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

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Message-ID: <Z6x7lemv2y8iMZZA@bogus>
Date: Wed, 12 Feb 2025 10:44:37 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Peng Fan <peng.fan@....nxp.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 Wed, Feb 12, 2025 at 02:41:17PM +0800, Peng Fan wrote:
> 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.
> 

Fair enough, I didn't think of this mix(firmware controlled RTC + Linux
controlled ones).

--
Regards,
Sudeep