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

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Message-ID: <b3a9e4aa400cc03bcdc0e8d5dcd4ae82cacada86.camel@pengutronix.de>
Date: Tue, 26 Aug 2025 14:46:00 +0200
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Anand Moon <linux.amoon@...il.com>, 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>, "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

On Di, 2025-08-26 at 17:12 +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.
> 
> 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",
> +};
> +
[...]
> @@ -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,

Note that this changes the order of assertion/deassertion, not only
because resets lines are now switched in bulk, but also because
reset_control_bulk_deassert() deasserts the reset lines in reverse
order. So this does

If the three resets are independent and order doesn't matter,

Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp