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

From: Hongxing Zhu
Date: Tue Jun 28 2022 - 23:57:14 EST

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In reply to: Bjorn Helgaas: "Re: [PATCH v13 10/15] PCI: imx6: Turn off regulator when system is in suspend mode"
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> -----Original Message-----
> From: Bjorn Helgaas <helgaas@xxxxxxxxxx>
> Sent: 2022年6月28日 23:51
> To: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> Cc: l.stach@xxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; robh+dt@xxxxxxxxxx;
> broonie@xxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; festevam@xxxxxxxxx;
> francesco.dolcini@xxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> 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@xxxxxxxxxx>
> > > Sent: 2022年6月28日 3:52
> > > To: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> > > Cc: l.stach@xxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx; robh+dt@xxxxxxxxxx;
> > > broonie@xxxxxxxxxx; lorenzo.pieralisi@xxxxxxx; festevam@xxxxxxxxx;
> > > francesco.dolcini@xxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > > kernel@xxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> > > 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@xxxxxxxxxx>
> > > > > Sent: 2022年6月24日 6:20
> > > > > To: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> > > > > Cc: l.stach@xxxxxxxxxxxxxx; bhelgaas@xxxxxxxxxx;
> > > > > robh+dt@xxxxxxxxxx; broonie@xxxxxxxxxx;
> > > > > lorenzo.pieralisi@xxxxxxx; festevam@xxxxxxxxx;
> > > > > francesco.dolcini@xxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx;
> > > > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > > > linux-kernel@xxxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx;
> > > > > dl-linux-imx <linux-imx@xxxxxxx>
> > > > > 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%2
> > > > > > F%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@xxxxxxx
> > > > > > Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> > > > > > Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > > > > > ---
> > > > > > 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.
>
Hi Bjorn:
Thanks a lot for your review.

> 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].)
Yes, it is . I notice the warning too in my local tests. I made a mistake that
I assumed the PHY should be powered on firstly, then be initialized.
Since it is bug fix, how about to issue another fix commit after this series?

>
> IMO the imx6_pcie_clk_enable() should not be hidden inside
> imx6_pcie_deassert_core_reset().
Okay, would move the imx6_pcie_clk_enable() from imx6_pcie_deassert_core_reset()
to imx6_pcie_host_init().
Since the 6/15 of v13 has already Lucas' reviewed-by tag.
Can I combine these changes with the creation of the imx6_pcie_host_exit() and
imx6_pcie_host_stop_link() into one patch?

>
> [1]
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kern
> el.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Ftorvalds%2Flinux.git%2Ftr
> ee%2Fdrivers%2Fphy%2Fphy-core.c%3Fid%3Dv5.19-rc1%23n233&data=
> 05%7C01%7Chongxing.zhu%40nxp.com%7C0e7ce8e53ee0478aabd508da591
> e06f7%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6379202827
> 66167735%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoi
> V2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdat
> a=BQQnn1ju47AGwfQW48%2Ba%2BnlLszha8P0QAynr4G3qeLM%3D&res
> erved=0
Thanks a lot for your kindly reminder.

Best Regards
Richard

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In reply to: Bjorn Helgaas: "Re: [PATCH v13 10/15] PCI: imx6: Turn off regulator when system is in suspend mode"
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