linux-kernel - Re: [PATCH net] net: phy: micrel: populate .soft

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Date: Fri, 5 Jan 2024 15:36:29 +0100
From: Andrew Lunn <andrew@...n.ch>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Claudiu <claudiu.beznea@...on.dev>, hkallweit1@...il.com,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, yuiko.oshino@...rochip.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH net] net: phy: micrel: populate .soft_reset for KSZ9131

On Fri, Jan 05, 2024 at 09:43:22AM +0000, Russell King (Oracle) wrote:
> On Fri, Jan 05, 2024 at 10:52:42AM +0200, Claudiu wrote:
> > The order of PHY-related operations in ravb_open() is as follows:
> > ravb_open() ->
> >   ravb_phy_start() ->
> >     ravb_phy_init() ->
> >       of_phy_connect() ->
> >         phy_connect_direct() ->
> > 	  phy_attach_direct() ->
> > 	    phy_init_hw() ->
> > 	      phydev->drv->soft_reset()
> > 	      phydev->drv->config_init()
> > 	      phydev->drv->config_intr()
> > 	    phy_resume()
> > 	      kszphy_resume()
> > 
> > The order of PHY-related operations in ravb_close is as follows:
> > ravb_close() ->
> >   phy_stop() ->
> >     phy_suspend() ->
> >       kszphy_suspend() ->
> >         genphy_suspend()
> > 	  // set BMCR_PDOWN bit in MII_BMCR
> 
> Andrew,
> 
> This looks wrong to me - shouldn't we be resuming the PHY before
> attempting to configure it?

Hummm. The opposite of phy_stop() is phy_start(). So it would be the
logical order to perform the resume as the first action of
phy_start(), not phy_attach_direct().

In phy_connect_direct(), we don't need the PHY to be operational
yet. That happens with phy_start().

The standard says:

  22.2.4.1.5 Power down

  The PHY may be placed in a low-power consumption state by setting
  bit 0.11 to a logic one. Clearing bit 0.11 to zero allows normal
  operation. The specific behavior of a PHY in the power-down state is
  implementation specific. While in the power-down state, the PHY
  shall respond to management transactions.

So i would say this PHY is broken, its not responding to all
management transactions. So in that respect, Claudiu fix is correct.

But i also somewhat agree with you, this looks wrong, but in a
different way to how you see it. However, moving the phy_resume() to
phy_start() seems a bit risky. So i'm not sure we should actually do
that.

	Andrew