netdev - Re: [PATCH CFT net-next 0/6] net: stmmac/xpcs: modernise PCS support

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Message-ID: <20211217055729.GA14835@linux.intel.com>
Date:   Fri, 17 Dec 2021 13:57:29 +0800
From:   Wong Vee Khee <vee.khee.wong@...ux.intel.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jose Abreu <joabreu@...opsys.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com, netdev@...r.kernel.org
Subject: Re: [PATCH CFT net-next 0/6] net: stmmac/xpcs: modernise PCS support

On Thu, Dec 16, 2021 at 01:11:40PM +0000, Russell King (Oracle) wrote:
> Hi,
> 
> This series updates xpcs and stmmac for the recent changes to phylink
> to better support split PCS and to get rid of private MAC validation
> functions.
> 
> This series is slightly more involved than other conversions as stmmac
> has already had optional proper split PCS support.
> 
> The patches:
> 
> 1) Provide a function to query the xpcs for the interface modes that
>    are supported.
> 
> 2) Populates the MAC capabilities and switches stmmac_validate() to use
>    phylink_get_linkmodes(). We do not use phylink_generic_validate() yet
>    as (a) we do not always have the supported interfaces populated, and
>    (b) the existing code does not restrict based on interface. There
>    should be no functional effect from this patch.
> 
> 3) Populates phylink's supported interfaces from the xpcs when the xpcs
>    is configured by firmware and also the firmware configured interface
>    mode. Note: this will restrict stmmac to only supporting these
>    interfaces modes - stmmac maintainers need to verify that this
>    behaviour is acceptable.
> 
> 4) stmmac_validate() tail-calls xpcs_validate(), but we don't need it to
>    now that PCS have their own validation method. Convert stmmac and
>    xpcs to use this method instead.
> 
> 5) xpcs sets the poll field of phylink_pcs to true, meaning xpcs
>    requires its status to be polled. There is no need to also set the
>    phylink_config.pcs_poll. Remove this.
> 
> 6) Switch to phylink_generic_validate(). This is probably the most
>    contravertial change in this patch set as this will cause the MAC to
>    restrict link modes based on the interface mode. From an inspection
>    of the xpcs driver, this should be safe, as XPCS only further
>    restricts the link modes to a subset of these (whether that is
>    correct or not is not an issue I am addressing here.) For
>    implementations that do not use xpcs, this is a more open question
>    and needs feedback from stmmac maintainers.
> 
> Please review and test this series. Thanks!
> 

Tested this patch series on my Intel Elkhart Lake setup with Marvell
88E1510 PHY. 

Everything works perfectly!

>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 144 ++++++----------------
>  drivers/net/pcs/pcs-xpcs.c                        |  41 +++---
>  include/linux/pcs/pcs-xpcs.h                      |   3 +-
>  3 files changed, 67 insertions(+), 121 deletions(-)