Re: [PATCH V2 6/6] scsi: ufs: host : Introduce phy_power_on/off wrapper function

[Nitin Rawat]

On 3/19/2025 1:20 AM, Bjorn Andersson wrote:
> 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

Hi Bjorn,

Thanks for the review. There are scenarios where ufshcd_link_startup() 
can call ufshcd_vops_link_startup_notify() multiple times during 
retries. This leads to the PHY reference count increasing continuously, 
preventing proper re-initialization of the PHY.

Recently, this issue was addressed with patch 7bac65687510 ("scsi: ufs: 
qcom: Power off the PHY if it was already powered on in 
ufs_qcom_power_up_sequence()"). However, I still want to maintain a 
reference count (ref_cnt) to safeguard against similar conditions in the 
code. Additionally, this approach helps avoid unnecessary phy_power_on 
and phy_power_off calls. Please let me know your thoughts.

Regrads,
Nitin




> > Co-developed-by: Can Guo <quic_cang@xxxxxxxxxxx>
> > Signed-off-by: Can Guo <quic_cang@xxxxxxxxxxx>
> > Signed-off-by: Nitin Rawat <quic_nitirawa@xxxxxxxxxxx>
> > ---
> >   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