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

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Date:   Thu, 23 Jun 2022 17:19:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Richard 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, 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://lore.kernel.org/r/1655189942-12678-6-git-send-email-hongxing.z
> 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.

Bjorn