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

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Date: Tue, 8 Aug 2023 08:44:26 +0000
From: Wei Fang <wei.fang@....com>
To: Marek Vasut <marex@...x.de>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: "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>, Oleksij Rempel <linux@...pel-privat.de>,
	Paolo Abeni <pabeni@...hat.com>, Russell King <linux@...linux.org.uk>
Subject: RE: [PATCH] net: phy: at803x: Improve hibernation support on start up

Hi Marek,

> Toggle hibernation mode OFF and ON to wake the PHY up and make it
> generate clock on RX_CLK pin for about 10 seconds.
> These clock are needed during start up by MACs like DWMAC in NXP i.MX8M
> Plus to release their DMA from reset. After the MAC has started up, the PHY
> can enter hibernation and disable the RX_CLK clock, this poses no problem for
> the MAC.
> 
> Originally, this issue has been described by NXP in commit
> 9ecf04016c87 ("net: phy: at803x: add disable hibernation mode support") but
> this approach fully disables the hibernation support and takes away any power
> saving benefit. This patch instead makes the PHY generate the clock on start
> up for 10 seconds, which should be long enough for the EQoS MAC to release
> DMA from reset.
> 
> Before this patch on i.MX8M Plus board with AR8031 PHY:
> "
> $ ifconfig eth1 up
> [   25.576734] imx-dwmac 30bf0000.ethernet eth1: Register
> MEM_TYPE_PAGE_POOL RxQ-0
> [   25.658916] imx-dwmac 30bf0000.ethernet eth1: PHY [stmmac-1:00]
> driver [Qualcomm Atheros AR8031/AR8033] (irq=38)
> [   26.670276] imx-dwmac 30bf0000.ethernet: Failed to reset the dma
> [   26.676322] imx-dwmac 30bf0000.ethernet eth1: stmmac_hw_setup:
> DMA engine initialization failed
> [   26.685103] imx-dwmac 30bf0000.ethernet eth1: __stmmac_open: Hw
> setup failed
> ifconfig: SIOCSIFFLAGS: Connection timed out "
> 

Have you reproduced this issue based on the upstream net-next or net tree?
If so, can this issue be reproduced? The reason why I ask this is because when
I tried to reproduce this problem on net-next 6.3.0 version, I found that it could
not be reproduced (I did not disable hibernation mode when I reproduced this
issue ). So I guess maybe other patches in eqos driver fixed the issue.