linux-kernel - Re: [PATCH net v2] r8169: fix rtl8125b PAUSE frames blasting when suspended

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Message-ID: <CANEJEGs9r0vq9QkGTcLryPnviMPgztJDsFjHqnRH65KbCqeF7g@mail.gmail.com>
Date:   Wed, 29 Nov 2023 15:40:50 -0800
From:   Grant Grundler <grundler@...omium.org>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     ChunHao Lin <hau@...ltek.com>, hkallweit1@...il.com,
        nic_swsd@...ltek.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, grundler@...omium.org,
        stable@...r.kernel.org
Subject: Re: [PATCH net v2] r8169: fix rtl8125b PAUSE frames blasting when suspended

On Wed, Nov 29, 2023 at 3:05 PM Jacob Keller <jacob.e.keller@...el.com> wrote:
> On 11/29/2023 7:53 AM, ChunHao Lin wrote:
> > When FIFO reaches near full state, device will issue pause frame.
> > If pause slot is enabled(set to 1), in this time, device will issue
> > pause frame only once. But if pause slot is disabled(set to 0), device
> > will keep sending pause frames until FIFO reaches near empty state.
> >
> > When pause slot is disabled, if there is no one to handle receive
> > packets, device FIFO will reach near full state and keep sending
> > pause frames. That will impact entire local area network.
> >
> > This issue can be reproduced in Chromebox (not Chromebook) in
> > developer mode running a test image (and v5.10 kernel):
> > 1) ping -f $CHROMEBOX (from workstation on same local network)
> > 2) run "powerd_dbus_suspend" from command line on the $CHROMEBOX
> > 3) ping $ROUTER (wait until ping fails from workstation)
> >
> > Takes about ~20-30 seconds after step 2 for the local network to
> > stop working.
> >
> > Fix this issue by enabling pause slot to only send pause frame once
> > when FIFO reaches near full state.
> >
>
> Makes sense. Avoiding the spam is good.  The naming is a bit confusing
> but I guess that comes from realtek datasheet?

I don't know. It doesn't matter to me what it's called since I don't
have access to the data sheet anyway. :/

> > Fixes: f1bce4ad2f1c ("r8169: add support for RTL8125")
> > Reported-by: Grant Grundler <grundler@...omium.org>
> > Tested-by: Grant Grundler <grundler@...omium.org>
> > Cc: stable@...r.kernel.org
> > Signed-off-by: ChunHao Lin <hau@...ltek.com>
> > ---
> > v2:
> > - update comment and title.
> > ---
> >  drivers/net/ethernet/realtek/r8169_main.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/realtek/r8169_main.c b/drivers/net/ethernet/realtek/r8169_main.c
> > index 62cabeeb842a..bb787a52bc75 100644
> > --- a/drivers/net/ethernet/realtek/r8169_main.c
> > +++ b/drivers/net/ethernet/realtek/r8169_main.c
> > @@ -196,6 +196,7 @@ enum rtl_registers {
> >                                       /* No threshold before first PCI xfer */
> >  #define      RX_FIFO_THRESH                  (7 << RXCFG_FIFO_SHIFT)
> >  #define      RX_EARLY_OFF                    (1 << 11)
> > +#define      RX_PAUSE_SLOT_ON                (1 << 11)       /* 8125b and later */
>
> This confuses me though: RX_EARLY_OFF is (1 << 11) as well.. Is that
> from a different set of devices?

Yes, for a different HW version of the device.

> We're writing to the same register
> RxConfig here I think in both cases?

Yes. But to different versions of the HW which use this bit
differently. Ergo the comment about "8125b and later".

> Can you clarify if these are supposed to be the same bit?

Yes, they are the same bit - but different versions of HW use BIT(11)
differently.

>
> >  #define      RXCFG_DMA_SHIFT                 8
> >                                       /* Unlimited maximum PCI burst. */
> >  #define      RX_DMA_BURST                    (7 << RXCFG_DMA_SHIFT)
> > @@ -2306,9 +2307,13 @@ static void rtl_init_rxcfg(struct rtl8169_private *tp)
> >       case RTL_GIGA_MAC_VER_40 ... RTL_GIGA_MAC_VER_53:
> >               RTL_W32(tp, RxConfig, RX128_INT_EN | RX_MULTI_EN | RX_DMA_BURST | RX_EARLY_OFF);
> >               break;
> > -     case RTL_GIGA_MAC_VER_61 ... RTL_GIGA_MAC_VER_63:
> > +     case RTL_GIGA_MAC_VER_61:
> >               RTL_W32(tp, RxConfig, RX_FETCH_DFLT_8125 | RX_DMA_BURST);
> >               break;
>
> I assume there isn't a VER_62 between these?

Correct. My clue is this code near the top of this file:

 149         [RTL_GIGA_MAC_VER_61] = {"RTL8125A",            FIRMWARE_8125A_3},
 150         /* reserve 62 for CFG_METHOD_4 in the vendor driver */
 151         [RTL_GIGA_MAC_VER_63] = {"RTL8125B",            FIRMWARE_8125B_2},

>
> > +     case RTL_GIGA_MAC_VER_63:
> > +             RTL_W32(tp, RxConfig, RX_FETCH_DFLT_8125 | RX_DMA_BURST |
> > +                     RX_PAUSE_SLOT_ON);
>
> We add RX_PAUSE_SLOT_ON now for RTL_GIGA_MAC_VER_63 in addition. Makes
> sense.

Exactly.

thanks for reviewing!

cheers,
grant

> > +             break;
> >       default:
> >               RTL_W32(tp, RxConfig, RX128_INT_EN | RX_DMA_BURST);
> >               break;