netdev - Re: [PATCH v2 1/3] net: mvpp2: tai: add refcount for ptp worker

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Message-ID: <cab62ad6-c495-48f3-91c8-5c27c43582ba@lunn.ch>
Date:   Tue, 18 Apr 2023 02:44:24 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Shmuel Hazan <shmuel.h@...lu.com>
Cc:     Russell King <linux@...linux.org.uk>,
        Marcin Wojtas <mw@...ihalf.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Richard Cochran <richardcochran@...il.com>,
        horatiu.vultur@...rochip.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] net: mvpp2: tai: add refcount for ptp worker

On Mon, Apr 17, 2023 at 08:07:39PM +0300, Shmuel Hazan wrote:
> In some configurations, a single TAI can be responsible for multiple
> mvpp2 interfaces. However, the mvpp2 driver will call mvpp22_tai_stop
> and mvpp22_tai_start per interface RX timestamp disable/enable.
> 
> As a result, disabling timestamping for one interface would stop the
> worker and corrupt the other interface's RX timestamps.
> 
> This commit solves the issue by introducing a simpler ref count for each
> TAI instance.
> 
> Fixes: ce3497e2072e ("net: mvpp2: ptp: add support for receive timestamping")
> Signed-off-by: Shmuel Hazan <shmuel.h@...lu.com>
> ---
>  .../net/ethernet/marvell/mvpp2/mvpp2_tai.c    | 30 ++++++++++++++++---
>  1 file changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c
> index 95862aff49f1..2e3d43b1bac1 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_tai.c
> @@ -61,6 +61,7 @@ struct mvpp2_tai {
>  	u64 period;		// nanosecond period in 32.32 fixed point
>  	/* This timestamp is updated every two seconds */
>  	struct timespec64 stamp;
> +	u16 poll_worker_refcount;
>  };
>  
>  static void mvpp2_tai_modify(void __iomem *reg, u32 mask, u32 set)
> @@ -368,18 +369,39 @@ void mvpp22_tai_tstamp(struct mvpp2_tai *tai, u32 tstamp,
>  	hwtstamp->hwtstamp = timespec64_to_ktime(ts);
>  }
>  
> +static void mvpp22_tai_start_unlocked(struct mvpp2_tai *tai)
> +{
> +	tai->poll_worker_refcount++;
> +	if (tai->poll_worker_refcount > 1)
> +		return;
> +
> +	ptp_schedule_worker(tai->ptp_clock, 0);

So the old code used to have delay here, not 0. And delay would be
returned by mvpp22_tai_aux_work() and have a value of 2000ms. So this
is a clear change in behaviour. Why is it O.K. not to delay for 2
seconds?  Should you actually still have the delay, pass it as a
parameter into this function?

     Andrew