linux-kernel - RE: [PATCH net 2/2] ptp: idt82p33: implement double dco time correction

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Date:   Thu, 24 Jun 2021 14:40:52 +0000
From:   Min Li <min.li.xe@...esas.com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net 2/2] ptp: idt82p33: implement double dco time
 correction


> -----Original Message-----
> From: Richard Cochran <richardcochran@...il.com>
> Sent: June 23, 2021 11:44 PM
> To: Min Li <min.li.xe@...esas.com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH net 2/2] ptp: idt82p33: implement double dco time
> correction
> 
> On Wed, Jun 23, 2021 at 10:46:25AM -0400, min.li.xe@...esas.com wrote:
> > +static int idt82p33_start_ddco(struct idt82p33_channel *channel, s32
> > +delta_ns) {
> > +	s32 current_ppm = channel->current_freq;
> > +	u32 duration_ms = MSEC_PER_SEC;
> 
> What happens if user space makes a new adjustment before this completes?
> 
> After all, some PTP profiles update the clock several times per second.
> 
> Thanks,
> Richard

Hi Richard

In that case, adjtime would simply return without doing anything as in

@@ -848,11 +914,15 @@ static int idt82p33_adjtime(struct ptp_clock_info *ptp, s64 delta_ns)
 	struct idt82p33 *idt82p33 = channel->idt82p33;
 	int err;
 
+	if (channel->ddco == true)
+		return 0;
+