linux-kernel - Re: [PATCH net v3] net: phy: intel-xway: enable integrated led functions

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Date:   Fri, 4 Feb 2022 09:06:57 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Tim Harvey <tharvey@...eworks.com>
Cc:     Andrew Lunn <andrew@...n.ch>, Martin Schiller <ms@....tdt.de>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        martin.blumenstingl@...glemail.com, hkallweit1@...il.com,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        David Miller <davem@...emloft.net>, kuba@...nel.org,
        netdev <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v3] net: phy: intel-xway: enable integrated led
 functions



On 2/3/2022 8:02 AM, Tim Harvey wrote:
> On Wed, Feb 2, 2022 at 7:12 PM Florian Fainelli <f.fainelli@...il.com> wrote:
>>
>>
>>
>> On 2/2/2022 5:01 PM, Andrew Lunn wrote:
>>>> As a person responsible for boot firmware through kernel for a set of
>>>> boards I continue to do the following to keep Linux from mucking with
>>>> various PHY configurations:
>>>> - remove PHY reset pins from Linux DT's to keep Linux from hard resetting PHY's
>>>> - disabling PHY drivers
>>>>
>>>> What are your thoughts about this?
>>>
>>> Hi Tim
>>>
>>> I don't like the idea that the bootloader is controlling the hardware,
>>> not linux.
>>
>> This is really trying to take advantage of the boot loader setting
>> things up in a way that Linux can play dumb by using the Generic PHY
>> driver and being done with it. This works... until it stops, which
>> happens very very quickly in general. The perfect counter argument to
>> using the Generic PHY driver is when your system implements a low power
>> mode where the PHY loses its power/settings, comes up from suspend and
>> the strap configuration is insufficient and the boot loader is not part
>> of the resume path *prior* to Linux. In that case Linux needs to restore
>> the settings, but it needs a PHY driver for that.
> 
> Florian,
> 
> That makes sense - I'm always trying to figure out what the advantage
> of using some of these PHY drivers really is vs disabling them.
> 
>>
>> If your concern Tim is with minimizing the amount of time the link gets
>> dropped and re-established, then there is not really much that can be
>> done that is compatible with Linux setting things up, short of
>> minimizing the amount of register writes that do need the "commit phase"
>> via BMCR.RESET.
> 
> No, my reasoning has nothing to do with link time - I have just run
> into several cases where some new change in a PHY driver blatantly
> either resets the PHY reverting to pin-strapping config which is wrong
> (happend to me with DP83867 but replacing the 'reset' to a 'restart'
> solved that) or imposes some settings without dt bindings to guide it
> (this case with the LEDs) or imposes some settings based on 'new'
> dt-bindings which I was simply not aware of (a lesser issue as dt
> bindings can be added to resolve it).
> 
>>
>> I do agree that blindly imposing LED settings that are different than
>> those you want is not great, and should be remedied. Maybe you can
>> comment this part out in your downstream tree for a while until the LED
>> binding shows up (we have never been so close I am told).
> 
> or disable the driver in defconfig, or blacklist the module if I want
> to do it via rootfs.
> 
> Can you point me to something I can look at for these new LED bindings
> that are being worked on?
> 

This is the latest attempt AFAICT:

https://lore.kernel.org/netdev/20211112153557.26941-1-ansuelsmth@gmail.com/
-- 
Florian