linux-kernel - Re: [net-next RFC PATCH 12/14] dt-bindings: net: Document Qcom QCA807x PHY package

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Date:   Thu, 23 Nov 2023 12:20:24 +0100
From:   Robert Marko <robert.marko@...tura.hr>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Christian Marangi <ansuelsmth@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Daniel Golle <daniel@...rotopia.org>,
        Qingfang Deng <dqfext@...il.com>,
        SkyLake Huang <SkyLake.Huang@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        David Epping <david.epping@...singlinkelectronics.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Harini Katakam <harini.katakam@....com>,
        Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [net-next RFC PATCH 12/14] dt-bindings: net: Document Qcom
 QCA807x PHY package

On Thu, Nov 23, 2023 at 3:15 AM Andrew Lunn <andrew@...n.ch> wrote:
>
> > +  They feature 2 SerDes, one for PSGMII or QSGMII connection with
> > +  MAC, while second one is SGMII for connection to MAC or fiber.
>
> Can you connect 1/5 of the PSGMII SERDES to the SGMII SERDES? So
> making use of the PHY as a media converter to connect to an SFP cage?
> I assume the SGMII serdes can also do 1000BaseX?
>
> How do you describe what the SGMII SERDES is connected to?

Hi Andrew,
I think that the description is confusing.
QCA807x supports 3 different modes:
1. PSGMII (5 copper ports)
2. PSGMII (4 copper ports + 1 combo port)
3. QSGMII+SGMII

So, in case option 2 is selected then the combo port can also be used for
1000Base-X and 100Base-FX modules or copper and it will autodetect the
exact media.
This is supported via the SFP op-s and I have been using it without issues
for a while.

I have not tested option 3 in combination with SFP to the copper
module so I cant
say whether that works.
>From what I can gather from the typical usage examples in the
datasheet, this QSMII+SGMII
mode is basically intended as a backward compatibility thing as only
QCA SoC-s have PSGMII
support so that you could still use SoC-s with QSGMII and SGMII support only.

So there is no way to control the SerDes-es individually, only the
global mode can be changed via
the Chip configuration register in the Combo port.

You can see the block diagram of this PHY in this public PDF on page 2[1].

[1] https://content.codico.com/fileadmin/media/download/datasheets/qualcomm/qualcomm_qca8075.pdf

>
>   Andrew
>


-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura Ltd.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@...tura.hr
Web: www.sartura.hr