linux-kernel - Re: [PATCH] i2c: imx: make controller available until system suspend_noirq() and from resume

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Message-ID:
 <AM0PR0402MB3937ECA7D10662217F787AEBE8312@AM0PR0402MB3937.eurprd04.prod.outlook.com>
Date: Fri, 6 Dec 2024 09:13:16 +0000
From: Carlos Song <carlos.song@....com>
To: Andi Shyti <andi.shyti@...nel.org>
CC: "o.rempel@...gutronix.de" <o.rempel@...gutronix.de>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>, "shawnguo@...nel.org"
	<shawnguo@...nel.org>, "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
	"festevam@...il.com" <festevam@...il.com>, Frank Li <frank.li@....com>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: imx: make controller available until system
 suspend_noirq() and from resume_noirq()



> -----Original Message-----
> From: Andi Shyti <andi.shyti@...nel.org>
> Sent: Thursday, December 5, 2024 7:54 PM
> To: Carlos Song <carlos.song@....com>
> Cc: o.rempel@...gutronix.de; kernel@...gutronix.de; shawnguo@...nel.org;
> s.hauer@...gutronix.de; festevam@...il.com; Frank Li <frank.li@....com>;
> linux-i2c@...r.kernel.org; imx@...ts.linux.dev;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Subject: [EXT] Re: [PATCH] i2c: imx: make controller available until system
> suspend_noirq() and from resume_noirq()
> 
> Caution: This is an external email. Please take care when clicking links or
> opening attachments. When in doubt, report the message using the 'Report this
> email' button
> 
> 
> Hi Carlos,
> 
> ...
> 
> > +static int i2c_imx_suspend(struct device *dev) {
> > +     /*
> > +      * Some I2C devices may need I2C controller up during resume_noirq()
> > +      * or suspend_noirq(), if the controller is autosuspended, there is
> > +      * no way to wakeup it once runtime pm is disabled (in
> suspend_late()).
> > +      * When system resume, I2C controller will be available until runtime
> pm
> > +      * is enabled(in_resume_early()). But it is too late for some devices.
> > +      * Wakeup the controller in suspend() callback while runtime pm is
> enabled,
> > +      * I2C controller will be available until suspend_noirq() callback
> > +      * (pm_runtime_force_suspend()) is called. During the resume, I2C
> controller
> > +      * can be restored by resume_noirq() callback
> (pm_runtime_force_resume()).
> > +      * Then resume() callback enables autosuspend. It will make I2C
> controller
> > +      * available until system suspend_noirq() and from resume_noirq().
> > +      */
> 
> Just made some little adjustments to the comment above, please let me know if
> they are fine:
> 
>         /*
>          * Some I2C devices may need the I2C controller to remain active
>          * during resume_noirq() or suspend_noirq(). If the controller is
>          * autosuspended, there is no way to wake it up once runtime PM is
>          * disabled (in suspend_late()).
>          *
>          * During system resume, the I2C controller will be available only
>          * after runtime PM is re-enabled (in resume_early()). However, this
>          * may be too late for some devices.
>          *
>          * Wake up the controller in the suspend() callback while runtime PM
>          * is still enabled. The I2C controller will remain available until
>          * the suspend_noirq() callback (pm_runtime_force_suspend()) is
>          * called. During resume, the I2C controller can be restored by the
>          * resume_noirq() callback (pm_runtime_force_resume()).
>          *
>          * Finally, the resume() callback re-enables autosuspend, ensuring
>          * the I2C controller remains available until the system enters
>          * suspend_noirq() and from resume_noirq().
>          */
> 
> If so, I will take it in.
> 

Hi, Andi,

That is so nice!

> Andi
> 
> > +     return pm_runtime_resume_and_get(dev); }