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

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Message-ID: <7d2aacbe-9725-2c15-38b7-deb56184f82b@arinc9.com>
Date:   Thu, 25 May 2023 10:04:23 +0300
From:   Arınç ÜNAL <arinc.unal@...nc9.com>
To:     Vladimir Oltean <olteanv@...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>,
        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 24.05.2023 21:15, Vladimir Oltean wrote:
> 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?

I don't know, it just isn't.

https://github.com/BPI-SINOVOIP/BPI-R2-bsp/blob/master/linux-mt/drivers/net/ethernet/mediatek/gsw_mt7623.c#L1076

> 
>>   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.

Will do.

> 
> 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.

Likely not, good catch.

Arınç