linux-kernel - Re: [PATCH net v2 1/1] net: dsa: microchip: lan937x: Fix RGMII delay tuning

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Message-ID: <1d2b2c4c-9e52-4ffb-9774-ea98521e95d5@redhat.com>
Date: Tue, 18 Nov 2025 15:14:26 +0100
From: Paolo Abeni <pabeni@...hat.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>,
 "David S. Miller" <davem@...emloft.net>, Andrew Lunn <andrew@...n.ch>,
 Eric Dumazet <edumazet@...gle.com>, Florian Fainelli <f.fainelli@...il.com>,
 Jakub Kicinski <kuba@...nel.org>, Vladimir Oltean <olteanv@...il.com>,
 Woojung Huh <woojung.huh@...rochip.com>,
 Arun Ramadoss <arun.ramadoss@...rochip.com>
Cc: stable@...r.kernel.org, kernel@...gutronix.de,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net v2 1/1] net: dsa: microchip: lan937x: Fix RGMII delay
 tuning

On 11/14/25 10:09 AM, Oleksij Rempel wrote:
> Correct RGMII delay application logic in lan937x_set_tune_adj().
> 
> The function was missing `data16 &= ~PORT_TUNE_ADJ` before setting the
> new delay value. This caused the new value to be bitwise-OR'd with the
> existing PORT_TUNE_ADJ field instead of replacing it.
> 
> For example, when setting the RGMII 2 TX delay on port 4, the
> intended TUNE_ADJUST value of 0 (RGMII_2_TX_DELAY_2NS) was
> incorrectly OR'd with the default 0x1B (from register value 0xDA3),
> leaving the delay at the wrong setting.
> 
> This patch adds the missing mask to clear the field, ensuring the
> correct delay value is written. Physical measurements on the RGMII TX
> lines confirm the fix, showing the delay changing from ~1ns (before
> change) to ~2ns.
> 
> While testing on i.MX 8MP showed this was within the platform's timing
> tolerance, it did not match the intended hardware-characterized value.
> 
> Fixes: b19ac41faa3f ("net: dsa: microchip: apply rgmii tx and rx delay in phylink mac config")
> Cc: stable@...r.kernel.org
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>

Lacking the changelog and reference to the previous submission, it took
me a little to notice that the only difference is the added Cc: tag.

Please:
- ask explicitly before going ahead with such repost, as manual tag
propagation is sometimes preferable
- always include a suitable changelog and reference to prior revisions

Thanks,

Paolo