linux-kernel - Re: [PATCH] net: dsa: microchip: KSZ9477 register regmap alignment to 32 bit boundaries

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Message-ID: <ZMTxjP5dReD6+B3P@kernel.org>
Date:   Sat, 29 Jul 2023 13:01:32 +0200
From:   Simon Horman <horms@...nel.org>
To:     Lukasz Majewski <lukma@...x.de>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [PATCH] net: dsa: microchip: KSZ9477 register regmap alignment
 to 32 bit boundaries

On Thu, Jul 27, 2023 at 10:13:42AM +0200, Lukasz Majewski wrote:
> The commit (SHA1: 5c844d57aa7894154e49cf2fc648bfe2f1aefc1c) provided code
> to apply "Module 6: Certain PHY registers must be written as pairs instead
> of singly" errata for KSZ9477 as this chip for certain PHY registers
> (0xN120 to 0xN13F, N=1,2,3,4,5) must be accesses as 32 bit words instead
> of 16 or 8 bit access.
> Otherwise, adjacent registers (no matter if reserved or not) are
> overwritten with 0x0.
> 
> Without this patch some registers (e.g. 0x113c or 0x1134) required for 32
> bit access are out of valid regmap ranges.
> 
> As a result, following error is observed and KSZ9477 is not properly
> configured:
> 
> ksz-switch spi1.0: can't rmw 32bit reg 0x113c: -EIO
> ksz-switch spi1.0: can't rmw 32bit reg 0x1134: -EIO
> ksz-switch spi1.0 lan1 (uninitialized): failed to connect to PHY: -EIO
> ksz-switch spi1.0 lan1 (uninitialized): error -5 setting up PHY for tree 0, switch 0, port 0
> 
> 
> The solution is to modify regmap_reg_range to allow accesses with 4 bytes
> boundaries.
> 
> Signed-off-by: Lukasz Majewski <lukma@...x.de>

Reviewed-by: Simon Horman <horms@...nel.org>