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

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Date: Wed, 10 Jan 2024 15:20:19 +0200
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Andrew Lunn <andrew@...n.ch>,
 "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: 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

Hi, Andrew, Russell,

On 05.01.2024 16:36, Andrew Lunn wrote:
> 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.

It's not clear to me if you both agree with this fix. Could you please let
me know?

Thank you,
Claudiu Beznea

> 
> 	Andrew