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Message-ID: <k37lk3poz6kzrgnby4sikwmz6rg4ysxsticn3opcil4j3njylp@cvmgwiw6nwy5>
Date: Wed, 21 May 2025 15:01:53 +0100
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Nitin Rawat <quic_nitirawa@...cinc.com>
Cc: vkoul@...nel.org, kishon@...nel.org,
James.Bottomley@...senpartnership.com, martin.petersen@...cle.com, bvanassche@....org,
andersson@...nel.org, neil.armstrong@...aro.org, dmitry.baryshkov@....qualcomm.com,
konrad.dybcio@....qualcomm.com, quic_rdwivedi@...cinc.com, quic_cang@...cinc.com,
linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-scsi@...r.kernel.org
Subject: Re: [PATCH V5 10/11] scsi: ufs: qcom : Introduce phy_power_on/off
wrapper function
On Thu, May 15, 2025 at 09:57:21PM +0530, Nitin Rawat wrote:
Subject should mention ufs_qcom_phy_power_{on/off} as phy_power_{on/off} are
generic APIs.
> There can be scenarios where phy_power_on is called when PHY is
> already on (phy_count=1). For instance, ufs_qcom_power_up_sequence
> can be called multiple times from ufshcd_link_startup as part of
> ufshcd_hba_enable call for each link startup retries(max retries =3),
> causing the PHY reference count to increase and leading to inconsistent
> phy behavior.
>
> Similarly, there can be scenarios where phy_power_on or phy_power_off
> might be called directly from the UFS controller driver when the PHY
> is already powered on or off respectiely, causing similar issues.
>
> To fix this, introduce ufs_qcom_phy_power_on and ufs_qcom_phy_power_off
> wrappers for phy_power_on and phy_power_off. These wrappers will use an
> is_phy_pwr_on flag to check if the PHY is already powered on or off,
> avoiding redundant calls. Protect the is_phy_pwr_on flag with a mutex
> to ensure safe usage and prevent race conditions.
>
This smells like the phy_power_{on/off} calls are not balanced and you are
trying to workaround that in the UFS driver.
- Mani
> 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 3ee4ab90dfba..583db910efd4 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -479,6 +479,38 @@ 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);
> @@ -507,7 +539,7 @@ 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);
> }
>
> @@ -524,7 +556,7 @@ 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);
> @@ -1121,7 +1153,6 @@ 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;
>
> /*
> @@ -1142,7 +1173,7 @@ static int ufs_qcom_setup_clocks(struct ufs_hba *hba, bool on,
> 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;
> @@ -1151,7 +1182,7 @@ 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;
> @@ -1339,10 +1370,9 @@ 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 0a5cfc2dd4f7..f51b774e17be 100644
> --- a/drivers/ufs/host/ufs-qcom.h
> +++ b/drivers/ufs/host/ufs-qcom.h
> @@ -281,6 +281,10 @@ 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
>
--
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