linux-kernel - Re: [PATCH 04/10] rtc: at91rm9200: use of_platform

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Message-ID: <04264cb0-61a9-aba3-82ad-e7d12fd8441e@microchip.com>
Date:   Wed, 18 Dec 2019 16:52:21 +0000
From:   <Eugen.Hristev@...rochip.com>
To:     <alexandre.belloni@...tlin.com>
CC:     <jic23@...nel.org>, <robh+dt@...nel.org>,
        <Nicolas.Ferre@...rochip.com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-rtc@...r.kernel.org>,
        <a.zummo@...ertech.it>, <Ludovic.Desroches@...rochip.com>
Subject: Re: [PATCH 04/10] rtc: at91rm9200: use of_platform_populate as return
 value



On 18.12.2019 18:43, Alexandre Belloni wrote:

> Hi,
> 
> On 18/12/2019 16:24:00+0000, Eugen.Hristev@...rochip.com wrote:
>> From: Eugen Hristev <eugen.hristev@...rochip.com>
>>
>> This allows the RTC node to have child nodes in DT.
>> This allows subnodes to be probed.
>>
>> Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
>> ---
>>   drivers/rtc/rtc-at91rm9200.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/rtc/rtc-at91rm9200.c b/drivers/rtc/rtc-at91rm9200.c
>> index 3b833e0..f1b5b3d 100644
>> --- a/drivers/rtc/rtc-at91rm9200.c
>> +++ b/drivers/rtc/rtc-at91rm9200.c
>> @@ -421,7 +421,7 @@ static int __init at91_rtc_probe(struct platform_device *pdev)
>>        at91_rtc_write_ier(AT91_RTC_SECEV);
>>
>>        dev_info(&pdev->dev, "AT91 Real Time Clock driver.\n");
>> -     return 0;
>> +     return of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
>>
> 
> You can avoid the DT binding change and DT parsing by using
> platform_add_device here. I don't think there is any point describing
> the trigger as a child node (a watchdog functionality wouldn't be
> described for example).
> 

Hi,

It's needed because the ADC needs a link to the trigger device. This is 
a hardware link inside the SoC, so I thought the best way is to describe 
this hardware is in the Device Tree.
Otherwise the ADC node is unaware of the RTC triggering possibility.
If we just assign the RTC trigger device to the ADC through the sysfs, 
the ADC cannot distinguish between the RTC trigger and other various 
triggers which can be attached.

> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
>