netdev - Re: [PATCH v2 2/2] net: ethernet: Add driver for Sunplus SP7021

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Date:   Fri, 26 Nov 2021 20:32:40 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Wells Lu 呂芳騰 <wells.lu@...plus.com>
Cc:     Wells Lu <wellslutw@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        Vincent Shih 施錕鴻 
        <vincent.shih@...plus.com>
Subject: Re: [PATCH v2 2/2] net: ethernet: Add driver for Sunplus SP7021

On Fri, Nov 26, 2021 at 07:13:23PM +0000, Wells Lu 呂芳騰 wrote:
> Hi Andrew,
> 
> I read specification of ICPlus IP101G (10M/100M PHY).
> Bits of register 0 (control) and register 1 (status) 
> are R/W or RO type. They will not be cleared after 
> read. No matter how many times they are read, the 
> read-back value is the same.

Please read 802.3,

Section 22.2.4.2: Status register (Register 1)

Table 22-8 Status register bit definitions

Bit 1.2 Link Status is marked as RO/LL, meaning read only Latching
low.

> Can we go with this approach?

You need to not make any read on the PHY which Linux is driving.
Configure the hardware to read on an address where there is no PHY.

	Andrew