Re: [PATCH v6 3/6] iio: adc: ad7192: Update clock config

Alexandru Ardelean
2024-06-25T05:30:59Z

On Mon, Jun 24, 2024 at 3:50 PM Alisa-Dariana Roman
<alisadariana@gmail.com> wrote:
>

Hello,

A few comments inline.

> There are actually 4 configuration modes of clock source for AD719X
> devices. Either a crystal can be attached externally between MCLK1 and
> MCLK2 pins, or an external CMOS-compatible clock can drive the MCLK2
> pin. The other 2 modes make use of the 4.92MHz internal clock.
>
> Removed properties adi,int-clock-output-enable and adi,clock-xtal were
> undocumented. Use cleaner alternative of configuring external clock by
> using clock names mclk and xtal.

Should we keep the old properties for backwards compatibility?
While I like the new approach, the downside is that someone upgrades
the kernel and may run into issues with their board, because one of
these properties went away.

>
> Removed functionality of AD7192_CLK_INT_CO restored in complementary
> patch.
>
> Signed-off-by: Alisa-Dariana Roman <alisa.roman@analog.com>
> ---
> drivers/iio/adc/ad7192.c | 56 ++++++++++++++++++++--------------------
> 1 file changed, 28 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
> index 334ab90991d4..940517df5429 100644
> --- a/drivers/iio/adc/ad7192.c
> +++ b/drivers/iio/adc/ad7192.c
> @@ -396,25 +396,37 @@ static inline bool ad7192_valid_external_frequency(u32 freq)
> freq <= AD7192_EXT_FREQ_MHZ_MAX);
> }
>
> -static int ad7192_clock_select(struct ad7192_state *st)
> +static const char *const ad7192_clock_names[] = {
> + "xtal",
> + "mclk"

Just a thought; no strong opinion.
Maybe add a short comment about these being "clock_sel" values
AD7192_CLK_EXT_MCLK1_2 & AD7192_CLK_EXT_MCLK2 ?
This is mostly due to the "st->clock_sel = AD7192_CLK_EXT_MCLK1_2 +
ret;" logic (which is fine)
Before, this change, it would

> +};
> +
> +static int ad7192_clock_setup(struct ad7192_state *st)
> {
> struct device *dev = &st->sd.spi->dev;
> - unsigned int clock_sel;
> -
> - clock_sel = AD7192_CLK_INT;
> + int ret;
>
> - /* use internal clock */
> - if (!st->mclk) {
> - if (device_property_read_bool(dev, "adi,int-clock-output-enable"))
> - clock_sel = AD7192_CLK_INT_CO;
> + ret = device_property_match_property_string(dev, "clock-names",
> + ad7192_clock_names,
> + ARRAY_SIZE(ad7192_clock_names));
> + if (ret < 0) {
> + st->clock_sel = AD7192_CLK_INT;
> + st->fclk = AD7192_INT_FREQ_MHZ;

Since this is a new function, an early return can be added here.
This would make the else statement redundant, and the function would
have less indentation.

So, something like:
if (ret < 0) {
st->clock_sel = AD7192_CLK_INT;
st->fclk = AD7192_INT_FREQ_MHZ;
return 0;
}

st->clock_sel = AD7192_CLK_EXT_MCLK1_2 + ret;

st->mclk = devm_clk_get_enabled(dev, ad7192_clock_names[ret]);
if (IS_ERR(st->mclk))
...................

> } else {
> - if (device_property_read_bool(dev, "adi,clock-xtal"))
> - clock_sel = AD7192_CLK_EXT_MCLK1_2;
> - else
> - clock_sel = AD7192_CLK_EXT_MCLK2;
> + st->clock_sel = AD7192_CLK_EXT_MCLK1_2 + ret;
> +
> + st->mclk = devm_clk_get_enabled(dev, ad7192_clock_names[ret]);
> + if (IS_ERR(st->mclk))
> + return dev_err_probe(dev, PTR_ERR(st->mclk),
> + "Failed to get mclk\n");
> +
> + st->fclk = clk_get_rate(st->mclk);
> + if (!ad7192_valid_external_frequency(st->fclk))
> + return dev_err_probe(dev, -EINVAL,
> + "External clock frequency out of bounds\n");
> }
>
> - return clock_sel;
> + return 0;
> }
>
> static int ad7192_setup(struct iio_dev *indio_dev, struct device *dev)
> @@ -1275,21 +1287,9 @@ static int ad7192_probe(struct spi_device *spi)
> if (ret)
> return ret;
>
> - st->fclk = AD7192_INT_FREQ_MHZ;
> -
> - st->mclk = devm_clk_get_optional_enabled(dev, "mclk");
> - if (IS_ERR(st->mclk))
> - return PTR_ERR(st->mclk);
> -
> - st->clock_sel = ad7192_clock_select(st);
> -
> - if (st->clock_sel == AD7192_CLK_EXT_MCLK1_2 ||
> - st->clock_sel == AD7192_CLK_EXT_MCLK2) {
> - st->fclk = clk_get_rate(st->mclk);
> - if (!ad7192_valid_external_frequency(st->fclk))
> - return dev_err_probe(dev, -EINVAL,
> - "External clock frequency out of bounds\n");
> - }
> + ret = ad7192_clock_setup(st);
> + if (ret)
> + return ret;
>
> ret = ad7192_setup(indio_dev, dev);
> if (ret)
> --
> 2.34.1
>
>