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Message-ID: <AS8PR04MB8676238B47BA35890CC1F8B18C899@AS8PR04MB8676.eurprd04.prod.outlook.com>
Date:   Wed, 13 Jul 2022 12:55:14 +0000
From:   Hongxing Zhu <hongxing.zhu@....com>
To:     Lucas Stach <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>
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 v14 10/17] PCI: imx6: Turn off regulator when system is in
 suspend mode

> -----Original Message-----
> From: Lucas Stach <l.stach@...gutronix.de>
> Sent: 2022年7月13日 19:23
> To: Hongxing Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> robh+dt@...nel.org; broonie@...nel.org; lorenzo.pieralisi@....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 v14 10/17] PCI: imx6: Turn off regulator when system is in
> suspend mode
> 
> Am Mittwoch, dem 13.07.2022 um 10:56 +0000 schrieb Hongxing Zhu:
> > > -----Original Message-----
> > > From: Lucas Stach <l.stach@...gutronix.de>
> > > Sent: 2022年7月13日 16:34
> > > To: Hongxing Zhu <hongxing.zhu@....com>; bhelgaas@...gle.com;
> > > robh+dt@...nel.org; broonie@...nel.org; lorenzo.pieralisi@....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 v14 10/17] PCI: imx6: Turn off regulator when
> > > system is in suspend mode
> > >
> > > Am Freitag, dem 01.07.2022 um 11:25 +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().
> > > >
> > > > 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&amp;d
> > > at
> > > >
> > >
> a=05%7C01%7Chongxing.zhu%40nxp.com%7C361c9bf365b64895482808da6
> > > 4aa7cca%
> > > >
> > >
> 7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6379329806385373
> > > 39%7CUnkn
> > > >
> > >
> own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1
> > > haWwi
> > > >
> > >
> LCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=A%2Fw6AFCddC0T%2FA
> > > ocBT%2F7OJZ
> > > > ddAeYPTbgeAxpHpPubkw%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",
> > >
> > > The regulator really has nothing to do with the core reset. Please
> > > move this regulator enable into imx6_pcie_host_init().
> > Hi Lucas:
> > Thanks for your comments.
> > Got that. Had done it in the 11/17 commit.
> >
> > >
> > > > @@ -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;
> > > >  }
> > > >
> > > > @@ -1268,6 +1261,8 @@ static void imx6_pcie_shutdown(struct
> > > > platform_device *pdev)
> > > >
> > > >  	/* bring down link, so bootloader gets clean state in case of
> > > > reboot */
> > > >  	imx6_pcie_assert_core_reset(imx6_pcie);
> > > > +	if (imx6_pcie->vpcie)
> > > > +		regulator_disable(imx6_pcie->vpcie);
> > >
> > > This looks like a separate change, not mentioned in the commit
> > > message.
> > > I'm not sure if we should do this. Shutdown is supposed to just stop
> > > the device, which is already achieved by
> > > imx6_pcie_assert_core_reset().
> > >
> > > If we would want to do a full cleanup here we would also need to
> > > disable clocks and get the reset GPIO into asserted state. I don't
> > > think we want to do all of this here.
> > The regulator_disable() was contained in
> > imx6_pcie_assert_core_reset() before.
> > When refine the regulator usage, the regulator_disable() is moved out
> > of
> >  imx6_pcie_assert_core_reset().
> > Based on the discussion [1] with Francesco.
> > To keep the same behavior, the regulator_disable() is placed behind of
> >  imx6_pcie_assert_core_reset() in imx6_pcie_shutdown() here.
> > [1]
> > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatc
> >
> hwork.ozlabs.org%2Fproject%2Flinux-pci%2Fpatch%2F1644290735-3797-6-gi
> t
> >
> -send-email-hongxing.zhu%40nxp.com%2F&amp;data=05%7C01%7Chongxing.
> zhu%
> >
> 40nxp.com%7C88b4bedd17e84c440c5608da64c20698%7C686ea1d3bc2b4c6
> fa92cd99
> >
> c5c301635%7C0%7C0%7C637933081743458707%7CUnknown%7CTWFpbGZ
> sb3d8eyJWIjo
> >
> iMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C300
> 0%7C%
> >
> 7C%7C&amp;sdata=NHl4prCMrfR4KAZgIaCuJX%2FOrMJW3Up31NX%2FzMMY
> pag%3D&amp
> > ;reserved=0
> 
> I disagree with Francesco on this. This kind of half-done cleanup doesn't help
> in any way. Either we care about doing a full cleanup here, which would
> involve clocks and reset GPIOs, or we just care about getting the core in a state
> where it survives a reboot, which frankly was the original intention when I
> added the shutdown callback.
> 
> As the devices on the bus will see a full PERST reset via the reset GPIO anyways,
> there is no harm in keeping them powered across the reboot.
Okay, I see.
Thanks for your comment.
I can remove it if you insist.

Best Regards
Richard Zhu

> 
> Regards,
> Lucas

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