linux-kernel - Re: [PATCH net-next v2 6/7] net: dsa: mt7530: do not set priv->p5_interface on mt7530_setup

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Date: Tue, 9 Jan 2024 14:42:45 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Daniel Golle <daniel@...rotopia.org>,
 Landen Chao <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>,
 Sean Wang <sean.wang@...iatek.com>, 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>,
 Frank Wunderlich <frank-w@...lic-files.de>,
 Bartel Eerdekens <bartel.eerdekens@...stell8.be>, mithat.guner@...ont.com,
 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: [PATCH net-next v2 6/7] net: dsa: mt7530: do not set
 priv->p5_interface on mt7530_setup_port5()

On 6.01.2024 18:00, Arınç ÜNAL wrote:
> On 4.01.2024 18:42, Vladimir Oltean wrote:
>> On Wed, Dec 27, 2023 at 07:43:46AM +0300, Arınç ÜNAL wrote:
>>> priv->p5_interface and priv->p6_interface are for use on the MT7531 switch.
>>> They prevent the CPU ports of MT7531 to be configured again. They are
>>> useless for MT7530. Therefore, remove setting priv->p5_interface for
>>> MT7530.
>>>
>>> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
>>> ---
>>
>> What makes priv->p5_interface and priv->p6_interface useless for MT7530
>> as you say? This code in mt753x_phylink_mac_config() seems executed
>> regardless of switch family:
>>
>>     case 5:
>>         if (priv->p5_interface == state->interface)
>>             break;
>>
>>         if (mt753x_mac_config(ds, port, mode, state) < 0)
>>             goto unsupported;
>>
>>         if (priv->p5_intf_sel != P5_DISABLED)
>>             priv->p5_interface = state->interface;
>>         break;
>>     case 6:
>>         if (priv->p6_interface == state->interface)
>>             break;
>>
>>         mt753x_pad_setup(ds, state);
>>
>>         if (mt753x_mac_config(ds, port, mode, state) < 0)
>>             goto unsupported;
>>
>>         priv->p6_interface = state->interface;
>>         break;
> 
> This is also useless for non-MT7531 switches in the sense that it
> unnecessarily prevents port 5 and 6 from being reconfigured. There's
> nothing wrong with configuring them multiple times. These are the remains
> of before phylink was implemented on this driver so the thought of changing
> phy_interface_t on the fly was non existent. At that time, it was probably
> made to apply to all switch models for convenience, as port 5 and 6 are CPU
> ports so they're highly likely to be fixed links.
> 
> The reason I don't deal with this code block now is because I will get rid
> of priv->p5_interface and priv->p6_interface when I also get rid of
> priv->info->cpu_port_config() with a later patch.

Sorry, I couldn't give a straight answer. Here's the exact answer to this
patch.

Running mt7530_setup_port5() from mt7530_setup() handles all cases of
configuring port 5, including phylink.

Setting priv->p5_interface under mt7530_setup_port5() makes sure that
mt7530_setup_port5() from mt753x_phylink_mac_config() won't run.

The ("net: dsa: mt7530: improve code path for setting up port 5") patch
makes so that mt7530_setup_port5() from mt7530_setup() runs only on
non-phylink cases.

So we get rid of setting priv->p5_interface under mt7530_setup_port5() as
port 5 phylink configuration will be done by running mt7530_setup_port5()
from mt753x_phylink_mac_config() now.

Running mt7530_setup_port5() from mt753x_phylink_mac_config() multiple
times is being prevented which shouldn't be done. That's because of a
different reason involving MT7531. I will deal with this with a later
patch.

I intend to put this on the patch log.

Arınç