netdev - Re: [PATCH net-next 0/5] Flow control for NXP ENETC

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Message-ID: <20210420140433.hajuvfiz4humhhkt@skbuf>
Date:   Tue, 20 Apr 2021 17:04:33 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Michael Walle <michael@...le.cc>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Po Liu <po.liu@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alex Marginean <alexandru.marginean@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Vladimir Oltean <vladimir.oltean@....com>
Subject: Re: [PATCH net-next 0/5] Flow control for NXP ENETC

Hi Michael,

On Tue, Apr 20, 2021 at 03:27:24PM +0200, Michael Walle wrote:
> Hi Vladimir,
> 
> Am 2021-04-17 01:42, schrieb Vladimir Oltean:
> > From: Vladimir Oltean <vladimir.oltean@....com>
> > 
> > This patch series contains logic for enabling the lossless mode on the
> > RX rings of the ENETC, and the PAUSE thresholds on the internal FIFO
> > memory.
> > 
> > During testing it was found that, with the default FIFO configuration,
> > a sender which isn't persuaded by our PAUSE frames and keeps sending
> > will cause some MAC RX frame errors. To mitigate this, we need to ensure
> > that the FIFO never runs completely full, so we need to fix up a setting
> > that was supposed to be configured well out of reset. Unfortunately this
> > requires the addition of a new mini-driver.
> 
> What happens if the mini driver is not enabled? Then the fixes aren't
> applied and bad things happen (now with the addition of flow control),
> right?
> 
> I'm asking because, if you have the arm64 defconfig its not enabled.
> 
> shouldn't it be something like:
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/Kconfig
> b/drivers/net/ethernet/freescale/enetc/Kconfig
> index d88f60c2bb82..cdc0ff89388a 100644
> --- a/drivers/net/ethernet/freescale/enetc/Kconfig
> +++ b/drivers/net/ethernet/freescale/enetc/Kconfig
> @@ -2,7 +2,7 @@
>  config FSL_ENETC
>         tristate "ENETC PF driver"
>         depends on PCI && PCI_MSI
> -       depends on FSL_ENETC_IERB || FSL_ENETC_IERB=n
> +       select FSL_ENETC_IERB
>         select FSL_ENETC_MDIO
>         select PHYLINK
>         select PCS_LYNX

Yes, ideally the IERB driver and the ENETC PF driver should be built in
the same way, or the IERB driver can be built-in and the PF driver can
be module. I don't know how to express this using Kconfig, sorry.