linux-kernel - Re: [PATCH net-next 12/30] net: dsa: mt7530: move XTAL check to mt7530

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Message-ID: <20230524181512.tmll4ijpijmc5fea@skbuf>
Date:   Wed, 24 May 2023 21:15:12 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     arinc9.unal@...il.com
Cc:     Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>,
        Daniel Golle <daniel@...rotopia.org>,
        Andrew Lunn <andrew@...n.ch>,
        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>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Russell King <linux@...linux.org.uk>,
        Arınç ÜNAL <arinc.unal@...nc9.com>,
        Richard van Schagen <richard@...terhints.com>,
        Richard van Schagen <vschagen@...com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Bartel Eerdekens <bartel.eerdekens@...stell8.be>,
        erkin.bozoglu@...ont.com, mithat.guner@...ont.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next 12/30] net: dsa: mt7530: move XTAL check to
 mt7530_setup()

On Mon, May 22, 2023 at 03:15:14PM +0300, arinc9.unal@...il.com wrote:
> From: Arınç ÜNAL <arinc.unal@...nc9.com>
> 
> The crystal frequency concerns the switch core. The frequency should be
> checked when the switch is being set up so the driver can reject the
> unsupported hardware earlier and without requiring port 6 to be used.
> 
> Move it to mt7530_setup().
> 
> Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
> ---

Do you know why a crystal frequency of 20 MHz is not supported?

>  drivers/net/dsa/mt7530.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> index 049f7be0d790..fa48273269c4 100644
> --- a/drivers/net/dsa/mt7530.c
> +++ b/drivers/net/dsa/mt7530.c
> @@ -408,13 +408,6 @@ mt7530_setup_port6(struct dsa_switch *ds, phy_interface_t interface)
>  
>  	xtal = mt7530_read(priv, MT7530_HWTRAP) & HWTRAP_XTAL_MASK;
>  
> -	if (xtal == HWTRAP_XTAL_20MHZ) {
> -		dev_err(priv->dev,
> -			"%s: MT7530 with a 20MHz XTAL is not supported!\n",
> -			__func__);
> -		return -EINVAL;
> -	}
> -
>  	switch (interface) {
>  	case PHY_INTERFACE_MODE_RGMII:
>  		trgint = 0;
> @@ -2133,7 +2126,7 @@ mt7530_setup(struct dsa_switch *ds)
>  	struct mt7530_dummy_poll p;
>  	phy_interface_t interface;
>  	struct dsa_port *cpu_dp;
> -	u32 id, val;
> +	u32 id, val, xtal;
>  	int ret, i;
>  
>  	/* The parent node of master netdev which holds the common system
> @@ -2203,6 +2196,15 @@ mt7530_setup(struct dsa_switch *ds)
>  		return -ENODEV;
>  	}
>  
> +	xtal = mt7530_read(priv, MT7530_HWTRAP) & HWTRAP_XTAL_MASK;
> +
> +	if (xtal == HWTRAP_XTAL_20MHZ) {
> +		dev_err(priv->dev,
> +			"%s: MT7530 with a 20MHz XTAL is not supported!\n",
> +			__func__);

I don't think __func__ brings much value here, it could be dropped in
the process of moving the code.

Also, the HWTRAP register is already read once, here (stored in "val"):

	INIT_MT7530_DUMMY_POLL(&p, priv, MT7530_HWTRAP);
	ret = readx_poll_timeout(_mt7530_read, &p, val, val != 0,
				 20, 1000000);

I wonder if we really need to read it twice.

> +		return -EINVAL;
> +	}
> +
>  	/* Reset the switch through internal reset */
>  	mt7530_write(priv, MT7530_SYS_CTRL,
>  		     SYS_CTRL_PHY_RST | SYS_CTRL_SW_RST |
> -- 
> 2.39.2
>