linux-kernel - Re: [net-next] phylib: Add device reset GPIO support causes DSA MT7530 acquires reset-gpios fails

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Message-ID: <5cf08589-b4e4-3b4c-cc3e-c6100492155f@gmail.com>
Date:   Mon, 18 Dec 2017 11:21:29 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Sean Wang <sean.wang@...iatek.com>
Cc:     sergei.shtylyov@...entembedded.com,
        vivien.didelot@...oirfairelinux.com, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, richard.leitner@...data.com,
        geert+renesas@...der.be
Subject: Re: [net-next] phylib: Add device reset GPIO support causes DSA
 MT7530 acquires reset-gpios fails

On 12/18/2017 12:01 AM, Andrew Lunn wrote:
> Hi Sean
> 
>> It probably can't. Because before the GPIO line is manipulated to reset,
>> certain power control should be handled such as power sources from
>> external PMIC to let devices actually enter the proper state.
>>
>> So, I thought the kind of reset should be better controlled by the
>> specific driver, not by generic core.
> 
> Yes, the driver should do it in that case.
> 
> So we have a few choices:
> 
> 1) Change the name of one of the properties
> 
> 2) Make the new code look at the compatible string, any only apply a
>    reset if it is a PHY.
> 
> 3) Make the new code only hold the gpio when it needs it. Same for the
>    driver, so that they both can reset the device.
> 
> Any other ideas? Any preferences? 2) and 3) are probably simpler to
> do, less backwards compatibility issues. 3) potentially could cause
> issues when a device is reset in the wrong context, because of
> external PMIC etc. So i'm thinking 2).

We could also add some sort of flag that indicates whether the reset
should be managed by the core, or the driver, I would have to double
check there is not a chicken and egg problem and that the driver probe
is early enough this can happen...
-- 
Florian