linux-kernel - Re: [PATCH net-next] net: stmmac: dwmac-renesas-gbeth: Add PM suspend/resume callbacks

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Message-ID: <aGpLpLDPdcPByC7j@shell.armlinux.org.uk>
Date: Sun, 6 Jul 2025 11:10:44 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	"linux-stm32@...md-mailman.stormreply.com" <linux-stm32@...md-mailman.stormreply.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"biju.das.au" <biju.das.au@...il.com>
Subject: Re: [PATCH net-next] net: stmmac: dwmac-renesas-gbeth: Add PM
 suspend/resume callbacks

On Sun, Jul 06, 2025 at 09:55:28AM +0000, Biju Das wrote:
> Just adding some logs:
> Currently PHY resume is called twice
> [   35.754933]  kszphy_resume+0x3c/0xf0
> [   35.754940]  phy_resume+0x3c/0x74
> [   35.754949]  phylink_prepare_resume+0x58/0xa0
> [   35.754957]  stmmac_resume+0x90/0x2a0
> [   35.771296]  stmmac_pltfr_resume+0x3c/0x4c
> 
> and
> 
> [   35.771258]  kszphy_resume+0x3c/0xf0
> [   35.771263]  __phy_resume+0x28/0x54
> [   35.771270]  phy_start+0x7c/0xb4
> [   35.771275]  phylink_start+0xb8/0x210
> [   35.771282]  phylink_resume+0x7c/0xc4
> [   35.771288]  stmmac_resume+0x1ec/0x2a0
> [   35.771296]  stmmac_pltfr_resume+0x3c/0x4c

This shouldn't be a problem. Phylib will do this, and PHY drivers are
expected to cope.

For example, on non-MAC managed PM PHYs, mdio_bus_phy_resume() will
call phy_init_hw() followed by phy_resume(). If a MAC subsequently is
brought up, phy_start() will be called, which will also call
__phy_resume().

If this is upsetting the KSZ PHY, then the KSZ PHY driver needs fixing.

-- 
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