RE: [PATCH v12 09/13] PCI: imx6: Turn off regulator when system is in suspend mode

From: Hongxing Zhu <hongxing.zhu@nxp.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Lucas Stach <l.stach@pengutronix.de>,
	Rob Herring <robh+dt@kernel.org>, Mark Brown <broonie@kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Fabio Estevam <festevam@gmail.com>,
	Francesco Dolcini <francesco.dolcini@toradex.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	dl-linux-imx <linux-imx@nxp.com>,
	Bjorn Helgaas <bhelgaas@google.com>
Subject: RE: [PATCH v12 09/13] PCI: imx6: Turn off regulator when system is in suspend mode
Date: Fri, 17 Jun 2022 05:57:38 +0000	[thread overview]
Message-ID: <AS8PR04MB8676CC46A0DBFD5E18A613638CAF9@AS8PR04MB8676.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20220616155619.GA1089749@bhelgaas>

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@kernel.org>
> Sent: 2022年6月16日 23:56
> To: Hongxing Zhu <hongxing.zhu@nxp.com>
> Cc: Lucas Stach <l.stach@pengutronix.de>; Rob Herring <robh+dt@kernel.org>;
> Mark Brown <broonie@kernel.org>; Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.com>; Fabio Estevam <festevam@gmail.com>;
> Francesco Dolcini <francesco.dolcini@toradex.com>; 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>; Bjorn Helgaas
> <bhelgaas@google.com>
> Subject: Re: [PATCH v12 09/13] PCI: imx6: Turn off regulator when system is in
> suspend mode
> 
> On Thu, Jun 16, 2022 at 02:23:29AM +0000, Hongxing Zhu wrote:
> > > -----Original Message-----
> > > From: Bjorn Helgaas <helgaas@kernel.org>
> > > Sent: 2022年6月16日 7:31
> > > To: Hongxing Zhu <hongxing.zhu@nxp.com>; Lucas Stach
> > > <l.stach@pengutronix.de>; Rob Herring <robh+dt@kernel.org>; Mark
> > > Brown <broonie@kernel.org>; Lorenzo Pieralisi
> > > <lorenzo.pieralisi@arm.com>; Fabio Estevam <festevam@gmail.com>;
> > > Francesco Dolcini <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>; Bjorn Helgaas <bhelgaas@google.com>
> > > Subject: Re: [PATCH v12 09/13] PCI: imx6: Turn off regulator when
> > > system is in suspend mode
> > >
> > > On Wed, Jun 15, 2022 at 06:15:47PM -0500, Bjorn Helgaas wrote:
> > > > From: Richard Zhu <hongxing.zhu@nxp.com>
> > > >
> > > > 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%7C8dea46d908d34cb4825808da4
> > > f270eaf%
> > > >
> > >
> 7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6379093264156415
> > > 35%7CUnkn
> > > >
> > >
> own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1
> > > haWwi
> > > >
> > >
> LCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=tqzlcCmtSkUNxNzJ0Fr5o
> > > CR3X2CTH
> > > > 4dwUJS4NXt5KRc%3D&amp;reserved=0
> > > > hu@nxp.com
> > > > Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
> > > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.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 6eddd0b5f628..537b8a2e0e3b 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, 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", @@
> > > -796,7
> > > > +786,7 @@ 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", @@
> > > -1023,6
> > > > +1013,9 @@ static int imx6_pcie_suspend_noirq(struct device *dev)
> > > >  		break;
> > > >  	}
> > > >
> > > > +	if (imx6_pcie->vpcie)
> > > > +		regulator_disable(imx6_pcie->vpcie);
> > >
> > > This is a little bit ugly because imx6_pcie_suspend_noirq() and
> > > imx6_pcie_resume_noirq() are not symmetric.
> > >
> > > We call regulator_disable() directly here in
> > > imx6_pcie_suspend_noirq(), but the corresponding regulator_enable() is
> buried in imx6_pcie_deassert_core_reset().
> > >
> > > It would be nicer if the suspend and resume paths looked more
> > > similar, as
> > > rockchip_pcie_suspend_noirq() and rockchip_pcie_resume_noirq() do,
> > > for example.
> > Yes, it is. The regulator_disable()/regulator_enable() are not invoked
> > symmetrically.
> >
> > In the original codes, the regulator_disable() is contained in
> > imx6_pcie_assert_core_reset() and with _eanbled() check.
> > And regulator_enable() is embedded in imx6_pcie_deassert_core_reset().
> > Both the regulator disable and enable are invoked in resume before.
> > I move the regulator_disable to suspend mode refer to Lucas' comments.
> >
> > Refer to the current situation, how about to move the
> > regulator_disable()  out of imx6_pcie_deassert_core_reset() too?
> 
> I think it's important to tweak this closer to the pattern of other drivers like
> exynos and rockchip.
> 
> exynos_pcie_resume_noirq() calls exynos_pcie_host_init().
> imx6_pcie_resume_noirq() is VERY similar to imx6_pcie_host_init(), and I think
> it should call imx6_pcie_host_init() instead of duplicating that code.  The only
> real difference is that imx6_pcie_host_init() calls imx6_setup_phy_mpll() while
> imx6_pcie_resume_noirq() does not.
> I suspect that's a bug.
> 
> I don't think "regulator_enable(imx6_pcie->vpcie)" really has anything to do
> with imx6_pcie_deassert_core_reset() and it should be moved out.
> The typical pattern is to enable regulators in *_probe() and
> *_resume_noirq() and disable them in *_remove() and *_suspend_noirq().
> I think you should do the same unless there's some reason you can't.
> 
> Can you give this a try, starting with this v12 posting?
Thanks a lot for your inspiration.
Exactly, these codes are almost same. The host_init can be invoked directly
 in resume. I would re-change the #12/13 of v12, and send the v13 later.

Best Regards
Richard Zhu

> 
> Bjorn