linux-kernel - RE: [PATCH 02/11] i2c: imx-lpi2c: add runtime pm support

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Date:   Fri, 19 Mar 2021 06:16:26 +0000
From:   Clark Wang <xiaoning.wang@....com>
To:     Aisheng Dong <aisheng.dong@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
CC:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "sumit.semwal@...aro.org" <sumit.semwal@...aro.org>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "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 02/11] i2c: imx-lpi2c: add runtime pm support


> -----Original Message-----
> From: Aisheng Dong <aisheng.dong@....com>
> Sent: Friday, March 19, 2021 12:40
> To: Clark Wang <xiaoning.wang@....com>; shawnguo@...nel.org;
> s.hauer@...gutronix.de
> Cc: kernel@...gutronix.de; festevam@...il.com; dl-linux-imx <linux-
> imx@....com>; sumit.semwal@...aro.org; christian.koenig@....com;
> linux-i2c@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org
> Subject: RE: [PATCH 02/11] i2c: imx-lpi2c: add runtime pm support
>
> > From: Clark Wang <xiaoning.wang@....com>
> > Sent: Wednesday, March 17, 2021 2:54 PM
> > Subject: [PATCH 02/11] i2c: imx-lpi2c: add runtime pm support
> >
> > - Add runtime pm support to dynamicly manage the clock.
> > - Put the suspend to suspend_noirq.
> > - Call .pm_runtime_force_suspend() to force runtime pm suspended
> >   in .suspend_noirq().
> >
>
> The patch title needs to be improved as the driver already supports rpm.
> And do one thing in one patch.
>
> > Signed-off-by: Fugang Duan <fugang.duan@....com>
> > Signed-off-by: Gao Pan <pandy.gao@....com>
> > Reviewed-by: Anson Huang <Anson.Huang@....com>
>
> Please add your sign-off.
>
> > ---
> >  drivers/i2c/busses/i2c-imx-lpi2c.c | 50
> > ++++++++++++++++++++----------
> >  1 file changed, 33 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > index bbf44ac95021..1e920e7ac7c1 100644
> > --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> > +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> > @@ -574,7 +574,8 @@ static int lpi2c_imx_probe(struct platform_device
> > *pdev)
> >  	if (ret)
> >  		lpi2c_imx->bitrate = I2C_MAX_STANDARD_MODE_FREQ;
> >
> > -	ret = devm_request_irq(&pdev->dev, irq, lpi2c_imx_isr, 0,
> > +	ret = devm_request_irq(&pdev->dev, irq, lpi2c_imx_isr,
> > +			       IRQF_NO_SUSPEND,
>
> This belongs to a separate patch
>
> >  			       pdev->name, lpi2c_imx);
> >  	if (ret) {
> >  		dev_err(&pdev->dev, "can't claim irq %d\n", irq); @@ -
> 584,35
> > +585,32 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
> >  	i2c_set_adapdata(&lpi2c_imx->adapter, lpi2c_imx);
> >  	platform_set_drvdata(pdev, lpi2c_imx);
> >
> > -	ret = clk_prepare_enable(lpi2c_imx->clk);
> > -	if (ret) {
> > -		dev_err(&pdev->dev, "clk enable failed %d\n", ret);
> > -		return ret;
> > -	}
> > -
> >  	pm_runtime_set_autosuspend_delay(&pdev->dev,
> I2C_PM_TIMEOUT);
> >  	pm_runtime_use_autosuspend(&pdev->dev);
> > -	pm_runtime_get_noresume(&pdev->dev);
> > -	pm_runtime_set_active(&pdev->dev);
> >  	pm_runtime_enable(&pdev->dev);
> >
> > +	ret = pm_runtime_get_sync(&pdev->dev);
> > +	if (ret < 0) {
> > +		pm_runtime_put_noidle(&pdev->dev);
> > +		dev_err(&pdev->dev, "failed to enable clock\n");
> > +		return ret;
> > +	}
>
> Can't current clk control via rpm work well?
> Please describe why need change.

I think the previous patch maker might want to use the return value of 
pm_runtime_get_sync to check whether the clock has been turned on correctly to 
avoid the kernel panic.
Maybe I can change to the method like this.
	pm_runtime_get_noresume(&pdev->dev);
	ret = pm_runtime_set_active(&pdev->dev);
	if (ret < 0)
		goto out;
	pm_runtime_enable(&pdev->dev);

Best Regards,
Clark Wang


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