linux-kernel - Re: [PATCH 3/9] PCI: imx6: Simplify reset handling by using by using *_FLAG_HAS_*

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Date:   Wed, 06 Dec 2023 17:52:23 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Frank Li <Frank.Li@....com>, imx@...ts.linux.dev,
        Richard Zhu <hongxing.zhu@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        "open list:PCI DRIVER FOR IMX6" <linux-pci@...r.kernel.org>,
        "moderated list:PCI DRIVER FOR IMX6" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/9] PCI: imx6: Simplify reset handling by using by
 using *_FLAG_HAS_*_RESET

Hi Frank,

On Mi, 2023-12-06 at 10:58 -0500, Frank Li wrote:
> Refactors the reset handling logic in the imx6 PCI driver by adding
> IMX6_PCIE_FLAG_HAS_*_RESET bitmask define for drvdata::flags.
> 
> The drvdata::flags and a bitmask ensures a cleaner and more scalable
> switch-case structure for handling reset.
> 
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
>  drivers/pci/controller/dwc/pci-imx6.c | 115 +++++++++++---------------
>  1 file changed, 47 insertions(+), 68 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> index bcf52aa86462..62d77fabd82a 100644
> --- a/drivers/pci/controller/dwc/pci-imx6.c
> +++ b/drivers/pci/controller/dwc/pci-imx6.c
[...]
> @@ -696,18 +698,13 @@ static void imx6_pcie_clk_disable(struct imx6_pcie *imx6_pcie)
>  
>  static void imx6_pcie_assert_core_reset(struct imx6_pcie *imx6_pcie)
>  {
> -	switch (imx6_pcie->drvdata->variant) {
> -	case IMX7D:
> -	case IMX8MQ:
> -	case IMX8MQ_EP:
> +	if (imx6_check_flag(imx6_pcie, IMX6_PCIE_FLAG_HAS_PHY_RESET))

This check is not strictly necessary. If the flag is not set,
imx6_pcie->pciephy_reset is guaranteed to be NULL, and then
reset_control_assert() is a no-op. Same for the other (de)assert
calls below.

[...]

> @@ -1335,36 +1319,24 @@ static int imx6_pcie_probe(struct platform_device *pdev)
>  					     "failed to get pcie phy\n");
>  	}
>  
> -	switch (imx6_pcie->drvdata->variant) {
> -	case IMX7D:
> -		if (dbi_base->start == IMX8MQ_PCIE2_BASE_ADDR)
> -			imx6_pcie->controller_id = 1;
> -
> -		imx6_pcie->pciephy_reset = devm_reset_control_get_exclusive(dev,
> -									    "pciephy");
> -		if (IS_ERR(imx6_pcie->pciephy_reset)) {
> -			dev_err(dev, "Failed to get PCIEPHY reset control\n");
> -			return PTR_ERR(imx6_pcie->pciephy_reset);
> -		}
> -
> -		imx6_pcie->apps_reset = devm_reset_control_get_exclusive(dev,
> -									 "apps");
> -		if (IS_ERR(imx6_pcie->apps_reset)) {
> -			dev_err(dev, "Failed to get PCIE APPS reset control\n");
> -			return PTR_ERR(imx6_pcie->apps_reset);
> -		}
> -		break;
> -	case IMX8MM:
> -	case IMX8MM_EP:
> -	case IMX8MP:
> -	case IMX8MP_EP:
> -		imx6_pcie->apps_reset = devm_reset_control_get_exclusive(dev,
> -									 "apps");
> +	if (imx6_check_flag(imx6_pcie, IMX6_PCIE_FLAG_HAS_APP_RESET)) {
> +		imx6_pcie->apps_reset = devm_reset_control_get_exclusive(dev, "apps");
[...]

I wonder whether we should just defer the check whether apps/pciephy
resets should be used to the device tree validation, and make this an
unconditional call to get an optional reset control:

	imx6_pcie->apps_reset = devm_reset_control_get_optional_exclusive(dev, "apps");

regards
Philipp