linux-kernel - Re: [PATCH] net: macb: ensure the device is available before accessing GEMGXL control registers

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Message-ID: <CANXhq0rQqeGO_LM233bB8Kg5XD_Q7xrtOhVrYeuCxXj29N3+Rg@mail.gmail.com>
Date:   Sat, 22 May 2021 17:08:44 +0800
From:   Zong Li <zong.li@...ive.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     nicolas.ferre@...rochip.com, claudiu.beznea@...rochip.com,
        davem@...emloft.net, kuba@...nel.org,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Andreas Schwab <schwab@...ux-m68k.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Michael Turquette <mturquette@...libre.com>,
        geert@...ux-m68k.org, Yixun Lan <yixun.lan@...il.com>,
        netdev@...r.kernel.org,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>
Subject: Re: [PATCH] net: macb: ensure the device is available before
 accessing GEMGXL control registers

On Sat, May 22, 2021 at 12:51 AM Florian Fainelli <f.fainelli@...il.com> wrote:
>
>
>
> On 5/21/2021 5:48 AM, Zong Li wrote:
> > If runtime power menagement is enabled, the gigabit ethernet PLL would
> > be disabled after macb_probe(). During this period of time, the system
> > would hang up if we try to access GEMGXL control registers.
> >
> > We can't put runtime_pm_get/runtime_pm_put/ there due to the issue of
> > sleep inside atomic section (7fa2955ff70ce453 ("sh_eth: Fix sleeping
> > function called from invalid context"). Add the similar flag to ensure
> > the device is available before accessing GEMGXL device.
> >
> > Signed-off-by: Zong Li <zong.li@...ive.com>
> > ---
> >  drivers/net/ethernet/cadence/macb.h      | 2 ++
> >  drivers/net/ethernet/cadence/macb_main.c | 7 +++++++
> >  2 files changed, 9 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> > index d8d87213697c..acf5242ce715 100644
> > --- a/drivers/net/ethernet/cadence/macb.h
> > +++ b/drivers/net/ethernet/cadence/macb.h
> > @@ -1309,6 +1309,8 @@ struct macb {
> >
> >       u32     rx_intr_mask;
> >
> > +     unsigned int is_opened;
> > +
> >       struct macb_pm_data pm_data;
> >       const struct macb_usrio_config *usrio;
> >  };
> > diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> > index 6bc7d41d519b..e079ed10ad91 100644
> > --- a/drivers/net/ethernet/cadence/macb_main.c
> > +++ b/drivers/net/ethernet/cadence/macb_main.c
> > @@ -2781,6 +2781,8 @@ static int macb_open(struct net_device *dev)
> >       if (bp->ptp_info)
> >               bp->ptp_info->ptp_init(dev);
> >
> > +     bp->is_opened = 1;
> > +
> >       return 0;
> >
> >  reset_hw:
> > @@ -2818,6 +2820,8 @@ static int macb_close(struct net_device *dev)
> >       if (bp->ptp_info)
> >               bp->ptp_info->ptp_remove(dev);
> >
> > +     bp->is_opened = 0;
> > +
> >       pm_runtime_put(&bp->pdev->dev);
> >
> >       return 0;
> > @@ -2867,6 +2871,9 @@ static struct net_device_stats *gem_get_stats(struct macb *bp)
> >       struct gem_stats *hwstat = &bp->hw_stats.gem;
> >       struct net_device_stats *nstat = &bp->dev->stats;
> >
> > +     if (!bp->is_opened)
> > +             return nstat;
>
> The canonical way to do this check is to use netif_running(), and not
> open code a boolean tracking whether a network device is opened or not.

Yes, I have tried this and it worked. Let me change it in the next version.

> --
> Florian