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Date: Tue, 28 Jun 2022 10:51:08 -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 Tue, Jun 28, 2022 at 03:48:01AM +0000, Hongxing Zhu wrote:
> > -----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&sdata=1Kbzn3XSVvt3gGPrEy%2
> > > > BET8EZn4I
> > > > > dwS%2BhUZ3AalZ2YZ0%3D&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().
>
> 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);
> }
After the current series, imx6_pcie_host_init() looks like:
imx6_pcie_host_init
phy_power_on
regulator_enable
imx6_pcie_deassert_core_reset
imx6_pcie_clk_enable
phy_init
and you propose:
imx6_pcie_host_exit
imx6_pcie_clk_disable
phy_power_off
phy_exit
regulator_disable
Generally they should do things in the reverse order.
imx6_pcie_host_init() does phy_power_on(), regulator_enable(),
imx6_pcie_clk_enable().
imx6_pcie_host_exit() should do imx6_pcie_clk_disable(),
regulator_disable(), phy_power_off().
(It looks like imx6_pcie_host_init() calls phy_power_on() and
phy_init() in the wrong order [1].)
IMO the imx6_pcie_clk_enable() should not be hidden inside
imx6_pcie_deassert_core_reset().
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/phy/phy-core.c?id=v5.19-rc1#n233
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