linux-kernel - Re: [PATCH] net: macb: Fix ptp time adjustment for large negative delta

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Message-ID: <ff8fac12-b5a1-5e2d-e4f6-4ee68bf685a7@microchip.com>
Date:   Wed, 20 Jun 2018 16:04:17 +0200
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     Harini Katakam <harini.katakam@...inx.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <michal.simek@...inx.com>, <harinikatakamlinux@...il.com>,
        Claudiu Beznea - M18063 <Claudiu.Beznea@...rochip.com>
Subject: Re: [PATCH] net: macb: Fix ptp time adjustment for large negative
 delta

On 20/06/2018 at 13:34, Harini Katakam wrote:
> When delta passed to gem_ptp_adjtime is negative, the sign is
> maintained in the ns_to_timespec64 conversion. Hence timespec_add
> should be used directly. timespec_sub will just subtract the negative
> value thus increasing the time difference.
> 
> Signed-off-by: Harini Katakam <harini.katakam@...inx.com>

Makes sense:
Acked-by: Nicolas Ferre <nicolas.ferre@...rochip.com>

> ---
>   drivers/net/ethernet/cadence/macb_ptp.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_ptp.c b/drivers/net/ethernet/cadence/macb_ptp.c
> index 2220c77..6788351 100644
> --- a/drivers/net/ethernet/cadence/macb_ptp.c
> +++ b/drivers/net/ethernet/cadence/macb_ptp.c
> @@ -170,10 +170,7 @@ static int gem_ptp_adjtime(struct ptp_clock_info *ptp, s64 delta)
>   
>   	if (delta > TSU_NSEC_MAX_VAL) {
>   		gem_tsu_get_time(&bp->ptp_clock_info, &now);
> -		if (sign)
> -			now = timespec64_sub(now, then);
> -		else
> -			now = timespec64_add(now, then);
> +		now = timespec64_add(now, then);
>   
>   		gem_tsu_set_time(&bp->ptp_clock_info,
>   				 (const struct timespec64 *)&now);
> 


-- 
Nicolas Ferre