Re: [PATCH 15/17] i3c: master: Introduce optional Runtime PM support

From: Adrian Hunter <adrian.hunter@intel.com>
To: Frank Li <Frank.li@nxp.com>
Cc: <alexandre.belloni@bootlin.com>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	Aniket <aniketmaurya@google.com>, <linux-i3c@lists.infradead.org>,
	<miquel.raynal@bootlin.com>
Subject: Re: [PATCH 15/17] i3c: master: Introduce optional Runtime PM support
Date: Sat, 20 Dec 2025 16:50:40 +0200	[thread overview]
Message-ID: <a9d2b023-46c7-4dba-b453-2e82948188e7@intel.com> (raw)
In-Reply-To: <aUWGhscb+6ZYRhzx@lizhi-Precision-Tower-5810>

On 19/12/2025 19:08, Frank Li wrote:
> On Fri, Dec 19, 2025 at 04:45:32PM +0200, Adrian Hunter wrote:
>> Master drivers currently manage Runtime PM individually, but all require
>> runtime resume for bus operations.  This can be centralized in common code.
>>
>> Add optional Runtime PM support to ensure the parent device is runtime
>> resumed before bus operations and auto-suspended afterward.
>>
>> Notably, do not call ->bus_cleanup() if runtime resume fails.  Master
>> drivers that opt-in to core runtime PM support must take that into account.
>>
>> Also provide an option to allow IBIs and hot-joins while runtime suspended.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>> ---
>>  drivers/i3c/device.c       | 46 +++++++++++++++++--
>>  drivers/i3c/internals.h    |  4 ++
>>  drivers/i3c/master.c       | 93 +++++++++++++++++++++++++++++++++++---
>>  include/linux/i3c/master.h |  4 ++
>>  4 files changed, 138 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/i3c/device.c b/drivers/i3c/device.c
>> index 8a156f5ad692..101eaa77de68 100644
>> --- a/drivers/i3c/device.c
>> +++ b/drivers/i3c/device.c
>> @@ -46,10 +46,16 @@ int i3c_device_do_xfers(struct i3c_device *dev, struct i3c_xfer *xfers,
>>  			return -EINVAL;
>>  	}
>>
>> +	ret = i3c_bus_rpm_get(dev->bus);
> 
> Is it i3c_bus_rpm_get(dev)?  dev->bus is parent of dev. in case i3c
> periphal need enable clock or other run time pm enable call back?
> 
>> +	if (ret)
>> +		return ret;
>> +
>>  	i3c_bus_normaluse_lock(dev->bus);
>>  	ret = i3c_dev_do_xfers_locked(dev->desc, xfers, nxfers, mode);
>>  	i3c_bus_normaluse_unlock(dev->bus);
>>
>> +	i3c_bus_rpm_put(dev->bus);
>> +
>>  	return ret;
>>  }
> ...
>>
>> +static int __must_check i3c_master_rpm_get(struct i3c_master_controller *master)
>> +{
>> +	int ret = master->rpm_allowed ? pm_runtime_resume_and_get(master->dev.parent) : 0;
> 
> I think rpm_allowed is not necessary. If don't allow rpm,  i3c bus driver
> should disable runtime_pm.
> 
> I remember pm_runtime_resume_and_get() do nothing if runtime_pm disabled
> (need double check).

Yes that would be OK for drivers that do not enable runtime PM,
but the drivers that do enable runtime PM (i.e. dw-i3c-master.c
and svc-i3c-master.c) might be affected.

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