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

[Hongxing Zhu <hongxing.zhu@nxp.com>]

> -----Original Message-----
> From: Lucas Stach <l.stach@pengutronix.de>
> Sent: 2022年6月9日 15:47
> To: Hongxing Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com;
> robh+dt@kernel.org; broonie@kernel.org; lorenzo.pieralisi@arm.com;
> jingoohan1@gmail.com; festevam@gmail.com;
> francesco.dolcini@toradex.com
> Cc: linux-pci@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> linux-kernel@vger.kernel.org; kernel@pengutronix.de; dl-linux-imx
> <linux-imx@nxp.com>
> Subject: Re: [PATCH v9 5/8] PCI: imx6: Refine the regulator usage
> 
> Am Donnerstag, dem 09.06.2022 um 06:17 +0000 schrieb Hongxing Zhu:
> > > -----Original Message-----
> > > From: Lucas Stach <l.stach@pengutronix.de>
> > > Sent: 2022年6月8日 15:27
> > > To: Hongxing Zhu <hongxing.zhu@nxp.com>; bhelgaas@google.com;
> > > robh+dt@kernel.org; broonie@kernel.org; lorenzo.pieralisi@arm.com;
> > > jingoohan1@gmail.com; festevam@gmail.com;
> > > francesco.dolcini@toradex.com
> > > Cc: linux-pci@vger.kernel.org;
> > > linux-arm-kernel@lists.infradead.org;
> > > linux-kernel@vger.kernel.org; kernel@pengutronix.de; dl-linux-imx
> > > <linux-imx@nxp.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@nxp.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.
> >
> 
> Yea, my argument is that when we are moving around the regulator handling
> anyways, we should move the regulator_disable into the suspend function. It's
> the right thing to do: we don't want the bus to be powered when the system is
> in suspend and while the use-count is correct, it's confusing to read the resume
> function otherwise.
> 
Thanks for your quick reply.
Understand. I would move the regulator_disable at the end of the suspend
 function if you're fine with it.

Best Regards
Richard Zhu

> Regards,
> Lucas