linux-kernel - Re: [PATCH v2 net-next 1/3] ptp: Add adjphase function to support phase offset control.

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Message-ID: <228ceba4-47a8-49ef-994a-fe898cdc7fc1@nvidia.com>
Date:   Thu, 4 Aug 2022 14:40:25 +0300
From:   Aya Levin <ayal@...dia.com>
To:     vincent.cheng.xh@...esas.com, richardcochran@...il.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 net-next 1/3] ptp: Add adjphase function to support
 phase offset control.



On 5/2/2020 6:35 AM, vincent.cheng.xh@...esas.com wrote:
> From: Vincent Cheng <vincent.cheng.xh@...esas.com>
> 
> Adds adjust phase function to take advantage of a PHC
> clock's hardware filtering capability that uses phase offset
> control word instead of frequency offset control word.
> 
> Signed-off-by: Vincent Cheng <vincent.cheng.xh@...esas.com>
> ---
>   drivers/ptp/ptp_clock.c          | 3 +++
>   include/linux/ptp_clock_kernel.h | 6 +++++-
>   2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c
> index acabbe7..fc984a8 100644
> --- a/drivers/ptp/ptp_clock.c
> +++ b/drivers/ptp/ptp_clock.c
> @@ -146,6 +146,9 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
>   		else
>   			err = ops->adjfreq(ops, ppb);
>   		ptp->dialed_frequency = tx->freq;
> +	} else if (tx->modes & ADJ_OFFSET) {
> +		if (ops->adjphase)
> +			err = ops->adjphase(ops, tx->offset);
>   	} else if (tx->modes == 0) {
>   		tx->freq = ptp->dialed_frequency;
>   		err = 0;
> diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
> index 121a7ed..31144d9 100644
> --- a/include/linux/ptp_clock_kernel.h
> +++ b/include/linux/ptp_clock_kernel.h
> @@ -36,7 +36,7 @@ struct ptp_system_timestamp {
>   };
>   
>   /**
> - * struct ptp_clock_info - decribes a PTP hardware clock
> + * struct ptp_clock_info - describes a PTP hardware clock
>    *
>    * @owner:     The clock driver should set to THIS_MODULE.
>    * @name:      A short "friendly name" to identify the clock and to
> @@ -65,6 +65,9 @@ struct ptp_system_timestamp {
>    *            parameter delta: Desired frequency offset from nominal frequency
>    *            in parts per billion
>    *
> + * @adjphase:  Adjusts the phase offset of the hardware clock.
> + *             parameter delta: Desired change in nanoseconds.
> + *
>    * @adjtime:  Shifts the time of the hardware clock.
>    *            parameter delta: Desired change in nanoseconds.
>    *
> @@ -128,6 +131,7 @@ struct ptp_clock_info {
>   	struct ptp_pin_desc *pin_config;
>   	int (*adjfine)(struct ptp_clock_info *ptp, long scaled_ppm);
>   	int (*adjfreq)(struct ptp_clock_info *ptp, s32 delta);
> +	int (*adjphase)(struct ptp_clock_info *ptp, s32 phase);
Hi,

Please explain the difference in the output between adjphase and 
adjtime. I'd expect both to add delta to current time. Am I missing 
something?

Thanks,
Aya
>   	int (*adjtime)(struct ptp_clock_info *ptp, s64 delta);
>   	int (*gettime64)(struct ptp_clock_info *ptp, struct timespec64 *ts);
>   	int (*gettimex64)(struct ptp_clock_info *ptp, struct timespec64 *ts,