linux-kernel - Re: [PATCH v1 2/2] PCI: dwc: histb: Simplify reset control handling by using reset_control

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Message-ID: <20250826162545.GA838376@bhelgaas>
Date: Tue, 26 Aug 2025 11:25:45 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Anand Moon <linux.amoon@...il.com>
Cc: Shawn Guo <shawn.guo@...aro.org>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	"open list:PCIE DRIVER FOR HISILICON STB" <linux-pci@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 2/2] PCI: dwc: histb: Simplify reset control handling
 by using reset_control_bulk*() function

In subject, remove "dwc: " to follow historical convention.

On Tue, Aug 26, 2025 at 05:12:41PM +0530, Anand Moon wrote:
> Currently, the driver acquires and asserts/deasserts the resets
> individually thereby making the driver complex to read.
> 
> This can be simplified by using the reset_control_bulk() APIs.
> 
> Use devm_reset_control_bulk_get_exclusive() API to acquire all the resets
> and use reset_control_bulk_{assert/deassert}() APIs to assert/deassert them
> in bulk.

Please include a note that this changes the order of reset assert and
deassert and explain why this is safe.

> Signed-off-by: Anand Moon <linux.amoon@...il.com>
> ---
>  drivers/pci/controller/dwc/pcie-histb.c | 57 ++++++++++++-------------
>  1 file changed, 28 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-histb.c b/drivers/pci/controller/dwc/pcie-histb.c
> index 4022349e85d2..4ba5c9af63a0 100644
> --- a/drivers/pci/controller/dwc/pcie-histb.c
> +++ b/drivers/pci/controller/dwc/pcie-histb.c
> @@ -49,14 +49,20 @@
>  #define PCIE_LTSSM_STATE_MASK		GENMASK(5, 0)
>  #define PCIE_LTSSM_STATE_ACTIVE		0x11
>  
> +#define PCIE_HISTB_NUM_RESETS   ARRAY_SIZE(histb_pci_rsts)
> +
> +static const char * const histb_pci_rsts[] = {
> +	"soft",
> +	"sys",
> +	"bus",
> +};
> +
>  struct histb_pcie {
>  	struct dw_pcie *pci;
>  	struct  clk_bulk_data *clks;
>  	int     num_clks;
>  	struct phy *phy;
> -	struct reset_control *soft_reset;
> -	struct reset_control *sys_reset;
> -	struct reset_control *bus_reset;
> +	struct  reset_control_bulk_data reset[PCIE_HISTB_NUM_RESETS];
>  	void __iomem *ctrl;
>  	struct gpio_desc *reset_gpio;
>  	struct regulator *vpcie;
> @@ -198,9 +204,8 @@ static const struct dw_pcie_host_ops histb_pcie_host_ops = {
>  
>  static void histb_pcie_host_disable(struct histb_pcie *hipcie)
>  {
> -	reset_control_assert(hipcie->soft_reset);
> -	reset_control_assert(hipcie->sys_reset);
> -	reset_control_assert(hipcie->bus_reset);
> +	reset_control_bulk_assert(PCIE_HISTB_NUM_RESETS,
> +				  hipcie->reset);
>  
>  	clk_bulk_disable_unprepare(hipcie->num_clks, hipcie->clks);
>  
> @@ -236,14 +241,19 @@ static int histb_pcie_host_enable(struct dw_pcie_rp *pp)
>  		goto reg_dis;
>  	}
>  
> -	reset_control_assert(hipcie->soft_reset);
> -	reset_control_deassert(hipcie->soft_reset);
> -
> -	reset_control_assert(hipcie->sys_reset);
> -	reset_control_deassert(hipcie->sys_reset);
> +	ret = reset_control_bulk_assert(PCIE_HISTB_NUM_RESETS,
> +					hipcie->reset);
> +	if (ret) {
> +		dev_err(dev, "Couldn't assert reset %d\n", ret);
> +		goto reg_dis;
> +	}
>  
> -	reset_control_assert(hipcie->bus_reset);
> -	reset_control_deassert(hipcie->bus_reset);
> +	ret = reset_control_bulk_deassert(PCIE_HISTB_NUM_RESETS,
> +					  hipcie->reset);
> +	if (ret) {
> +		dev_err(dev, "Couldn't dessert reset %d\n", ret);

s/dessert/deassert/

> +		goto reg_dis;
> +	}
>  
>  	return 0;
>  
> @@ -321,23 +331,12 @@ static int histb_pcie_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, hipcie->num_clks,
>  				     "failed to get clocks\n");
>  
> -	hipcie->soft_reset = devm_reset_control_get(dev, "soft");
> -	if (IS_ERR(hipcie->soft_reset)) {
> -		dev_err(dev, "couldn't get soft reset\n");
> -		return PTR_ERR(hipcie->soft_reset);
> -	}
> +	ret = devm_reset_control_bulk_get_exclusive(dev,
> +						    PCIE_HISTB_NUM_RESETS,
> +						    hipcie->reset);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Cannot get the Core resets\n");
>  
> -	hipcie->sys_reset = devm_reset_control_get(dev, "sys");
> -	if (IS_ERR(hipcie->sys_reset)) {
> -		dev_err(dev, "couldn't get sys reset\n");
> -		return PTR_ERR(hipcie->sys_reset);
> -	}
> -
> -	hipcie->bus_reset = devm_reset_control_get(dev, "bus");
> -	if (IS_ERR(hipcie->bus_reset)) {
> -		dev_err(dev, "couldn't get bus reset\n");
> -		return PTR_ERR(hipcie->bus_reset);
> -	}
>  
>  	hipcie->phy = devm_phy_get(dev, "phy");
>  	if (IS_ERR(hipcie->phy)) {
> -- 
> 2.50.1
>