linux-kernel - Re: [PATCH V2 6/6] scsi: ufs: host : Introduce phy_power

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Message-ID: <jx6t2745x3swbfiqwsii5xdumhpanc435ooucrg2nlyl22llho@epleg24suedr>
Date: Tue, 18 Mar 2025 14:50:21 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Nitin Rawat <quic_nitirawa@...cinc.com>
Cc: vkoul@...nel.org, kishon@...nel.org, manivannan.sadhasivam@...aro.org, 
	James.Bottomley@...senpartnership.com, martin.petersen@...cle.com, konrad.dybcio@....qualcomm.com, 
	quic_rdwivedi@...cinc.com, linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org, Can Guo <quic_cang@...cinc.com>
Subject: Re: [PATCH V2 6/6] scsi: ufs: host : Introduce phy_power_on/off
 wrapper function

On Tue, Mar 18, 2025 at 08:19:44PM +0530, Nitin Rawat wrote:
> Introduce ufs_qcom_phy_power_on and ufs_qcom_phy_power_off wrapper
> functions with mutex protection to ensure safe usage of is_phy_pwr_on
> and prevent possible race conditions.
> 

Please describe the problem properly here. Are you introducing the mutex
because there is a problem, or because you want to be "safe"?

Why is it "refcounted", is the calling code paths no longer in sync? How
long has the current implementation been broken?

Regards,
Bjorn

> Co-developed-by: Can Guo <quic_cang@...cinc.com>
> Signed-off-by: Can Guo <quic_cang@...cinc.com>
> Signed-off-by: Nitin Rawat <quic_nitirawa@...cinc.com>
> ---
>  drivers/ufs/host/ufs-qcom.c | 44 +++++++++++++++++++++++++++++++------
>  drivers/ufs/host/ufs-qcom.h |  4 ++++
>  2 files changed, 41 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index 5c7b6c75d669..8f80724e64b9 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -421,6 +421,38 @@ static u32 ufs_qcom_get_hs_gear(struct ufs_hba *hba)
>  	return UFS_HS_G3;
>  }
> 
> +static int ufs_qcom_phy_power_on(struct ufs_hba *hba)
> +{
> +	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> +	struct phy *phy = host->generic_phy;
> +	int ret = 0;
> +
> +	guard(mutex)(&host->phy_mutex);
> +	if (!host->is_phy_pwr_on) {
> +		ret = phy_power_on(phy);
> +		if (!ret)
> +			host->is_phy_pwr_on = true;
> +	}
> +
> +	return ret;
> +}
> +
> +static int ufs_qcom_phy_power_off(struct ufs_hba *hba)
> +{
> +	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> +	struct phy *phy = host->generic_phy;
> +	int ret = 0;
> +
> +	guard(mutex)(&host->phy_mutex);
> +	if (host->is_phy_pwr_on) {
> +		ret = phy_power_off(phy);
> +		if (!ret)
> +			host->is_phy_pwr_on = false;
> +	}
> +
> +	return ret;
> +}
> +
>  static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
>  {
>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> @@ -449,7 +481,7 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
>  		return ret;
> 
>  	if (phy->power_count) {
> -		phy_power_off(phy);
> +		ufs_qcom_phy_power_off(hba);
>  		phy_exit(phy);
>  	}
> 
> @@ -466,7 +498,7 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
>  		goto out_disable_phy;
> 
>  	/* power on phy - start serdes and phy's power and clocks */
> -	ret = phy_power_on(phy);
> +	ret = ufs_qcom_phy_power_on(hba);
>  	if (ret) {
>  		dev_err(hba->dev, "%s: phy power on failed, ret = %d\n",
>  			__func__, ret);
> @@ -1017,7 +1049,6 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
>  				 enum ufs_notify_change_status status)
>  {
>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> -	struct phy *phy = host->generic_phy;
>  	int err;
> 
>  	/*
> @@ -1037,7 +1068,7 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
>  				/* disable device ref_clk */
>  				ufs_qcom_dev_ref_clk_ctrl(host, false);
>  			}
> -			err = phy_power_off(phy);
> +			err = ufs_qcom_phy_power_off(hba);
>  			if (err) {
>  				dev_err(hba->dev, "phy power off failed, ret=%d\n", err);
>  					return err;
> @@ -1046,7 +1077,7 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
>  		break;
>  	case POST_CHANGE:
>  		if (on) {
> -			err = phy_power_on(phy);
> +			err = ufs_qcom_phy_power_on(hba);
>  			if (err) {
>  				dev_err(hba->dev, "phy power on failed, ret = %d\n", err);
>  				return err;
> @@ -1233,10 +1264,9 @@ static int ufs_qcom_init(struct ufs_hba *hba)
>  static void ufs_qcom_exit(struct ufs_hba *hba)
>  {
>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> -	struct phy *phy = host->generic_phy;
> 
>  	ufs_qcom_disable_lane_clks(host);
> -	phy_power_off(phy);
> +	ufs_qcom_phy_power_off(hba);
>  	phy_exit(host->generic_phy);
>  }
> 
> diff --git a/drivers/ufs/host/ufs-qcom.h b/drivers/ufs/host/ufs-qcom.h
> index d0e6ec9128e7..3db29fbcd40b 100644
> --- a/drivers/ufs/host/ufs-qcom.h
> +++ b/drivers/ufs/host/ufs-qcom.h
> @@ -252,6 +252,10 @@ struct ufs_qcom_host {
>  	u32 phy_gear;
> 
>  	bool esi_enabled;
> +	/* flag to check if phy is powered on */
> +	bool is_phy_pwr_on;
> +	/* Protect the usage of is_phy_pwr_on against racing */
> +	struct mutex phy_mutex;
>  };
> 
>  struct ufs_qcom_drvdata {
> --
> 2.48.1
> 
>