long long tmp;
> +
> +	tmp = (u64)(st->r0_int * st->r1_mod + st->r0_fract) * st->fpfd;
> +	do_div(tmp, st->r1_mod * (1 << st->r4_rf_div_sel));
> +
> +	return tmp;
> +}
> +
> +static int adf4350_clk_set_rate(struct clk_hw *hw,
> +				unsigned long rate,
> +				unsigned long parent_rate)
> +{
> +	struct iio_dev *indio_dev = to_output(hw)->indio_dev;
> +	struct adf4350_state *st = iio_priv(indio_dev);
> +
> +	if (parent_rate == 0 || parent_rate > ADF4350_MAX_FREQ_REFIN)
> +		return -EINVAL;
> +
> +	st->clkin = parent_rate;
> +
> +	return adf4350_set_freq(st, rate);
> +}
> +
> +static int adf4350_clk_prepare(struct clk_hw *hw)
> +{
> +	struct iio_dev *indio_dev = to_output(hw)->indio_dev;
> +	struct adf4350_state *st = iio_priv(indio_dev);
> +
> +	st->regs[ADF4350_REG2] &= ~ADF4350_REG2_POWER_DOWN_EN;
> +
> +	return adf4350_sync_config(st);
> +}
> +
> +static void adf4350_clk_unprepare(struct clk_hw *hw)
> +{
> +	struct iio_dev *indio_dev = to_output(hw)->indio_dev;
> +	struct adf4350_state *st = iio_priv(indio_dev);
> +
> +	st->regs[ADF4350_REG2] |= ADF4350_REG2_POWER_DOWN_EN;
> +
> +	adf4350_sync_config(st);
> +}
> +
> +static int adf4350_clk_is_enabled(struct clk_hw *hw)
> +{
> +	struct iio_dev *indio_dev = to_output(hw)->indio_dev;
> +	struct adf4350_state *st = iio_priv(indio_dev);
> +
> +	return (st->regs[ADF4350_REG2] & ADF4350_REG2_POWER_DOWN_EN);
> +}
> +
> +static const struct clk_ops adf4350_clk_ops = {
> +	.recalc_rate = adf4350_clk_recalc_rate,
> +	.set_rate = adf4350_clk_set_rate,
> +	.prepare = adf4350_clk_prepare,
> +	.unprepare = adf4350_clk_unprepare,
> +	.is_enabled = adf4350_clk_is_enabled,
> +};
> +
> +static int adf4350_clk_register(struct adf4350_state *st)
> +{
> +	struct spi_device *spi = st->spi;
> +	struct clk_init_data init;
> +	struct clk *clk;
> +	const char *parent_name;
> +	int ret;
> +
> +	if (!device_property_present(&spi->dev, "#clock-cells"))
> +		return 0;
> +
> +	init.name = devm_kasprintf(&spi->dev, GFP_KERNEL, "%s-clk",
> +				   fwnode_get_name(dev_fwnode(&spi->dev)));
> +	device_property_read_string(&spi->dev, "clock-output-names",
> +				    &init.name);
> +
> +	parent_name = of_clk_get_parent_name(spi->dev.of_node, 0);
> +	if (!parent_name)
> +		return -EINVAL;
> +
> +	init.ops = &adf4350_clk_ops;
> +	init.parent_names = &parent_name;
> +	init.num_parents = 1;
> +
> +	st->output.hw.init = &init;
> +	clk = devm_clk_register(&spi->dev, &st->output.hw);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	ret = of_clk_add_provider(spi->dev.of_node, of_clk_src_simple_get,
> clk);
> +	if (ret)
> +		return ret;
> +

I totally agree this chip should be a clock provider (maybe it should even in
drivers/clk from the beginning) but there's one thing that comes to my mind.
Should we still expose the IIO userspace interface in case we register it as a
clock provider?

Sure, we do have clk notifiers in the kernel but I still think it's a sensible
question :)

I suspect we have another "outliers" in drivers/iio/frequency :)

- Nuno Sá