linux-kernel - Re: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata (DS80000754C)

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Message-ID: <8ea50868-8854-1b4a-b43d-253279fabdd4@gmail.com>
Date:   Tue, 29 Aug 2023 15:00:34 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Tristram.Ha@...rochip.com, olteanv@...il.com
Cc:     andrew@...n.ch, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, Woojung.Huh@...rochip.com, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        UNGLinuxDriver@...rochip.com, lukma@...x.de
Subject: Re: [PATCH 2/2] net: dsa: microchip: Provide Module 4 KSZ9477 errata
 (DS80000754C)

On 8/29/23 14:57, Tristram.Ha@...rochip.com wrote:
>> On Fri, Aug 25, 2023 at 06:48:41PM +0000, Tristram.Ha@...rochip.com wrote:
>>>>> IMHO adding functions to MMD modification would facilitate further
>>>>> development (for example LED setup).
>>>>
>>>> We already have some KSZ9477 specific initialization done in the Micrel
>>>> PHY driver under drivers/net/phy/micrel.c, can we converge on the PHY
>>>> driver which has a reasonable amount of infrastructure for dealing with
>>>> workarounds, indirect or direct MMD accesses etc.?
>>>
>>> Actually the internal PHY used in the KSZ9897/KSZ9477/KSZ9893 switches
>>> are special and only used inside those switches.  Putting all the switch
>>> related code in Micrel PHY driver does not really help.  When the switch
>>> is reset all those PHY registers need to be set again, but the PHY driver
>>> only executes those code during PHY initialization.  I do not know if
>>> there is a good way to tell the PHY to re-initialize again.
>>
>> Suppose there was a method to tell the PHY driver to re-initialize itself.
>> What would be the key points in which the DSA switch driver would need
>> to trigger that method? Where is the switch reset at runtime?
> 
> Currently the DSA switch driver loads independently and is then
> controlled by the main DSA driver.  The switch is reset during
> initialization, and later the PHYs are initialized.  I was talking
> hypothetically that the switch may need to be reset to correct some
> hardware problems, but then there may be no good way to tell the PHYs to
> re-initialize.

There is phy_init_hw() which will do just that.
-- 
Florian