linux-kernel - Re: [PATCH net-next 1/2] net: dsa: mt7530-mdio: read PHY address of switch from device tree

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Message-ID: <6faf8008-3a64-4ed9-8d7e-52ff32862df9@wanadoo.fr>
Date: Sun, 14 Apr 2024 10:06:42 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Daniel Golle <daniel@...rotopia.org>, arinc.unal@...nc9.com
Cc: DENG Qingfang <dqfext@...il.com>, Sean Wang <sean.wang@...iatek.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>,
 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 1/2] net: dsa: mt7530-mdio: read PHY address of
 switch from device tree

Le 14/04/2024 à 05:10, Daniel Golle a écrit :
> On Sun, Apr 14, 2024 at 01:08:19AM +0300, Arınç ÜNAL via B4 Relay wrote:
>> From: Arınç ÜNAL <arinc.unal@...nc9.com>
>>
>> Read the PHY address the switch listens on from the reg property of the
>> switch node on the device tree. This change brings support for MT7530
>> switches on boards with such bootstrapping configuration where the switch
>> listens on a different PHY address than the hardcoded PHY address on the
>> driver, 31.
>>
>> As described on the "MT7621 Programming Guide v0.4" document, the MT7530
>> switch and its PHYs can be configured to listen on the range of 7-12,
>> 15-20, 23-28, and 31 and 0-4 PHY addresses.
>>
>> There are operations where the switch PHY registers are used. For the PHY
>> address of the control PHY, transform the MT753X_CTRL_PHY_ADDR constant
>> into a macro and use it. The PHY address for the control PHY is 0 when the
>> switch listens on 31. In any other case, it is one greater than the PHY
>> address the switch listens on.
>>
>> Signed-off-by: Arınç ÜNAL <arinc.unal@...nc9.com>
> 
> See minor nit inline below.
> 

..

>>   
>> -#define MT753X_CTRL_PHY_ADDR		0
>> +#define MT753X_CTRL_PHY_ADDR(phy_addr)	(phy_addr == 0x1f ? 0 : phy_addr + 1)
> 
> #define MT753X_CTRL_PHY_ADDR(phy_addr)	(phy_addr + 1 & 0x1f)

Nit: maybe (even if certainly useless in this case):
   #define MT753X_CTRL_PHY_ADDR(phy_addr)	((phy_addr) + 1 & 0x1f)

?

> 
> It's shorter, and works without conditional operator which is expensive.
> 

Cj