netdev - Re: [PATCH net-next 01/11] net: stmmac: provide set_clk_tx

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Message-ID: <97073a6f-3200-46da-856b-e7431e09c859@lunn.ch>
Date: Thu, 27 Feb 2025 14:57:51 +0100
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com,
	Maxime Coquelin <mcoquelin.stm32@...il.com>, netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next 01/11] net: stmmac: provide set_clk_tx_rate()
 hook

On Thu, Feb 27, 2025 at 09:16:23AM +0000, Russell King (Oracle) wrote:
> Several stmmac sub-drivers which support RGMII follow the same pattern.
> They calculate the transmit clock rate, and then call clk_set_rate().
> 
> Analysis of several implementation documents suggests that the platform
> is responsible for providing the transmit clock to the DWMAC core's
> clk_tx_i. The expected rates are:
> 
> 	10Mbps	100Mbps	1Gbps
> MII	2.5MHz	25MHz
> RMII	2.5MHz	25MHz
> GMII			125MHz
> RGMI	2.5MHz	25MHz	125MHz
> 
> It seems some platforms require this clock to be manually configured,
> but there are outputs from the MAC core that indicate the speed, so a
> platform may use these to automatically configure the clock. Thus, we
> can't just provide one solution to configure this clock rate.
> 
> Moreover, the clock may need to be derived from one of several sources
> depending on the interface mode.
> 
> Provide a platform hook that is passed the transmit clock, interface
> mode and speed.
> 
> Reviewed-by: Thierry Reding <treding@...dia.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

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

    Andrew