linux-kernel - Re: [PATCH 2/3] net: dsa: qca8k: change only max_frame_size of mac_frame_size

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Date:   Tue, 21 Jun 2022 15:30:41 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Christian Marangi <ansuelsmth@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jonathan McDowell <noodles@...th.li>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] net: dsa: qca8k: change only max_frame_size of
 mac_frame_size_reg

On Sat, Jun 18, 2022 at 08:22:59AM +0200, Christian Marangi wrote:
> Currently we overwrite the entire MAX_FRAME_SIZE reg instead of tweaking
> just the MAX_FRAME_SIZE value. Change this and update only the relevant
> bits.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@...il.com>
> ---
>  drivers/net/dsa/qca8k.c | 8 ++++++--
>  drivers/net/dsa/qca8k.h | 3 ++-
>  2 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index 2727d3169c25..eaaf80f96fa9 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -2345,7 +2345,9 @@ qca8k_port_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
>  		return 0;
>  
>  	/* Include L2 header / FCS length */
> -	return qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, new_mtu + ETH_HLEN + ETH_FCS_LEN);
> +	return regmap_update_bits(priv->regmap, QCA8K_MAX_FRAME_SIZE_REG,
> +				  QCA8K_MAX_FRAME_SIZE_MASK,
> +				  new_mtu + ETH_HLEN + ETH_FCS_LEN);
>  }
>  
>  static int
> @@ -3015,7 +3017,9 @@ qca8k_setup(struct dsa_switch *ds)
>  	}
>  
>  	/* Setup our port MTUs to match power on defaults */
> -	ret = qca8k_write(priv, QCA8K_MAX_FRAME_SIZE, ETH_FRAME_LEN + ETH_FCS_LEN);
> +	ret = regmap_update_bits(priv->regmap, QCA8K_MAX_FRAME_SIZE_REG,
> +				 QCA8K_MAX_FRAME_SIZE_MASK,
> +				 ETH_FRAME_LEN + ETH_FCS_LEN);
>  	if (ret)
>  		dev_warn(priv->dev, "failed setting MTU settings");
>  
> diff --git a/drivers/net/dsa/qca8k.h b/drivers/net/dsa/qca8k.h
> index ec58d0e80a70..1d0c383a95e7 100644
> --- a/drivers/net/dsa/qca8k.h
> +++ b/drivers/net/dsa/qca8k.h
> @@ -87,7 +87,8 @@
>  #define   QCA8K_MDIO_MASTER_MAX_REG			32
>  #define QCA8K_GOL_MAC_ADDR0				0x60
>  #define QCA8K_GOL_MAC_ADDR1				0x64
> -#define QCA8K_MAX_FRAME_SIZE				0x78
> +#define QCA8K_MAX_FRAME_SIZE_REG			0x78
> +#define   QCA8K_MAX_FRAME_SIZE_MASK			GENMASK(13, 0)

What's at bits 14 and beyond? Trying to understand the impact of this change.

>  #define QCA8K_REG_PORT_STATUS(_i)			(0x07c + (_i) * 4)
>  #define   QCA8K_PORT_STATUS_SPEED			GENMASK(1, 0)
>  #define   QCA8K_PORT_STATUS_SPEED_10			0
> -- 
> 2.36.1
>