Re: [PATCH net-next v5 2/2] net: phy: broadcom: Add PTP support for some Broadcom PHYs.

From: Flugsvamp <jlemon@flugsvamp.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: Jonathan Lemon <jonathan.lemon@gmail.com>,
	netdev@vger.kernel.org, f.fainelli@gmail.com, andrew@lunn.ch,
	hkallweit1@gmail.com, linux@armlinux.org.uk,
	bcm-kernel-feedback-list@broadcom.com, kernel-team@fb.com,
	davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com,
	edumazet@google.com
Subject: Re: [PATCH net-next v5 2/2] net: phy: broadcom: Add PTP support for some Broadcom PHYs.
Date: Mon, 30 May 2022 18:15:44 -0700	[thread overview]
Message-ID: <57926B53-BB8B-4A9B-9340-0DFFDA4452BA@flugsvamp.com> (raw)
In-Reply-To: <20220530230439.GA22405@hoboy.vegasvil.org>

> On May 30, 2022, at 4:04 PM, Richard Cochran <richardcochran@gmail.com> wrote:
> 
> On Mon, May 30, 2022 at 10:07:44AM -0700, Jonathan Lemon wrote:
>>> On Sat, May 28, 2022 at 05:34:47PM -0700, Richard Cochran wrote:
>>>> On Wed, May 18, 2022 at 03:39:35PM -0700, Jonathan Lemon wrote:
>>> 
>>>> +static int bcm_ptp_adjtime_locked(struct bcm_ptp_private *priv,
>>>> +                  s64 delta_ns)
>>>> +{
>>>> +    struct timespec64 ts;
>>>> +    int err;
>>>> +
>>>> +    err = bcm_ptp_gettime_locked(priv, &ts, NULL);
>>>> +    if (!err) {
>>>> +        set_normalized_timespec64(&ts, ts.tv_sec,
>>>> +                      ts.tv_nsec + delta_ns);
>>> 
>>> This also takes a LONG time when delta is large...
>> 
>> Didn't we just go through this?  What constitutes a "large" offset here?
>> The current version seems acceptable to me:
> 
> When the PHY boots, it starts from time zero.
> 
> Then as a client it needs to adjust to today, something like:
> 
> 1653951762.413809006 or Mon May 30 16:02:42 2022
> 
> (that means adding 1,653,951,762,413,809,006 nanoseconds)
> 
> Try that and see how long it takes to apply the adjustment.

That’s certainly a big adjustment. I was expecting something along the lines of a settime() call, followed up by adjtime().

Will fix. Seems like there should be a better call sequence for this, though. 

Sent from my iPhone