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

[Clark Wang]

> -----Original Message-----
> From: Clark Wang <xiaoning.wang at nxp.com>
> Sent: Friday, March 19, 2021 14:16
> To: Aisheng Dong <aisheng.dong at nxp.com>; shawnguo at kernel.org;
> s.hauer at pengutronix.de
> Cc: kernel at pengutronix.de; festevam at gmail.com; dl-linux-imx <linux-
> imx at nxp.com>; sumit.semwal at linaro.org; christian.koenig at amd.com;
> linux-i2c at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
> kernel at vger.kernel.org
> Subject: RE: [PATCH 02/11] i2c: imx-lpi2c: add runtime pm support
>
>
> > -----Original Message-----
> > From: Aisheng Dong <aisheng.dong at nxp.com>
> > Sent: Friday, March 19, 2021 12:40
> > To: Clark Wang <xiaoning.wang at nxp.com>; shawnguo at kernel.org;
> > s.hauer at pengutronix.de
> > Cc: kernel at pengutronix.de; festevam at gmail.com; dl-linux-imx <linux-
> > imx at nxp.com>; sumit.semwal at linaro.org; christian.koenig at amd.com;
> > linux-i2c at vger.kernel.org; linux-arm-kernel at lists.infradead.org; linux-
> > kernel at vger.kernel.org
> > Subject: RE: [PATCH 02/11] i2c: imx-lpi2c: add runtime pm support
> >
> > > From: Clark Wang <xiaoning.wang at nxp.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 at nxp.com>
> > > Signed-off-by: Gao Pan <pandy.gao at nxp.com>
> > > Reviewed-by: Anson Huang <Anson.Huang at nxp.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

Sorry, I missed the point before.
If we use pm_runtime_get_noresume(&pdev->dev); and 
pm_runtime_set_active(&pdev->dev); here, the clk should be enabled by using 
clk_prepare_enable() in the probe function. However, the call of 
clk_prepare_enable() is already in lpi2c_runtime_resume().
Using get_sync() here can help to reduce the repetitive code, especially ipg 
clk will be added later.
Shall we change to use pm_runtime_get_sync() here?

Regards,
Clark Wang


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