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Date: Thu, 09 Jun 2022 09:47:18 +0200
From: Lucas Stach <l.stach@...gutronix.de>
To: Hongxing Zhu <hongxing.zhu@....com>,
"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
Am Donnerstag, dem 09.06.2022 um 06:17 +0000 schrieb Hongxing Zhu:
> > -----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.
>
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.
Regards,
Lucas
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