linux-kernel - Re: [PATCH v4 11/13] phy: qcom: qmp-usbc: Add USB/DP mutex handling

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Message-ID: <nfugwwknnlxls75yo5rex6ggu5nzpq6enyx6e6nfnfei3icxjg@t7dnzcfcjw4o>
Date: Fri, 12 Sep 2025 13:32:28 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Xiangxu Yin <xiangxu.yin@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        fange.zhang@....qualcomm.com, yongxing.mou@....qualcomm.com,
        li.liu@....qualcomm.com, tingwei.zhang@....qualcomm.com,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH v4 11/13] phy: qcom: qmp-usbc: Add USB/DP mutex handling

On Thu, Sep 11, 2025 at 10:55:08PM +0800, Xiangxu Yin wrote:
> Introduce mutual exclusion between USB and DP PHY modes to prevent
> simultaneous activation.

Describe the problem that you are trying to solve first.

> 
> Signed-off-by: Xiangxu Yin <xiangxu.yin@....qualcomm.com>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-usbc.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c b/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c
> index 613239d15a6a3bba47a647db4e663713f127c93e..866277036089c588cf0c63204efb91bbec5430ae 100644
> --- a/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c
> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-usbc.c
> @@ -1061,6 +1061,19 @@ static int qmp_usbc_usb_power_off(struct phy *phy)
>  	return 0;
>  }
>  
> +static int qmp_check_mutex_phy(struct qmp_usbc *qmp, bool is_dp)

mutex has a very well defined use case - a sleeping lock. Please find
some ofther name.

> +{
> +	if ((is_dp && qmp->usb_init_count) ||
> +	    (!is_dp && qmp->dp_init_count)) {
> +		dev_err(qmp->dev,
> +			"PHY is configured for %s, can not enable %s\n",
> +			is_dp ? "USB" : "DP", is_dp ? "DP" : "USB");
> +		return -EBUSY;
> +	}
> +
> +	return 0;
> +}
> +
>  static int qmp_usbc_usb_enable(struct phy *phy)
>  {
>  	struct qmp_usbc *qmp = phy_get_drvdata(phy);

-- 
With best wishes
Dmitry