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

[Andrew Lunn <andrew@lunn.ch>]

> On Thu, Jul 24, 2025 at 05:17:49PM -0700, Tristram.Ha@microchip.com wrote:
> From: Tristram Ha <tristram.ha@microchip.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@microchip.com>

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

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

    Andrew