linux-kernel - RE: [PATCH v6 5/8] PCI: imx6: Refine the regulator usage

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Date:   Mon, 14 Feb 2022 04:52:25 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>
CC:     "l.stach@...gutronix.de" <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>
Subject: RE: [PATCH v6 5/8] PCI: imx6: Refine the regulator usage

> -----Original Message-----
> From: Hongxing Zhu
> Sent: 2022年2月14日 11:08
> To: Francesco Dolcini <francesco.dolcini@...adex.com>
> Cc: l.stach@...gutronix.de; bhelgaas@...gle.com; broonie@...nel.org;
> lorenzo.pieralisi@....com; jingoohan1@...il.com; festevam@...il.com;
> linux-pci@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> kernel@...gutronix.de
> Subject: RE: [PATCH v6 5/8] PCI: imx6: Refine the regulator usage
> 
> > -----Original Message-----
> > From: Francesco Dolcini <francesco.dolcini@...adex.com>
> > Sent: 2022年2月12日 0:28
> > To: Hongxing Zhu <hongxing.zhu@....com>
> > Cc: l.stach@...gutronix.de; bhelgaas@...gle.com; broonie@...nel.org;
> > lorenzo.pieralisi@....com; jingoohan1@...il.com; festevam@...il.com;
> > linux-pci@...r.kernel.org; dl-linux-imx <linux-imx@....com>;
> > linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> > kernel@...gutronix.de
> > Subject: Re: [PATCH v6 5/8] PCI: imx6: Refine the regulator usage
> >
> > Hello Richard,
> >
> > On Tue, Feb 08, 2022 at 11:25:32AM +0800, Richard Zhu wrote:
> > > The driver should undo any enables it did itself. The regulator
> > > disable shouldn't be basing decisions on regulator_is_enabled().
> > >
> > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > > ---
> > >  drivers/pci/controller/dwc/pci-imx6.c | 14 ++------------
> > >  1 file changed, 2 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > > b/drivers/pci/controller/dwc/pci-imx6.c
> > > index 0aca762d88a3..e165ad00989c 100644
> > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > @@ -369,8 +369,6 @@ static int imx6_pcie_attach_pd(struct device
> > > *dev)
> > >
> > >  static void imx6_pcie_assert_core_reset(struct imx6_pcie
> > > *imx6_pcie) {
> > > -	struct device *dev = imx6_pcie->pci->dev;
> > > -
> > >  	switch (imx6_pcie->drvdata->variant) {
> > >  	case IMX7D:
> > >  	case IMX8MQ:
> > > @@ -400,14 +398,6 @@ static void imx6_pcie_assert_core_reset(struct
> > imx6_pcie *imx6_pcie)
> > >  				   IMX6Q_GPR1_PCIE_REF_CLK_EN, 0 << 16);
> > >  		break;
> > >  	}
> > > -
> > > -	if (imx6_pcie->vpcie && regulator_is_enabled(imx6_pcie->vpcie) > 0) {
> > > -		int ret = regulator_disable(imx6_pcie->vpcie);
> > > -
> > > -		if (ret)
> > > -			dev_err(dev, "failed to disable vpcie regulator: %d\n",
> > > -				ret);
> > > -	}
> >
> > This commit is not just cleaning up the regulator usage as you state
> > in the commit message, this is removing the vpcie regulator_disable
> > from imx6_pcie_assert_core_reset().
> >
> > I would not do it, this is called for example on the shutdown callback
> > where it makes sense.
> Hi Francesco:
> Thanks for your review.
> Do you means that we should keep regulator_disable() here?
> Okay, I would change it later.
Hi Francesco:
One more complementary that we can't disable this regulator here, because
 that the regulator might not be enabled at all.

But in the case of suspend/resume operations, the regulator_disable() should
 be invoked behind of imx6_pcie_assert_core_reset () in resume callback to
 balance the enable/disable usage counter.
I would add this change later.
Thanks again for your review comments.

Best Regards
Richard
> 
> Best Regards
> Richard Zhu
> 
> >
> > Francesco