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Date: Tue, 22 Jun 2021 10:17:46 +0000
From: "Y.b. Lu" <yangbo.lu@....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>,
"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
"mptcp@...ts.linux.dev" <mptcp@...ts.linux.dev>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Mat Martineau <mathew.j.martineau@...ux.intel.com>,
Matthieu Baerts <matthieu.baerts@...sares.net>,
Shuah Khan <shuah@...nel.org>,
Michal Kubecek <mkubecek@...e.cz>,
Florian Fainelli <f.fainelli@...il.com>,
Andrew Lunn <andrew@...n.ch>, Rui Sousa <rui.sousa@....com>,
Sebastien Laveze <sebastien.laveze@....com>
Subject: RE: [net-next, v3, 01/10] ptp: add ptp virtual clock driver framework
Hi Richard,
> -----Original Message-----
> From: Richard Cochran <richardcochran@...il.com>
> Sent: 2021年6月18日 1:33
> To: Y.b. Lu <yangbo.lu@....com>
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> linux-kselftest@...r.kernel.org; mptcp@...ts.linux.dev; David S . Miller
> <davem@...emloft.net>; Jakub Kicinski <kuba@...nel.org>; Mat Martineau
> <mathew.j.martineau@...ux.intel.com>; Matthieu Baerts
> <matthieu.baerts@...sares.net>; Shuah Khan <shuah@...nel.org>; Michal
> Kubecek <mkubecek@...e.cz>; Florian Fainelli <f.fainelli@...il.com>;
> Andrew Lunn <andrew@...n.ch>; Rui Sousa <rui.sousa@....com>; Sebastien
> Laveze <sebastien.laveze@....com>
> Subject: Re: [net-next, v3, 01/10] ptp: add ptp virtual clock driver framework
>
> On Tue, Jun 15, 2021 at 05:45:08PM +0800, Yangbo Lu wrote:
> > diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile index
> > 8673d1743faa..3c6a905760e2 100644
> > --- a/drivers/ptp/Makefile
> > +++ b/drivers/ptp/Makefile
> > @@ -3,7 +3,7 @@
> > # Makefile for PTP 1588 clock support.
> > #
> >
> > -ptp-y := ptp_clock.o ptp_chardev.o ptp_sysfs.o
> > +ptp-y := ptp_clock.o ptp_vclock.o ptp_chardev.o
> ptp_sysfs.o
>
> Nit: Please place ptp_vclock.o at the end of the list.
Ok.
>
> > ptp_kvm-$(CONFIG_X86) := ptp_kvm_x86.o ptp_kvm_common.o
> > ptp_kvm-$(CONFIG_HAVE_ARM_SMCCC) := ptp_kvm_arm.o
> ptp_kvm_common.o
> > obj-$(CONFIG_PTP_1588_CLOCK) += ptp.o
>
> > diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h
> > index 6b97155148f1..3f388d63904c 100644
> > --- a/drivers/ptp/ptp_private.h
> > +++ b/drivers/ptp/ptp_private.h
> > @@ -48,6 +48,20 @@ struct ptp_clock {
> > struct kthread_delayed_work aux_work; };
> >
> > +#define info_to_vclock(d) container_of((d), struct ptp_vclock, info)
> > +#define cc_to_vclock(d) container_of((d), struct ptp_vclock, cc)
> > +#define dw_to_vclock(d) container_of((d), struct ptp_vclock,
> > +refresh_work)
> > +
> > +struct ptp_vclock {
> > + struct ptp_clock *pclock;
> > + struct ptp_clock_info info;
> > + struct ptp_clock *clock;
> > + struct cyclecounter cc;
> > + struct timecounter tc;
> > + spinlock_t lock; /* protects tc/cc */
> > + struct delayed_work refresh_work;
>
> Can we please have a kthread worker here instead of work?
>
> Experience shows that plain work can be delayed for a long, long time on busy
> systems.
>
I think do_aux_work callback could be utilized for ptp virtual clock, right?
> > +};
> > +
> > /*
> > * The function queue_cnt() is safe for readers to call without
> > * holding q->lock. Readers use this function to verify that the
> > queue @@ -89,4 +103,6 @@ extern const struct attribute_group
> > *ptp_groups[]; int ptp_populate_pin_groups(struct ptp_clock *ptp);
> > void ptp_cleanup_pin_groups(struct ptp_clock *ptp);
> >
> > +struct ptp_vclock *ptp_vclock_register(struct ptp_clock *pclock);
> > +void ptp_vclock_unregister(struct ptp_vclock *vclock);
> > #endif
>
> > diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c new
> > file mode 100644 index 000000000000..b8f500677314
> > --- /dev/null
> > +++ b/drivers/ptp/ptp_vclock.c
> > @@ -0,0 +1,154 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * PTP virtual clock driver
> > + *
> > + * Copyright 2021 NXP
> > + */
> > +#include <linux/slab.h>
> > +#include "ptp_private.h"
> > +
> > +#define PTP_VCLOCK_CC_MULT (1 << 31)
> > +#define PTP_VCLOCK_CC_SHIFT 31
>
> These two are okay, but ...
>
> > +#define PTP_VCLOCK_CC_MULT_NUM (1 << 9)
> > +#define PTP_VCLOCK_CC_MULT_DEM 15625ULL
>
> the similarity of naming is confusing for these two. They are only used in
> the .adjfine method. How about this?
>
> PTP_VCLOCK_FADJ_NUMERATOR, or even PTP_VCLOCK_FADJ_SHIFT (see
> below)
> PTP_VCLOCK_FADJ_DENOMINATOR
>
> > +#define PTP_VCLOCK_CC_REFRESH_INTERVAL (HZ * 2)
>
> Consider dropping CC from the name.
> PTP_VCLOCK_REFRESH_INTERVAL sounds good to me.
>
Thanks. Will rename the MACROs per your suggestion.
> > +static int ptp_vclock_adjfine(struct ptp_clock_info *ptp, long
> > +scaled_ppm) {
> > + struct ptp_vclock *vclock = info_to_vclock(ptp);
> > + unsigned long flags;
> > + s64 adj;
> > +
> > + adj = (s64)scaled_ppm * PTP_VCLOCK_CC_MULT_NUM;
>
> Rather than
>
> scaled_ppm * (1 << 9)
>
> I suggest
>
> scaled_ppm << 9
>
> instead. I suppose a good compiler would replace the multiplication with a
> bit shift, but it never hurts to spell it out.
Ok.
>
> > + adj = div_s64(adj, PTP_VCLOCK_CC_MULT_DEM);
> > +
> > + spin_lock_irqsave(&vclock->lock, flags);
> > + timecounter_read(&vclock->tc);
> > + vclock->cc.mult = PTP_VCLOCK_CC_MULT + adj;
> > + spin_unlock_irqrestore(&vclock->lock, flags);
> > +
> > + return 0;
> > +}
>
> Thanks,
> Richard
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