linux-kernel - Re: [RFC PATCH net v1] net: phy: aquantia: Set phy speed to 2.5gbps for AQR115c

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Message-ID: <4b6addfe-5a54-41f8-9353-4541440950e9@quicinc.com>
Date: Fri, 13 Sep 2024 10:22:06 -0700
From: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>
To: Andrew Lunn <andrew@...n.ch>
CC: Maxime Chevallier <maxime.chevallier@...tlin.com>,
        "David S. Miller"
	<davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Andrew Halaney <ahalaney@...hat.com>,
        "Russell King (Oracle)" <linux@...linux.org.uk>,
        Heiner Kallweit
	<hkallweit1@...il.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Brad Griffis
	<bgriffis@...dia.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Jon Hunter
	<jonathanh@...dia.com>, <kernel@...cinc.com>
Subject: Re: [RFC PATCH net v1] net: phy: aquantia: Set phy speed to 2.5gbps
 for AQR115c



On 9/13/2024 9:35 AM, Andrew Lunn wrote:
> On Fri, Sep 13, 2024 at 09:12:13AM -0700, Abhishek Chauhan (ABC) wrote:
>>
>>
>> On 9/13/2024 1:01 AM, Maxime Chevallier wrote:
>>> Hi,
>>>
>>> On Thu, 12 Sep 2024 18:16:35 -0700
>>> Abhishek Chauhan <quic_abchauha@...cinc.com> wrote:
>>>
>>>> Recently we observed that aquantia AQR115c always comes up in
>>>> 100Mbps mode. AQR115c aquantia chip supports max speed up to
>>>> 2.5Gbps. Today the AQR115c configuration is done through
>>>> aqr113c_config_init which internally calls aqr107_config_init.
>>>> aqr113c and aqr107 are both capable of 10Gbps. Whereas AQR115c
>>>> supprts max speed of 2.5Gbps only.
>>>>
>>>> Fixes: 0ebc581f8a4b ("net: phy: aquantia: add support for aqr115c")
>>>> Signed-off-by: Abhishek Chauhan <quic_abchauha@...cinc.com>
>>>> ---
>>>>  drivers/net/phy/aquantia/aquantia_main.c | 7 +++++++
>>>>  1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/drivers/net/phy/aquantia/aquantia_main.c b/drivers/net/phy/aquantia/aquantia_main.c
>>>> index e982e9ce44a5..9afc041dbb64 100644
>>>> --- a/drivers/net/phy/aquantia/aquantia_main.c
>>>> +++ b/drivers/net/phy/aquantia/aquantia_main.c
>>>> @@ -499,6 +499,12 @@ static int aqr107_config_init(struct phy_device *phydev)
>>>>  	if (!ret)
>>>>  		aqr107_chip_info(phydev);
>>>>  
>>>> +	/* AQR115c supports speed up to 2.5Gbps */
>>>> +	if (phydev->interface == PHY_INTERFACE_MODE_2500BASEX) {
>>>> +		phy_set_max_speed(phydev, SPEED_2500);
>>>> +		phydev->autoneg = AUTONEG_ENABLE;
>>>> +	}
>>>> +
>>>
>>> If I get your commit log right, the code above will also apply for
>>> ASQR107, AQR113 and so on, don't you risk breaking these PHYs if they
>>> are in 2500BASEX mode at boot?
>>>
>>
>> I was thinking of the same. That this might break something here for other Phy chip. 
>> As every phy shares the same config init. Hence the reason for RFC. 
>>
>>> Besides that, if the PHY switches between SGMII and 2500BASEX
>>> dynamically depending on the link speed, it could be that it's
>>> configured by default in SGMII, hence this check will be missed.
>>>
>>>
>> I think the better way is to have AQR115c its own config_init which sets 
>> the max speed to 2.5Gbps and then call aqr113c_config_init . 
> 

Noted!

> phy_set_max_speed(phydev, SPEED_2500) is something a MAC does, not a
> PHY. It is a way for the MAC to say is supports less than the PHY. I
> would say the current aqcs109_config_init() is doing this wrong.
> 
>>> Is the AQR115c in the same situation as AQR111 for example, where the
>>> PMA capabilities reported are incorrect ?
> 
> This is the approach to follow. The PHY registers should report what
> it is actually capable of. But some aquantia PHYs get this
> wrong. Please check if this is also true for your PHY. Look at what
> genphy_c45_pma_read_abilities() is doing.
> 
> You might need to implement a .get_feature callback for this PHY which
> first calls genphy_c45_pma_read_abilities() and then manually fixes up
> what the PHY gets wrong.
> 

Thanks alot Andrew. I will get back to you with my analysis on AQR115c 
phy. Most likely the pma abilities are reported incorrectly. 


> 	Andrew