linux-kernel - RE: [RFC,net-next,v1, 1/1] net: stmmac: Enable SERDES power up/down sequence

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Message-ID: <BN8PR12MB3266ACFFA4808A133BB72F9DD3F00@BN8PR12MB3266.namprd12.prod.outlook.com>
Date:   Mon, 23 Mar 2020 07:46:39 +0000
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     Voon Weifeng <weifeng.voon@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Giuseppe Cavallaro" <peppe.cavallaro@...com>,
        Andrew Lunn <andrew@...n.ch>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Ong Boon Leong <boon.leong.ong@...el.com>
Subject: RE: [RFC,net-next,v1, 1/1] net: stmmac: Enable SERDES power up/down
 sequence

From: Voon Weifeng <weifeng.voon@...el.com>
Date: Mar/22/2020, 13:23:42 (UTC+00:00)

> This patch is to enable Intel SERDES power up/down sequence. The SERDES
> converts 8/10 bits data to SGMII signal. Below is an example of
> HW configuration for SGMII mode. The SERDES is located in the PHY IF
> in the diagram below.
> 
> <-----------------GBE Controller---------->|<--External PHY chip-->
> +----------+         +----+            +---+           +----------+
> |   EQoS   | <-GMII->| DW | < ------ > |PHY| <-SGMII-> | External |
> |   MAC    |         |xPCS|            |IF |           | PHY      |
> +----------+         +----+            +---+           +----------+
>        ^               ^                 ^                ^
>        |               |                 |                |
>        +---------------------MDIO-------------------------+
> 
> PHY IF configuration and status registers are accessible through
> mdio address 0x15 which is defined as intel_adhoc_addr. During D0,
> The driver will need to power up PHY IF by changing the power state
> to P0. Likewise, for D3, the driver sets PHY IF power state to P3.

I don't think this is the right approach.

You could just add a new "mdio-intel-serdes" to phy/ folder just like I 
did with XPCS because this is mostly related with PHY settings rather than 
EQoS.

Perhaps Andrew has better insight on this.

BTW, are you using the standard XPCS helpers in phy/ folder ? Is it 
working fine for you ?

---
Thanks,
Jose Miguel Abreu