linux-kernel - Re: [PATCH 4/4] rtc: imx-sm-bbm: Support multiple RTCs

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Message-ID: <20250212064117.GC15796@localhost.localdomain>
Date: Wed, 12 Feb 2025 14:41:17 +0800
From: Peng Fan <peng.fan@....nxp.com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: Cristian Marussi <cristian.marussi@....com>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	arm-scmi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-rtc@...r.kernel.org, Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 4/4] rtc: imx-sm-bbm: Support multiple RTCs

On Tue, Feb 11, 2025 at 05:01:12PM +0000, Sudeep Holla wrote:
>On Mon, Jan 20, 2025 at 10:25:36AM +0800, Peng Fan (OSS) wrote:
>> From: Peng Fan <peng.fan@....com>
>> 
>> i.MX95 EVK has two RTCs exported by SCMI BBM protocol. Current driver
>> only enables the 1st RTC inside BBNSM module, leaving the board RTC
>> not used by Linux.
>> 
>> To use the 2nd RTC, use 'bbm_info' to get the number of RTCs, register
>> them all, and set 'bbnsm' as private info for rtc device to know which
>> RTC it is when using rtc_class_ops to access rtc device.
>> 
>> Signed-off-by: Peng Fan <peng.fan@....com>
>> ---
>>  drivers/rtc/rtc-imx-sm-bbm.c | 69 +++++++++++++++++++++++++++-----------------
>>  1 file changed, 43 insertions(+), 26 deletions(-)
>> 
>> diff --git a/drivers/rtc/rtc-imx-sm-bbm.c b/drivers/rtc/rtc-imx-sm-bbm.c
>> index daa472be7c80697aa3cd3432eccef0c877e4c378..a29b30555d0c0581ecaa8b79760209dc780d2f0e 100644
>> --- a/drivers/rtc/rtc-imx-sm-bbm.c
>> +++ b/drivers/rtc/rtc-imx-sm-bbm.c
>> @@ -15,16 +15,18 @@ struct scmi_imx_bbm {
>>  	struct rtc_device *rtc_dev;
>>  	struct scmi_protocol_handle *ph;
>>  	struct notifier_block nb;
>> +	u32 bbm_rtc_id;
>
>Is it not same as rtc_dev->id ? Why do you need a copy in this wrapper/
>container structure ?

In theroy yes. The current system I use that all RTCs are managed by BBM
protocol. So only two RTCs are registered.

In case there is other RTCs that not managed BBM, the rtc_dev->id
will not be equal to bbm_rtc_id.

For example RTC1 is directly managed by Linux, RTC0 is managed by BBM.

The RTC1 is probed first, so its rtc_dev->id is 0. But from BBM protocol,
the RTC0 use id 0 for BBM SCMI server to handle the RTC0.

I maybe overthinking here. But to avoid potential issues, I would like to
keep bbm_rtc_id.

Regards,
Peng

>
>-- 
>Regards,
>Sudeep