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From: Richard Cochran <richardcochran@gmail.com>
To: Yangbo Lu <yangbo.lu@nxp.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, mptcp@lists.linux.dev,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Mat Martineau <mathew.j.martineau@linux.intel.com>,
	Matthieu Baerts <matthieu.baerts@tessares.net>,
	Shuah Khan <shuah@kernel.org>, Michal Kubecek <mkubecek@suse.cz>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Andrew Lunn <andrew@lunn.ch>, Rui Sousa <rui.sousa@nxp.com>,
	Sebastien Laveze <sebastien.laveze@nxp.com>
Subject: Re: [net-next, v3, 01/10] ptp: add ptp virtual clock driver framework
Date: Thu, 17 Jun 2021 19:32:38 +0200	[thread overview]
Message-ID: <20210617173237.GA4770@localhost> (raw)
In-Reply-To: <20210615094517.48752-2-yangbo.lu@nxp.com>

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.

>  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.

> +};
> +
>  /*
>   * 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.

> +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.

> +	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

  reply	other threads:[~2021-06-17 17:32 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-15  9:45 [net-next, v3, 00/10] ptp: support virtual clocks and timestamping Yangbo Lu
2021-06-15  9:45 ` [net-next, v3, 01/10] ptp: add ptp virtual clock driver framework Yangbo Lu
2021-06-17 17:32   ` Richard Cochran [this message]
2021-06-22 10:17     ` Y.b. Lu
2021-06-15  9:45 ` [net-next, v3, 02/10] ptp: support ptp physical/virtual clocks conversion Yangbo Lu
2021-06-17 17:42   ` Richard Cochran
2021-06-22 10:18     ` Y.b. Lu
2021-06-17 18:27   ` Richard Cochran
2021-06-22 10:35     ` Y.b. Lu
2021-06-25 11:09       ` Y.b. Lu
2021-06-19  4:06   ` Richard Cochran
2021-06-22 10:39     ` Y.b. Lu
2021-06-15  9:45 ` [net-next, v3, 03/10] ptp: track available ptp vclocks information Yangbo Lu
2021-06-15  9:45 ` [net-next, v3, 04/10] ptp: add kernel API ptp_get_vclocks_index() Yangbo Lu
2021-06-15  9:45 ` [net-next, v3, 05/10] ethtool: add a new command for getting PHC virtual clocks Yangbo Lu
2021-06-15 19:49   ` Jakub Kicinski
2021-06-22 10:10     ` Y.b. Lu
2021-06-15 23:24   ` Michal Kubecek
2021-06-22 10:10     ` Y.b. Lu
2021-06-15  9:45 ` [net-next, v3, 06/10] ptp: add kernel API ptp_convert_timestamp() Yangbo Lu
2021-06-15  9:45 ` [net-next, v3, 07/10] net: sock: extend SO_TIMESTAMPING for PHC binding Yangbo Lu
2021-06-16  1:00   ` Mat Martineau
2021-06-22 10:14     ` Y.b. Lu
2021-06-16 10:27   ` kernel test robot
2021-06-16 10:39   ` kernel test robot
2021-06-15  9:45 ` [net-next, v3, 08/10] net: socket: support hardware timestamp conversion to PHC bound Yangbo Lu
2021-06-15  9:45 ` [net-next, v3, 09/10] selftests/net: timestamping: support binding PHC Yangbo Lu
2021-06-15  9:45 ` [net-next, v3, 10/10] MAINTAINERS: add entry for PTP virtual clock driver Yangbo Lu

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