linux-kernel - RE: [PATCH v13 10/15] PCI: imx6: Turn off regulator when system is in suspend mode

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Message-ID: <AS8PR04MB86765811BC787E18FF6BD8C58CB89@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date:   Tue, 28 Jun 2022 03:48:01 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     "l.stach@...gutronix.de" <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>,
        "festevam@...il.com" <festevam@...il.com>,
        "francesco.dolcini@...adex.com" <francesco.dolcini@...adex.com>,
        "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 v13 10/15] PCI: imx6: Turn off regulator when system is in
 suspend mode

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: 2022年6月28日 3:52
> To: Hongxing Zhu <hongxing.zhu@....com>
> Cc: l.stach@...gutronix.de; bhelgaas@...gle.com; robh+dt@...nel.org;
> broonie@...nel.org; lorenzo.pieralisi@....com; festevam@...il.com;
> francesco.dolcini@...adex.com; 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 v13 10/15] PCI: imx6: Turn off regulator when system is in
> suspend mode
> 
> On Fri, Jun 24, 2022 at 05:05:00AM +0000, Hongxing Zhu wrote:
> > > -----Original Message-----
> > > From: Bjorn Helgaas <helgaas@...nel.org>
> > > Sent: 2022年6月24日 6:20
> > > To: Hongxing Zhu <hongxing.zhu@....com>
> > > Cc: l.stach@...gutronix.de; bhelgaas@...gle.com; robh+dt@...nel.org;
> > > broonie@...nel.org; lorenzo.pieralisi@....com; festevam@...il.com;
> > > francesco.dolcini@...adex.com; 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 v13 10/15] PCI: imx6: Turn off regulator when
> > > system is in suspend mode
> > >
> > > On Fri, Jun 17, 2022 at 06:31:09PM +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().
> > > >
> > > > Move the regulator_disable to the suspend function, turn off
> > > > regulator when the system is in suspend mode.
> > > >
> > > > To keep the balance of the regulator usage counter, disable the
> > > > regulator in shutdown.
> > > >
> > > > Link:
> > > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > lore
> > > > .kernel.org%2Fr%2F1655189942-12678-6-git-send-email-hongxing.z&am
> p
> > > > ;d
> > > at
> > > >
> > >
> a=05%7C01%7Chongxing.zhu%40nxp.com%7C5633fa1bf3c443e203e108da55
> > > 667dc2%
> > > >
> > >
> 7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6379161959277276
> > > 04%7CUnkn
> > > >
> > >
> own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1
> > > haWwi
> > > >
> > >
> LCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=1Kbzn3XSVvt3gGPrEy%2
> > > BET8EZn4I
> > > > dwS%2BhUZ3AalZ2YZ0%3D&amp;reserved=0
> > > > hu@....com
> > > > Signed-off-by: Richard Zhu <hongxing.zhu@....com>
> > > > Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.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 2b42c37f1617..f72eb609769b 100644
> > > > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > > > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > > > @@ -670,8 +670,6 @@ static void imx6_pcie_clk_disable(struct
> > > > imx6_pcie
> > > > *imx6_pcie)
> > > >
> > > >  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:
> > > > @@ -702,14 +700,6 @@ static void
> > > > imx6_pcie_assert_core_reset(struct
> > > imx6_pcie *imx6_pcie)
> > > >  		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);
> > > > -	}
> > > > -
> > > >  	/* Some boards don't have PCIe reset GPIO. */
> > > >  	if (gpio_is_valid(imx6_pcie->reset_gpio))
> > > >  		gpio_set_value_cansleep(imx6_pcie->reset_gpio,
> > > > @@ -722,7 +712,7 @@ static int
> > > > imx6_pcie_deassert_core_reset(struct
> > > imx6_pcie *imx6_pcie)
> > > >  	struct device *dev = pci->dev;
> > > >  	int ret;
> > > >
> > > > -	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", @@
> > > -795,7
> > > > +785,7 @@ 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", @@
> > > -1022,6
> > > > +1012,9 @@ static int imx6_pcie_suspend_noirq(struct device *dev)
> > > >  		break;
> > > >  	}
> > > >
> > > > +	if (imx6_pcie->vpcie)
> > > > +		regulator_disable(imx6_pcie->vpcie);
> > > > +
> > > >  	return 0;
> > > >  }
> > >
> > > The suspend and resume methods should be symmetric, and they should
> > > *look* symmetric.
> > >
> > > imx6_pcie_suspend_noirq() disables the regulator, so
> > > imx6_pcie_resume_noirq() should enable it.
> > >
> > > imx6_pcie_suspend_noirq() calls imx6_pcie_clk_disable() to disable
> > > several clocks.  imx6_pcie_resume_noirq() should call
> > > imx6_pcie_clk_enable() to enable them.
> > >
> > > imx6_pcie_clk_enable() *is* called in the resume path, but it's
> > > buried inside imx6_pcie_host_init() and
> > > imx6_pcie_deassert_core_reset().  That makes it hard to analyze.
> > >
> > > We should be able to look at imx6_pcie_suspend_noirq() and
> > > imx6_pcie_resume_noirq() and easily see that the resume path resumes
> > > everything that was suspended in the suspend path.
> >
> > Yes, it is. It's better to keep suspend/resume symmetric as much as
> > possible.  In resume, the host_init is invoked, clocks, regulators and
> > so on would be initialized properly.
> >
> > Unfortunately, there is no according host_exit() that can be called to
> > do the reversed clocks, regulators disable operations in the suspend.
> > So, the clocks and regulator disable are explicitly invoked in suspend
> > callback.
> >
> > How about to do the incremental updates if the .host_exit can be added
> > later?
> 
> This doesn't seem very convincing because everything here is in the
> imx6 domain.  The only DWC core thing here is the dw_pcie_setup_rc() called
> in imx6_pcie_resume_noirq(), and it doesn't call back to any
> imx6 code.
> 
> So you should be able to make an imx6_pcie_host_exit() or whatever that
> corresponds to imx6_pcie_host_init().
Hi Bjorn:
Thanks for your kindly help to review it. That's reasonable.

So, to make it symmetric with imx6_pcie_host_init() and imx6_pcie_start_link().
The according local functions imx6_pcie_host_exit() and imx6_pcie_stop_link()
would be created.

BTW, to be symmetric with imx6_pcie_host_init(), the parameter of
imx6_pcie_host_exit() is same to the parameter of imx6_pcie_host_init().
So do imx6_pcie_stop_link() and imx6_pcie_start_link().
Are you satisfied with the following functions?

static void imx6_pcie_stop_link(struct dw_pcie *pci)
{
        struct device *dev = pci->dev;

        /* Turn off PCIe LTSSM */
        imx6_pcie_ltssm_disable(dev);
}

static void imx6_pcie_host_exit(struct pcie_port *pp)
{
        struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
        struct imx6_pcie *imx6_pcie = to_imx6_pcie(pci);

        imx6_pcie_clk_disable(imx6_pcie);
        if (imx6_pcie->phy) {
                if (phy_power_off(imx6_pcie->phy))
                        dev_err(pci->dev, "unable to power off PHY\n");
                phy_exit(imx6_pcie->phy);
        }

        if (imx6_pcie->vpcie)
                regulator_disable(imx6_pcie->vpcie);
}

Best Regards
Richard Zhu