linux-kernel - Re: [PATCH] net: phy: mscc: enable MAC SerDes autonegotiation

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Date:   Mon, 28 Mar 2022 13:43:51 +0530
From:   Siddharth Vadapalli <s-vadapalli@...com>
To:     Raag Jadav <raagjadav@...il.com>
CC:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Steen Hegelund <steen.hegelund@...rochip.com>,
        Bjarni Jonasson <bjarni.jonasson@...rochip.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: phy: mscc: enable MAC SerDes autonegotiation

Hi Raag,

On 27/03/22 14:00, Raag Jadav wrote:
> On Thu, Mar 24, 2022 at 03:36:02PM +0530, Siddharth Vadapalli wrote:
>> Hi Raag,
>>
>> On 26/02/22 12:53, Raag Jadav wrote:
>>> On Thu, Feb 24, 2022 at 10:48:57AM +0000, Russell King (Oracle) wrote:
>>>> Sorry for the late comment on this patch.
>>>>
>>>> On Sat, Feb 05, 2022 at 12:14:52PM +0530, Raag Jadav wrote:
>>>>> +static int vsc85xx_config_inband_aneg(struct phy_device *phydev, bool enabled)
>>>>> +{
>>>>> +	int rc;
>>>>> +	u16 reg_val = 0;
>>>>> +
>>>>> +	if (enabled)
>>>>> +		reg_val = MSCC_PHY_SERDES_ANEG;
>>>>> +
>>>>> +	mutex_lock(&phydev->lock);
>>>>> +
>>>>> +	rc = phy_modify_paged(phydev, MSCC_PHY_PAGE_EXTENDED_3,
>>>>> +			      MSCC_PHY_SERDES_PCS_CTRL, MSCC_PHY_SERDES_ANEG,
>>>>> +			      reg_val);
>>>>> +
>>>>> +	mutex_unlock(&phydev->lock);
>>>>
>>>> What is the reason for the locking here?
>>>>
>>>> phy_modify_paged() itself is safe due to the MDIO bus lock, so you
>>>> shouldn't need locking around it.
>>>>
>>>
>>> True.
>>>
>>> My initial thought was to have serialized access at PHY level,
>>> as we have multiple ports to work with.
>>> But I guess MDIO bus lock could do the job as well.
>>>
>>> Will fix it in v2 if required.
>>
>> Could you please let me know if you plan to post the v2 patch?
>>
>> The autonegotiation feature is also required for VSC8514, and has to be invoked
>> in vsc8514_config_init(). Let me know if you need my help for this.
>>
> 
> Maybe this is what you're looking for.
> https://www.spinics.net/lists/netdev/msg768517.html

Thank you for pointing me to the thread. I will follow up regarding the progress
of the autonegotiation feature on that thread.

Regards,
Siddharth