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

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Date:   Mon, 27 Jun 2022 14:51:32 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Hongxing Zhu <hongxing.zhu@....com>
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

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%2Flore
> > > .kernel.org%2Fr%2F1655189942-12678-6-git-send-email-hongxing.z&amp;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().