linux-kernel - Re: [PATCH v2 4/7] net: phy: add helper for mapping RGMII link speed to clock rate

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Message-ID: <20240819141541.GE11472@kernel.org>
Date: Mon, 19 Aug 2024 15:15:41 +0100
From: Simon Horman <horms@...nel.org>
To: "Jan Petrous (OSS)" <jan.petrous@....nxp.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Vinod Koul <vkoul@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Richard Cochran <richardcochran@...il.com>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-stm32@...md-mailman.stormreply.com" <linux-stm32@...md-mailman.stormreply.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	dl-S32 <S32@....com>
Subject: Re: [PATCH v2 4/7] net: phy: add helper for mapping RGMII link speed
 to clock rate

On Sun, Aug 18, 2024 at 09:50:46PM +0000, Jan Petrous (OSS) wrote:
> The helper rgmii_clock() implemented Russel's hint during stmmac
> glue driver review:
> 
> ---
> We seem to have multiple cases of very similar logic in lots of stmmac
> platform drivers, and I think it's about time we said no more to this.
> So, what I think we should do is as follows:
> 
> add the following helper - either in stmmac, or more generically
> (phylib? - in which case its name will need changing.)
> 
> static long stmmac_get_rgmii_clock(int speed)
> {
> 	switch (speed) {
> 	case SPEED_10:
> 		return 2500000;
> 
> 	case SPEED_100:
> 		return 25000000;
> 
> 	case SPEED_1000:
> 		return 125000000;
> 
> 	default:
> 		return -ENVAL;
> 	}
> }
> 
> Then, this can become:
> 
> 	long tx_clk_rate;
> 
> 	...
> 
> 	tx_clk_rate = stmmac_get_rgmii_clock(speed);
> 	if (tx_clk_rate < 0) {
> 		dev_err(gmac->dev, "Unsupported/Invalid speed: %d\n", speed);
> 		return;
> 	}
> 
> 	ret = clk_set_rate(gmac->tx_clk, tx_clk_rate);
> ---
> 
> Signed-off-by: Jan Petrous (OSS) <jan.petrous@....nxp.com>
> ---
>  include/linux/phy.h | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 6b7d40d49129..bb797364d91c 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -298,6 +298,27 @@ static inline const char *phy_modes(phy_interface_t interface)
>  	}
>  }
>  
> +/**
> + * rgmi_clock - map link speed to the clock rate

nit: rgmii_clock

     Flagged by ./scripts/kernel-doc -none

> + * @speed: link speed value
> + *
> + * Description: maps RGMII supported link speeds
> + * into the clock rates.
> + */
> +static inline long rgmii_clock(int speed)
> +{
> +	switch (speed) {
> +	case SPEED_10:
> +		return 2500000;
> +	case SPEED_100:
> +		return 25000000;
> +	case SPEED_1000:
> +		return 125000000;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
>  #define PHY_INIT_TIMEOUT	100000
>  #define PHY_FORCE_TIMEOUT	10
>  
> -- 
> 2.46.0
> 
>