Re: [PATCH 09/19] clk: at91: sckc: register slow_rc with accuracy option

Claudiu.Beznea
2020-07-15T15:39:39Z

On 15.07.2020 14:24, Claudiu Beznea wrote:
> Register slow rc with accuracy option.
>
> Fixes: 04bcc4275e601 ("clk: at91: sckc: add support for SAM9X60")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
> ---
> drivers/clk/at91/sckc.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/at91/sckc.c b/drivers/clk/at91/sckc.c
> index 15dc4cd86d76..2d65770d8665 100644
> --- a/drivers/clk/at91/sckc.c
> +++ b/drivers/clk/at91/sckc.c
> @@ -471,8 +471,9 @@ static void __init of_sam9x60_sckc_setup(struct device_node *np)
> if (!regbase)
> return;
>
> - slow_rc = clk_hw_register_fixed_rate(NULL, parent_names[0], NULL, 0,
> - 32768);
> + slow_rc = clk_hw_register_fixed_rate_with_accuracy(NULL, parent_names[0],
> + NULL, 0, 32768,
> + 93750000);

I forgot to mention in commit message (I'll do it in v2 once I'll
gather more comments on this series):

Chapter 57.7.5 of SAM9X60 datasheet specifies that the maximum drift of
this oscillator is +- 3KHz. I used that value and the formula at [1]
or the calculator at [2] to compute the PPB value.

[1] https://www.everythingrf.com/rf-calculators/ppm-to-hz-calculator
[2] https://www.changpuak.ch/electronics/ppm_to_Hz_converter.php

Thank you,
Claudiu Beznea

> if (IS_ERR(slow_rc))
> return;
>
>