netdev - Re: [PATCH v2 5/6] net: phy: DP83640: Explicitly disabling PHY Control Frames

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Message-ID: <20240227110802.552bff55@device-28.home>
Date: Tue, 27 Feb 2024 11:08:02 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Bastien Curutchet <bastien.curutchet@...tlin.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+dt@...nel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>,
 Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>, Richard Cochran
 <richardcochran@...il.com>, Andrew Lunn <andrew@...n.ch>, Heiner Kallweit
 <hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>,
 linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 devicetree@...r.kernel.org, linux-leds@...r.kernel.org, Thomas Petazzoni
 <thomas.petazzoni@...tlin.com>, herve.codina@...tlin.com,
 christophercordahi@...ometrics.ca
Subject: Re: [PATCH v2 5/6] net: phy: DP83640: Explicitly disabling PHY
 Control Frames

Hi Bastien,

On Tue, 27 Feb 2024 10:39:44 +0100
Bastien Curutchet <bastien.curutchet@...tlin.com> wrote:

> The PHY offers a PHY control frame feature that allows to access PHY
> registers through the MAC transmit data interface. This functionality
> is not handled by the driver but can be enabled via hardware strap or
> register access.
> 
> Disable the feature in config_init() to save some latency on MII packets.
> 
> Signed-off-by: Bastien Curutchet <bastien.curutchet@...tlin.com>
> ---
>  drivers/net/phy/dp83640.c     | 6 ++++++
>  drivers/net/phy/dp83640_reg.h | 4 ++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/drivers/net/phy/dp83640.c b/drivers/net/phy/dp83640.c
> index 16c9fda50b19..b371dea23937 100644
> --- a/drivers/net/phy/dp83640.c
> +++ b/drivers/net/phy/dp83640.c
> @@ -1120,6 +1120,7 @@ static int dp83640_config_init(struct phy_device *phydev)
>  {
>  	struct dp83640_private *dp83640 = phydev->priv;
>  	struct dp83640_clock *clock = dp83640->clock;
> +	int val;
>  
>  	if (clock->chosen && !list_empty(&clock->phylist))
>  		recalibrate(clock);
> @@ -1135,6 +1136,11 @@ static int dp83640_config_init(struct phy_device *phydev)
>  	ext_write(0, phydev, PAGE4, PTP_CTL, PTP_ENABLE);
>  	mutex_unlock(&clock->extreg_lock);
>  
> +	/* Disable unused PHY control frames */
> +	phy_write(phydev, PAGESEL, 0);
> +	val = phy_read(phydev, PCFCR) & ~PCF_EN;
> +	phy_write(phydev, PCFCR, val);

Use phy_modify instead, and you might also want to look at the paging.
The ext_write before apparently does some page-management itself through
the clock struct (?).

> +
>  	return 0;
>  }
>  
> diff --git a/drivers/net/phy/dp83640_reg.h b/drivers/net/phy/dp83640_reg.h
> index bf34d422d91e..b5adb8958c08 100644
> --- a/drivers/net/phy/dp83640_reg.h
> +++ b/drivers/net/phy/dp83640_reg.h
> @@ -10,6 +10,7 @@
>  #define PHYCR                     0x0019 /* PHY Control Register */
>  #define PHYCR2                    0x001c /* PHY Control Register 2 */
>  #define EDCR                      0x001D /* Energy Detect Control Register */
> +#define PCFCR                     0x001F /* PHY Control Frames Control Register */
>  
>  #define PAGE4                     0x0004
>  #define PTP_CTL                   0x0014 /* PTP Control Register */
> @@ -68,6 +69,9 @@
>  /* Bit definitions for the EDCR register */
>  #define ED_EN		          BIT(15) /* Enable Energy Detect Mode */
>  
> +/* Bit definitions for the PCFCR register */
> +#define PCF_EN                    BIT(0)  /* Enable PHY Control Frames */
> +
>  /* Bit definitions for the PTP_CTL register */
>  #define TRIG_SEL_SHIFT            (10)    /* PTP Trigger Select */
>  #define TRIG_SEL_MASK             (0x7)

Thanks,

Maxime