linux-kernel - Re: [PATCH net] net: phy: realtek: Reset after clock enable

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Message-ID: <e1df8097-dd48-4570-8f8e-c6c25a3683a4@lunn.ch>
Date: Sat, 5 Jul 2025 10:10:40 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Sebastian Reichel <sebastian.reichel@...labora.com>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Detlev Casanova <detlev.casanova@...labora.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH net] net: phy: realtek: Reset after clock enable

On Fri, Jul 04, 2025 at 07:48:44PM +0200, Sebastian Reichel wrote:
> On Radxa ROCK 4D boards we are seeing some issues with PHY detection and
> stability (e.g. link loss, or not capable of transceiving packages)
> after new board revisions switched from a dedicated crystal to providing
> the 25 MHz PHY input clock from the SoC instead.
> 
> This board is using a RTL8211F PHY, which is connected to an always-on
> regulator. Unfortunately the datasheet does not explicitly mention the
> power-up sequence regarding the clock, but it seems to assume that the
> clock is always-on (i.e. dedicated crystal).
> 
> By doing an explicit reset after enabling the clock, the issue on the
> boards could no longer be observed.

I don't know if it helps in this situation, but look at
PHY_RST_AFTER_CLK_EN.

If it does not actually help, it might be worth mentioning it in the
commit message to stop reviewers saying you should see if it is
useful.

	Andrew