netdev - Re: [RFC PATCH net-next 20/22] net: dsa: mt7530: force link-down on MACs before reset on MT7530

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Date:   Sat, 29 Apr 2023 18:37:18 +0300
From:   Arınç ÜNAL <arinc.unal@...nc9.com>
To:     Daniel Golle <daniel@...rotopia.org>
Cc:     Sean Wang <sean.wang@...iatek.com>,
        Landen Chao <Landen.Chao@...iatek.com>,
        DENG Qingfang <dqfext@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...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>,
        erkin.bozoglu@...ont.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [RFC PATCH net-next 20/22] net: dsa: mt7530: force link-down on
 MACs before reset on MT7530

On 21.04.2023 21:42, Daniel Golle wrote:
> On Fri, Apr 21, 2023 at 05:36:46PM +0300, arinc9.unal@...il.com wrote:
>> From: Arınç ÜNAL <arinc.unal@...nc9.com>
>>
>> Force link-down on all MACs before internal reset. Let's follow suit commit
>> 728c2af6ad8c ("net: mt7531: ensure all MACs are powered down before
>> reset").
>>
>> Tested-by: Arınç ÜNAL <arinc.unal@...nc9.com>
>> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
>> ---
>>   drivers/net/dsa/mt7530.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
>> index ac1e3c58aaac..8ece3d0d820c 100644
>> --- a/drivers/net/dsa/mt7530.c
>> +++ b/drivers/net/dsa/mt7530.c
>> @@ -2203,6 +2203,10 @@ mt7530_setup(struct dsa_switch *ds)
>>   		return -EINVAL;
>>   	}
>>   
>> +	/* Force link-down on all MACs before internal reset */
>> +	for (i = 0; i < MT7530_NUM_PORTS; i++)
>> +		mt7530_write(priv, MT7530_PMCR_P(i), PMCR_FORCE_LNK);
>> +
> 
> Moving this part to mt753x_setup just before calling priv->info->sw_setup(ds);
> is probably better. Though it isn't documented I assume that the requirement
> to have the ports in force-link-down may also apply to MT7988, and for sure
> it doesn't do any harm.

Now that I'm reading through the programming guide for MT7531 [0] and 
MT7530 [1], I see that the SW_PHY_RST bit on the SYS_CTRL register 
doesn't exist for MT7531. This is likely why forcing link-down on the 
MACs is necessary for MT7531.

I didn't come across any documentation for the switch on the MT7988 SoC. 
Should I assume the registers are identical with MT7531 or have you got 
a document I can look at?

You also don't do system or register reset for the switch on the MT7988 
SoC, what's up with that?

I'm not going to do this change for MT7530 as I think SW_PHY_RST is 
sufficient, and there's no mention to this like on MT7531.

[0] 
https://drive.google.com/file/d/1aVdQz3rbKWjkvdga8-LQ-VFXjmHR8yf9/view?usp=sharing
[1] 
https://github.com/vschagen/documents/blob/main/MT7621_ProgrammingGuide_GSW_v0_3.pdf

Arınç