linux-kernel - Re: [PATCH 3/5] PCI: qcom: Keep PERST# GPIO state as-is during probe

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Message-ID: <be6aecbc-3ea4-4282-b777-0dc8ae1b8c26@oss.qualcomm.com>
Date: Fri, 9 Jan 2026 12:14:05 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
        Vinod Koul <vkoul@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jingoo Han <jingoohan1@...il.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kwilczynski@...nel.org>,
        Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 3/5] PCI: qcom: Keep PERST# GPIO state as-is during probe

On 1/9/26 8:21 AM, Krishna Chaitanya Chundru wrote:
> The PERST# signal is used to reset PCIe devices. Currently, the driver
> requests the GPIO with GPIOD_OUT_HIGH, which forces the line high
> during probe. This can unintentionally assert reset early, breaking

                                         ^ de-assert, probably?

Konrad

> link retention or causing unexpected device behavior.
> 
> Change the request to use GPIOD_ASIS so the driver preserves the
> existing state configured by the bootloader or firmware. This allows
> platforms that manage PERST# externally to maintain proper reset
> sequencing.
> 
> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 7b92e7a1c0d9364a9cefe1450818f9cbfc7fd3ac..9342f9c75f1c3017b55614069a7aa821a6fb8da7 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1711,7 +1711,7 @@ static int qcom_pcie_parse_port(struct qcom_pcie *pcie, struct device_node *node
>  	int ret;
>  
>  	reset = devm_fwnode_gpiod_get(dev, of_fwnode_handle(node),
> -				      "reset", GPIOD_OUT_HIGH, "PERST#");
> +				      "reset", GPIOD_ASIS, "PERST#");
>  	if (IS_ERR(reset))
>  		return PTR_ERR(reset);
>  
> @@ -1772,7 +1772,7 @@ static int qcom_pcie_parse_legacy_binding(struct qcom_pcie *pcie)
>  	if (IS_ERR(phy))
>  		return PTR_ERR(phy);
>  
> -	reset = devm_gpiod_get_optional(dev, "perst", GPIOD_OUT_HIGH);
> +	reset = devm_gpiod_get_optional(dev, "perst", GPIOD_ASIS);
>  	if (IS_ERR(reset))
>  		return PTR_ERR(reset);
>  
>