linux-kernel - Re: [PATCH net-next v6 2/6] net: dsa: microchip: Add KSZ8463 switch support to KSZ DSA driver

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Message-ID: <6fc3ef55-68f7-4b1a-aa8f-70dc8ffdba3e@lunn.ch>
Date: Fri, 25 Jul 2025 14:27:39 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Tristram.Ha@...rochip.com
Cc: Woojung Huh <woojung.huh@...rochip.com>,
	Vladimir Oltean <olteanv@...il.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Simon Horman <horms@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Marek Vasut <marex@...x.de>, UNGLinuxDriver@...rochip.com,
	devicetree@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v6 2/6] net: dsa: microchip: Add KSZ8463 switch
 support to KSZ DSA driver

> On Thu, Jul 24, 2025 at 05:17:49PM -0700, Tristram.Ha@...rochip.com wrote:
> From: Tristram Ha <tristram.ha@...rochip.com>
> 
> KSZ8463 switch is a 3-port switch based from KSZ8863.  Its major
> difference from other KSZ SPI switches is its register access is not a
> simple continual 8-bit transfer with automatic address increase but uses
> a byte-enable mechanism specifying 8-bit, 16-bit, or 32-bit access.  Its
> registers are also defined in 16-bit format because it shares a design
> with a MAC controller using 16-bit access.  As a result some common
> register accesses need to be re-arranged.
> 
> This patch adds the basic structure for using KSZ8463.  It cannot use the
> same regmap table for other KSZ switches as it interprets the 16-bit
> value as little-endian and its SPI commands are different.
> 
> KSZ8463 uses a byte-enable mechanism to specify 8-bit, 16-bit, and 32-bit
> access.  The register is first shifted right by 2 then left by 4.  Extra
> 4 bits are added.  If the access is 8-bit one of the 4 bits is set.  If
> the access is 16-bit two of the 4 bits are set.  If the access is 32-bit
> all 4 bits are set.  The SPI command for read or write is then added.
> 
> Because of this register transformation separate SPI read and write
> functions are provided for KSZ8463.
> 
> KSZ8463's internal PHYs use standard PHY register definitions so there is
> no need to remap things.  However, the hardware has a bug that the high
> word and low word of the PHY id are swapped.  In addition the port
> registers are arranged differently so KSZ8463 has its own mapping for
> port registers and PHY registers.  Therefore the PORT_CTRL_ADDR macro is
> replaced with the get_port_addr helper function.
> 
> Signed-off-by: Tristram Ha <tristram.ha@...rochip.com>

Thanks for keeping working on regmap. The end result is a lot better,
smaller.

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew