Re: [PATCH net-next v4 2/8] dt-bindings: net: fman: Add additional interface properties

From: Rob Herring <robh@kernel.org>
To: Sean Anderson <sean.anderson@seco.com>
Cc: Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	netdev@vger.kernel.org, "David S . Miller" <davem@davemloft.net>,
	devicetree@vger.kernel.org,
	"linuxppc-dev @ lists . ozlabs . org"
	<linuxppc-dev@lists.ozlabs.org>,
	Russell King <linux@armlinux.org.uk>,
	linux-kernel@vger.kernel.org,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Eric Dumazet <edumazet@google.com>,
	Madalin Bucur <madalin.bucur@nxp.com>,
	linux-arm-kernel@lists.infradead.org,
	Camelia Alexandra Groza <camelia.groza@nxp.com>,
	Rob Herring <robh+dt@kernel.org>
Subject: Re: [PATCH net-next v4 2/8] dt-bindings: net: fman: Add additional interface properties
Date: Mon, 22 Aug 2022 12:45:59 -0500	[thread overview]
Message-ID: <20220822174559.GA39398-robh@kernel.org> (raw)
In-Reply-To: <20220804194705.459670-3-sean.anderson@seco.com>

On Thu, 04 Aug 2022 15:46:59 -0400, Sean Anderson wrote:
> At the moment, mEMACs are configured almost completely based on the
> phy-connection-type. That is, if the phy interface is RGMII, it assumed
> that RGMII is supported. For some interfaces, it is assumed that the
> RCW/bootloader has set up the SerDes properly. This is generally OK, but
> restricts runtime reconfiguration. The actual link state is never
> reported.
> 
> To address these shortcomings, the driver will need additional
> information. First, it needs to know how to access the PCS/PMAs (in
> order to configure them and get the link status). The SGMII PCS/PMA is
> the only currently-described PCS/PMA. Add the XFI and QSGMII PCS/PMAs as
> well. The XFI (and 10GBASE-KR) PCS/PMA is a c45 "phy" which sits on the
> same MDIO bus as SGMII PCS/PMA. By default they will have conflicting
> addresses, but they are also not enabled at the same time by default.
> Therefore, we can let the XFI PCS/PMA be the default when
> phy-connection-type is xgmii. This will allow for
> backwards-compatibility.
> 
> QSGMII, however, cannot work with the current binding. This is because
> the QSGMII PCS/PMAs are only present on one MAC's MDIO bus. At the
> moment this is worked around by having every MAC write to the PCS/PMA
> addresses (without checking if they are present). This only works if
> each MAC has the same configuration, and only if we don't need to know
> the status. Because the QSGMII PCS/PMA will typically be located on a
> different MDIO bus than the MAC's SGMII PCS/PMA, there is no fallback
> for the QSGMII PCS/PMA.
> 
> Signed-off-by: Sean Anderson <sean.anderson@seco.com>
> ---
> 
> (no changes since v3)
> 
> Changes in v3:
> - Add vendor prefix 'fsl,' to rgmii and mii properties.
> - Set maxItems for pcs-names
> - Remove phy-* properties from example because dt-schema complains and I
>   can't be bothered to figure out how to make it work.
> - Add pcs-handle as a preferred version of pcsphy-handle
> - Deprecate pcsphy-handle
> - Remove mii/rmii properties
> 
> Changes in v2:
> - Better document how we select which PCS to use in the default case
> 
>  .../bindings/net/fsl,fman-dtsec.yaml          | 53 ++++++++++++++-----
>  .../devicetree/bindings/net/fsl-fman.txt      |  5 +-
>  2 files changed, 43 insertions(+), 15 deletions(-)
> 

Reviewed-by: Rob Herring <robh@kernel.org>