netdev - Re: [PATCH] net: phy: at803x: Improve hibernation support on start up

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Message-ID: <7aabc198-9df5-5bce-2968-90d4cda3c244@bootlin.com>
Date: Thu, 14 Dec 2023 09:13:58 +0100 (CET)
From: Romain Gantois <romain.gantois@...tlin.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
cc: Oleksij Rempel <o.rempel@...gutronix.de>, Wei Fang <wei.fang@....com>, 
    Marek Vasut <marex@...x.de>, 
    "netdev@...r.kernel.org" <netdev@...r.kernel.org>, 
    "David S. Miller" <davem@...emloft.net>, Andrew Lunn <andrew@...n.ch>, 
    Eric Dumazet <edumazet@...gle.com>, Heiner Kallweit <hkallweit1@...il.com>, 
    Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
    kernel@...gutronix.de, linux-clk@...r.kernel.org, 
    Stephen Boyd <sboyd@...nel.org>, 
    Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH] net: phy: at803x: Improve hibernation support on start
 up

Hello Russell,

On Thu, 10 Aug 2023, Russell King (Oracle) wrote:

> > We've had these issues before with stmmac, so this "stmmac needs the
> > PHY receive clock" is nothing new - it's had problems with system
> > suspend/resume in the past, and I've made suggestions... and when
> > there's been two people trying to work on it, I've attempted to get
> > them to talk to each other which resulted in nothing further
> > happening.
> > 
> > Another solution could possibly be that we reserve bit 30 on the
> > PHY dev_flags to indicate that the receive clock must always be
> > provided. I suspect that would have an advantage in another
> ...
> 
> Something like this for starters:
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> ...

I've implemented and tested the general-case solution you proposed to this 
receive clock issue with stmmac drivers. The core of your suggestion is pretty 
much unchanged, I just added a phylink_pcs flag for standalone PCS drivers that 
also need to provide the receive clock.

I'd like to send a series for this upstream, which would allow solving this 
issue for both the DWMAC RZN1 case and the AT803x PHY suspend/hibernate case 
(and also potentially other cases with a similar bug).

I wanted to ask you how you would prefer to be credited in my patch series. I 
was considering putting you as author and first signer of the initial patch 
adding the phy_dev flag. Would that be okay or would you prefer something else?

Best Regards,

-- 
Romain Gantois, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com