linux-kernel - Re: [PATCH] ARM: dts: at91: add serial MFD sub-node for usart

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Message-ID: <f370bbf7-5cfc-1524-8103-061698ba6b67@microchip.com>
Date:   Fri, 30 Oct 2020 14:24:24 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <Nicolas.Ferre@...rochip.com>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <richard.genoud@...il.com>,
        <lee.jones@...aro.org>
CC:     <alexandre.belloni@...tlin.com>, <Ludovic.Desroches@...rochip.com>
Subject: Re: [PATCH] ARM: dts: at91: add serial MFD sub-node for usart

On 30.10.2020 15:38, Nicolas Ferre wrote:
> On 30/10/2020 at 12:07, Codrin Ciubotariu wrote:
>> The "atmel,at91sam9260-usart" driver is a MFD driver, so it needs 
>> sub-nodes
>> to match the registered platform device. For this reason, we add a serial
>> subnode to all the "atmel,at91sam9260-usart" serial compatible nods. This
>> will also remove the boot warning:
>> "atmel_usart_serial: Failed to locate of_node [id: -2]"
> 
> I don't remember this warning was raised previously even if the MFD 
> driver was added a while ago (Sept. 2018).
> 
> I would say it's due to 466a62d7642f ("mfd: core: Make a best effort 
> attempt to match devices with the correct of_nodes") which was added on 
> mid August and corrected with 22380b65dc70 ("mfd: mfd-core: Ensure 
> disabled devices are ignored without error") but maybe not covering our 
> case.

Well, it's not covering our enabled devices.

> 
> So, well, I don't know what's the best option to this change. Moreover, 
> I would say that all other USART related properties go into the child 
> not if there is a need for one.
> 
> Lee, I suspect that we're not the only ones experiencing this ugly 
> warning during the boot log: can you point us out how to deal with it 
> for our existing atmel_serial.c users?

My understading is that platform devices registered by MFD should have a 
correspondig DT node. The parrent properties are also available for the 
other usart device (usart-spi), so I think we should keep them in the 
parrent.

Best regards,
Codrin