netdev - Re: [PATCH net-next v1 2/4] net: phy: micrel: add EEE configuration support for KSZ9477 variants of PHYs

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Message-ID: <c45aa954-0931-1829-459f-8771faf05173@gmail.com>
Date:   Fri, 20 Jan 2023 09:58:05 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...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>, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Arun.Ramadoss@...rochip.com
Subject: Re: [PATCH net-next v1 2/4] net: phy: micrel: add EEE configuration
 support for KSZ9477 variants of PHYs



On 1/19/2023 9:55 PM, Oleksij Rempel wrote:
> On Thu, Jan 19, 2023 at 11:25:42AM -0800, Florian Fainelli wrote:
>> On 1/19/23 05:18, Oleksij Rempel wrote:
>>> KSZ9477 variants of PHYs are not completely compatible with generic
>>> phy_ethtool_get/set_eee() handlers. For example MDIO_PCS_EEE_ABLE acts
>>> like a mirror of MDIO_AN_EEE_ADV register. If MDIO_AN_EEE_ADV set to 0,
>>> MDIO_PCS_EEE_ABLE will be 0 too. It means, if we do
>>> "ethtool --set-eee lan2 eee off", we won't be able to enable it again.
>>>
>>> With this patch, instead of reading MDIO_PCS_EEE_ABLE register, the
>>> driver will provide proper abilities.
>>
>> We have hooks in place already for PHY drivers with the form of the read_mmd
>> and write_mmd callbacks, did this somehow not work for you?
>>
>> Below is an example:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d88fd1b546ff19c8040cfaea76bf16aed1c5a0bb
>>
>> (here the register location is non-standard but the bit definitions within
>> that register are following the standard).
> 
> It will work for this PHY, but not allow to complete support for AR8035.
> AR8035 provides support for "SmartEEE" where  tx_lpi_enabled and
> tx_lpi_timer are optionally handled by the PHY, not by MAC.

Not sure I understand your reply here, this would appear to be a 
limitation that exists regardless of the current API defined, does that 
mean that you can make use of the phy_driver::{read,write}_mmd function 
calls and you will make a v2 that uses them, or something else entirely?
-- 
Florian