linux-kernel - Re: [PATCH 1/1] net: spacemit: Check netif_carrier

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Message-ID: <48757af2-bbea-4185-8cc9-2ef51dbc8373@lunn.ch>
Date: Mon, 19 Jan 2026 16:09:13 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Chukun Pan <amadeus@....edu.cn>
Cc: wangruikang@...as.ac.cn, andrew+netdev@...n.ch, davem@...emloft.net,
	dlan@...too.org, edumazet@...gle.com, kuba@...nel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
	netdev@...r.kernel.org, pabeni@...hat.com, spacemit@...ts.linux.dev
Subject: Re: [PATCH 1/1] net: spacemit: Check netif_carrier_ok when reading
 stats

> root@...nWrt:~# ethtool -S eth1
> [   71.725539] k1_emac cac81000.ethernet eth1: Read stat timeout
> NIC statistics:
>      rx_drp_fifo_full_pkts: 0
>      rx_truncate_fifo_full_pkts: 0
> 
> I just discovered that adding "motorcomm,auto-sleep-disabled" to disable
> the sleep mode of the MotorComm PHY prevents the problem from occurring.

This suggests that when the PHY stops the reference clock, the MAC
hardware stops working. It needs that clock to access
statistics. Keeping the clock ticking will increase power usage a
little.

I wounder if anything else stops working? There are some MACs whos DMA
engine stop working without the reference clock. That can cause
problems during both probe and remove, or open and close.

So it would be nice to have a better understanding of this. If this
turns out to be true, maybe a comment by this poll_read_timeout()
indicating if it does timeout, the PHY might be the problem.

	   Andrew