netdev - Re: [PATCH v2 1/1] net: fec: ptp: avoid register access when ipg clock is disabled

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Message-ID: <CAEyMn7aijecc6ai5YaaHFa1Y7u52v=KEga3nRKvXE3o-mCQLYA@mail.gmail.com>
Date:   Fri, 26 Feb 2021 08:22:50 +0100
From:   Heiko Thiery <heiko.thiery@...il.com>
To:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Fugang Duan <fugang.duan@....com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH v2 1/1] net: fec: ptp: avoid register access when ipg
 clock is disabled

Hi all,

Am Do., 25. Feb. 2021 um 22:15 Uhr schrieb Heiko Thiery
<heiko.thiery@...il.com>:
>
> When accessing the timecounter register on an i.MX8MQ the kernel hangs.
> This is only the case when the interface is down. This can be reproduced
> by reading with 'phc_ctrl eth0 get'.
>
> Like described in the change in 91c0d987a9788dcc5fe26baafd73bf9242b68900
> the igp clock is disabled when the interface is down and leads to a
> system hang.
>
> So we check if the ptp clock status before reading the timecounter
> register.
>
> Signed-off-by: Heiko Thiery <heiko.thiery@...il.com>


Sorry for the noise. But just realized that I sent a v3 version of the
patch but forgot to update the subject line (still v2). Should I
resend it with the correct subject?

> ---
> v2:
>  - add mutex (thanks to Richard)
>
> v3:
> I did a mistake and did not test properly
>  - add parenteses
>  - fix the used variable
>
>  drivers/net/ethernet/freescale/fec_ptp.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/net/ethernet/freescale/fec_ptp.c b/drivers/net/ethernet/freescale/fec_ptp.c
> index 2e344aada4c6..1753807cbf97 100644
> --- a/drivers/net/ethernet/freescale/fec_ptp.c
> +++ b/drivers/net/ethernet/freescale/fec_ptp.c
> @@ -377,9 +377,16 @@ static int fec_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
>         u64 ns;
>         unsigned long flags;
>
> +       mutex_lock(&adapter->ptp_clk_mutex);
> +       /* Check the ptp clock */
> +       if (!adapter->ptp_clk_on) {
> +               mutex_unlock(&adapter->ptp_clk_mutex);
> +               return -EINVAL;
> +       }
>         spin_lock_irqsave(&adapter->tmreg_lock, flags);
>         ns = timecounter_read(&adapter->tc);
>         spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
> +       mutex_unlock(&adapter->ptp_clk_mutex);
>
>         *ts = ns_to_timespec64(ns);
>
> --
> 2.30.0
>