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

[Marek Vasut <marex@denx.de>]

On 8/8/23 10:44, Wei Fang wrote:
> Hi Marek,

Hi,

>> 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?

On current linux-next next-20230808 so 6.5.0-rc5 . As far as I can tell, 
net-next is merged into this tree too.

> 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.

This is what I use for testing:

- Make sure "qca,disable-hibernation-mode" is NOT present in PHY DT node
- Boot the machine with NO ethernet cable plugged into the affected port
   (i.e. the EQoS port), this is important
- Make sure the EQoS MAC is not brought up e.g. by systemd-networkd or
   whatever other tool, I use busybox initramfs for testing with plain
   script as init (it mounts the various filesystems and runs /bin/sh)
- Wait longer than 10 seconds
- If possible, measure AR8031 PHY pin 33 RX_CLK, wait for the RX_CLK to
   be turned OFF by the PHY (means PHY entered hibernation)
- ifconfig ethN up -- try to bring up the EQoS MAC
<observe failure>

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