linux-kernel - Re: [PATCH v8 5/8] PCI: imx6: Refine the regulator usage

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Message-ID: <20220225094301.GA2171975@francesco-nb.int.toradex.com>
Date:   Fri, 25 Feb 2022 10:43:01 +0100
From:   Francesco Dolcini <francesco.dolcini@...adex.com>
To:     Richard Zhu <hongxing.zhu@....com>
Cc:     l.stach@...gutronix.de, bhelgaas@...gle.com, broonie@...nel.org,
        lorenzo.pieralisi@....com, jingoohan1@...il.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 v8 5/8] PCI: imx6: Refine the regulator usage

On Fri, Feb 25, 2022 at 11:44:24AM +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().
> 
> To keep the balance of the regulator usage counter, disable the regulator
> just behind of imx6_pcie_assert_core_reset() in resume and shutdown.

While this patch does not look wrong and improving the existing code, I
do have a couple of concern.

1. It's weird that regulator enable/disable are really non symmetric in
the code, enable is in imx6_pcie_deassert_core_reset(), while disable is
not in imx6_pcie_assert_core_reset() but spread around.

2. We are playing around with vpcie during regulator during
suspend/resume, why? We currently have issue with suspend/resume when a
PCIe switch is there, with the final effect of PCIe being not usable
afterward. I fear like this is related to our issue.

What about vpcie enable in probe, and vpcie disable in shutdown and
that's all? 

Francesco

> 
> Signed-off-by: Richard Zhu <hongxing.zhu@....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 0f1b8c873a4a..160a0bd02098 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
> @@ -369,8 +369,6 @@ static int imx6_pcie_attach_pd(struct device *dev)
>  
>  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:
> @@ -400,14 +398,6 @@ static void imx6_pcie_assert_core_reset(struct imx6_pcie *imx6_pcie)
>  				   IMX6Q_GPR1_PCIE_REF_CLK_EN, 0 << 16);
>  		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);
> -	}
>  }
>  
>  static unsigned int imx6_pcie_grp_offset(const struct imx6_pcie *imx6_pcie)
> @@ -584,7 +574,7 @@ 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",
> @@ -657,7 +647,7 @@ 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",
> @@ -1029,6 +1019,9 @@ static int imx6_pcie_resume_noirq(struct device *dev)
>  		return 0;
>  
>  	imx6_pcie_assert_core_reset(imx6_pcie);
> +	if (imx6_pcie->vpcie)
> +		regulator_disable(imx6_pcie->vpcie);
> +
>  	imx6_pcie_init_phy(imx6_pcie);
>  	imx6_pcie_deassert_core_reset(imx6_pcie);
>  	dw_pcie_setup_rc(pp);
> @@ -1262,6 +1255,8 @@ 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);
>  }
>  
>  static const struct imx6_pcie_drvdata drvdata[] = {
> -- 
> 2.25.1
>