netdev - Re: [PATCH net] net: bcmgenet: Fix EEE implementation

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Date: Tue, 6 Jun 2023 15:16:03 -0700
From: Florian Fainelli <florian.fainelli@...adcom.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: netdev@...r.kernel.org, o.rempel@...gutronix.de, andrew@...n.ch,
 hkallweit1@...il.com, Doug Berger <opendmb@...il.com>,
 Florian Fainelli <f.fainelli@...il.com>,
 Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net: bcmgenet: Fix EEE implementation

On 6/6/23 15:02, Russell King (Oracle) wrote:
> On Tue, Jun 06, 2023 at 02:43:47PM -0700, Florian Fainelli wrote:
>> We had a number of short comings:
>>
>> - EEE must be re-evaluated whenever the state machine detects a link
>>    change as wight be switching from a link partner with EEE
>>    enabled/disabled
>>
>> - tx_lpi_enabled controls whether EEE should be enabled/disabled for the
>>    transmit path, which applies to the TBUF block
>>
>> - We do not need to forcibly enable EEE upon system resume, as the PHY
>>    state machine will trigger a link event that will do that, too
>>
>> Fixes: 6ef398ea60d9 ("net: bcmgenet: add EEE support")
>> Signed-off-by: Florian Fainelli <florian.fainelli@...adcom.com>
>> ---
>> netdev maintainers, please do not apply without Andrew, Russell and
>> Oleksij reviewing first since this relates to the on-going EEE rework
>> from Andrew.
> 
> Hi Florian,
> 
> Please could you include some information on the UMAC_EEE_CTRL EEE_EN
> bit - is this like the main switch for EEE which needs to be set
> along with the bits in the tbuf register for the transmit side to
> signal LPI?

EEE_EN is described as:

If set, the TX LPI policy control engine is enabled and the MAC inserts 
LPI_idle codes if the link is idle. The rx_lpi_detect assertion is 
independent of this configuration.

in the RBUF, EEE_EN is described as:

1: to enable Energy Efficient feature between Unimac and PHY for Rx Path

and in the TBUF, EEE_EN is described as:

1: to enable Energy Efficient feature between Unimac and PHY for Tx Path

The documentation is unfortunately scare about how these two signals 
connect :/
-- 
Florian

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