linux-kernel - Re: [PATCH v4 3/5] mfd: Add RTL8231 core device

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Message-ID: <YLjhT1zL/6okGP3p@lunn.ch>
Date:   Thu, 3 Jun 2021 16:03:59 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Sander Vanheule <sander@...nheule.net>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Michael Walle <michael@...le.cc>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/5] mfd: Add RTL8231 core device

> I wanted to make the masking explicit, but since regmap-mdio currently requires
> a register address width of 5 bit, it could move there.
> 
> Actually, can we safely assume that any MDIO driver implementing clause-22
> access (5-bit register address width) will just ignore higher bits? In that
> case, I could just drop these functions and not even modify regmap-mdio. It
> appears to work for bitbanged MDIO.

How are C45 addresses handled? The API to the MDIO bus driver uses a
register value which is 32 bits in width. Bit 30 indicates the address
is a C45 address, and then you have 21 bits of actual address.
regmap-mdio needs to be generic and support both C22 and C45.

   Andrew