netdev - Re: [PATCH v8 RESEND 6/6] r8169: Disable ASPM while doing NAPI poll

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Message-ID: <CAAd53p79Of-ZPBFGtBZCSnST+oTT5AwGkRo_Z57Gm9XDOBmi_A@mail.gmail.com>
Date:   Wed, 22 Feb 2023 21:03:01 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     nic_swsd@...ltek.com, bhelgaas@...gle.com, koba.ko@...onical.com,
        acelan.kao@...onical.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com, vidyas@...dia.com,
        rafael.j.wysocki@...el.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH v8 RESEND 6/6] r8169: Disable ASPM while doing NAPI poll

On Tue, Feb 21, 2023 at 7:09 PM Heiner Kallweit <hkallweit1@...il.com> wrote:
>
> On 21.02.2023 03:38, Kai-Heng Feng wrote:
> > NAPI poll of Realtek NICs don't seem to perform well ASPM is enabled.
> > The vendor driver uses a mechanism called "dynamic ASPM" to toggle ASPM
> > based on the packet number in given time period.
> >
> > Instead of implementing "dynamic ASPM", use a more straightforward way
> > by disabling ASPM during NAPI poll, as a similar approach was
> > implemented to solve slow performance on Realtek wireless NIC, see
> > commit 24f5e38a13b5 ("rtw88: Disable PCIe ASPM while doing NAPI poll on
> > 8821CE").
> >
> > Since NAPI poll should be handled as fast as possible, also remove the
> > delay in rtl_hw_aspm_clkreq_enable() which was added by commit
> > 94235460f9ea ("r8169: Align ASPM/CLKREQ setting function with vendor
> > driver").
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> > ---
> > v8:
> >  - New patch.
> >
> >  drivers/net/ethernet/realtek/r8169_main.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> > index 897f90b48bba6..4d4a802346ae3 100644
> > --- a/drivers/net/ethernet/realtek/r8169_main.c
> > +++ b/drivers/net/ethernet/realtek/r8169_main.c
> > @@ -2711,8 +2711,6 @@ static void rtl_hw_aspm_clkreq_enable(struct rtl8169_private *tp, bool enable)
> >               RTL_W8(tp, Config2, RTL_R8(tp, Config2) & ~ClkReqEn);
> >               RTL_W8(tp, Config5, RTL_R8(tp, Config5) & ~ASPM_en);
> >       }
> > -
> > -     udelay(10);
> >  }
> >
> >  static void rtl_set_fifo_size(struct rtl8169_private *tp, u16 rx_stat,
> > @@ -4577,6 +4575,12 @@ static int rtl8169_poll(struct napi_struct *napi, int budget)
> >       struct net_device *dev = tp->dev;
> >       int work_done;
> >
> > +     if (tp->aspm_manageable) {
> > +             rtl_unlock_config_regs(tp);
>
> NAPI poll runs in softirq context (except for threaded NAPI).
> Therefore you should use a spinlock instead of a mutex.

You are right. Will change it in next revision.

>
> > +             rtl_hw_aspm_clkreq_enable(tp, false);
> > +             rtl_lock_config_regs(tp);
> > +     }
> > +
> >       rtl_tx(dev, tp, budget);
> >
> >       work_done = rtl_rx(dev, tp, budget);
> > @@ -4584,6 +4588,12 @@ static int rtl8169_poll(struct napi_struct *napi, int budget)
> >       if (work_done < budget && napi_complete_done(napi, work_done))
> >               rtl_irq_enable(tp);
> >
> > +     if (tp->aspm_manageable) {
> > +             rtl_unlock_config_regs(tp);
> > +             rtl_hw_aspm_clkreq_enable(tp, true);
> > +             rtl_lock_config_regs(tp);
>
> Why not moving lock/unlock into rtl_hw_aspm_clkreq_enable()?

Because where it gets called at other places don't need the lock.
But yes this will make it easier to read, will do in next revision.

Kai-Heng

>
> > +     }
> > +
> >       return work_done;
> >  }
> >
>