linux-kernel - RE: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage

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Date:   Thu, 9 Jun 2022 06:17:34 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Lucas Stach <l.stach@...gutronix.de>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "francesco.dolcini@...adex.com" <francesco.dolcini@...adex.com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...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>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage

> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: 2022年6月8日 15:27
> To: Hongxing Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> robh+dt@...nel.org; broonie@...nel.org; lorenzo.pieralisi@....com;
> jingoohan1@...il.com; festevam@...il.com;
> francesco.dolcini@...adex.com
> Cc: linux-pci@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; kernel@...gutronix.de; dl-linux-imx
> <linux-imx@....com>
> Subject: Re: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage
> 
> Am Freitag, dem 06.05.2022 um 09:47 +0800 schrieb Richard Zhu:
> > The driver should undo any enables it did itself. The regulator
> > disable shouldn't be basing decisions on regulator_is_enabled().
> >
> > To keep the balance of the regulator usage counter, disable the
> > regulator just behind of imx6_pcie_assert_core_reset() in resume and
> shutdown.
> >
> > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 19 +++++++------------
> >  1 file changed, 7 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index 7005a7910003..3ce3993d5797 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);
> > -	}
> >  }
> >
> >  static unsigned int imx6_pcie_grp_offset(const struct imx6_pcie
> > *imx6_pcie) @@ -580,7 +570,7 @@ static int
> imx6_pcie_deassert_core_reset(struct imx6_pcie *imx6_pcie)
> >  	struct device *dev = pci->dev;
> >  	int ret, err;
> >
> > -	if (imx6_pcie->vpcie && !regulator_is_enabled(imx6_pcie->vpcie)) {
> > +	if (imx6_pcie->vpcie) {
> >  		ret = regulator_enable(imx6_pcie->vpcie);
> >  		if (ret) {
> >  			dev_err(dev, "failed to enable vpcie regulator: %d\n", @@
> -653,7
> > +643,7 @@ static int imx6_pcie_deassert_core_reset(struct imx6_pcie
> *imx6_pcie)
> >  	return 0;
> >
> >  err_clks:
> > -	if (imx6_pcie->vpcie && regulator_is_enabled(imx6_pcie->vpcie) > 0) {
> > +	if (imx6_pcie->vpcie) {
> >  		ret = regulator_disable(imx6_pcie->vpcie);
> >  		if (ret)
> >  			dev_err(dev, "failed to disable vpcie regulator: %d\n", @@
> -1026,6
> > +1016,9 @@ static int imx6_pcie_resume_noirq(struct device *dev)
> >  		return 0;
> >
> >  	imx6_pcie_assert_core_reset(imx6_pcie);
> > +	if (imx6_pcie->vpcie)
> > +		regulator_disable(imx6_pcie->vpcie);
> > +
> This one looks misplaced. Surely you want the regulator to be on when
> resuming the PCIe subsystem. Isn't this just papering over a wrong usage count
> here, because there is no regulator_disable in imx6_pcie_suspend_noirq,
> where I would expect this to happen?
> 
Hi Lucas:
Thanks for your comments.
There was one regulator_disable() operation at the end of the
 imx6_pcie_assert_core_reset() function before.
When create the 5/8 patch, I follow the same behavior to disable the
regulator just behind the imx6_pcie_assert_core_reset() function.

Yes, it is. Imx6_pcie_suspend_noirq doesn't have the regulator_disable.
The regulaor_enable is contained in imx6_pcie_deassert_core_reset().
Both of the regulator_disable and regulator_enabe are invoked once in
 imx6_pcie_resume_noirq.
So, the regulator is on and has a balanced usage count after resume.
Best Regards
Richard Zhu

> Regards,
> Lucas
> 
> >  	imx6_pcie_init_phy(imx6_pcie);
> >  	imx6_pcie_deassert_core_reset(imx6_pcie);
> >  	dw_pcie_setup_rc(pp);
> > @@ -1259,6 +1252,8 @@ static void imx6_pcie_shutdown(struct
> > platform_device *pdev)
> >
> >  	/* bring down link, so bootloader gets clean state in case of reboot */
> >  	imx6_pcie_assert_core_reset(imx6_pcie);
> > +	if (imx6_pcie->vpcie)
> > +		regulator_disable(imx6_pcie->vpcie);
> >  }
> >
> >  static const struct imx6_pcie_drvdata drvdata[] = {
>