linux-kernel - Re: [PATCH V1 1/2] scsi: ufs: qcom : Refactor phy_power

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Date: Wed, 24 Jan 2024 13:52:31 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Nitin Rawat <quic_nitirawa@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Vinod Koul <vkoul@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	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>,
	Naveen Kumar Goud Arepalli <quic_narepall@...cinc.com>
Subject: Re: [PATCH V1 1/2] scsi: ufs: qcom : Refactor phy_power_on/off calls

On Fri, Jan 12, 2024 at 09:03:47PM +0530, Nitin Rawat wrote:
> Commit 3f6d1767b1a0 ("phy: ufs-qcom: Refactor all init steps into
> phy_poweron") removes the phy_power_on/off from ufs_qcom_setup_clocks

s/removes/moved

> to suspend/resume func.
> 
> To have a better power saving, remove the phy_power_on/off calls from
> resume/suspend path and put them back to ufs_qcom_setup_clocks, so that
> PHY's regulators & clks can be turned on/off along with UFS's clocks.
> 
> Since phy phy_power_on is separated out from phy calibrate, make
> separate calls to phy_power_on and phy_calibrate calls from ufs qcom
> driver.
> 

Above change should be in a separate patch.

> Also add a mutex lock to protect the usage of is_phy_pwr_on against
> possible racing.
> 
> Co-developed-by: Can Guo <quic_cang@...cinc.com>
> Signed-off-by: Can Guo <quic_cang@...cinc.com>
> Co-developed-by: Naveen Kumar Goud Arepalli <quic_narepall@...cinc.com>
> Signed-off-by: Naveen Kumar Goud Arepalli <quic_narepall@...cinc.com>
> Signed-off-by: Nitin Rawat <quic_nitirawa@...cinc.com>
> ---
>  drivers/ufs/host/ufs-qcom.c | 104 +++++++++++++++++++++++-------------
>  drivers/ufs/host/ufs-qcom.h |   4 ++
>  2 files changed, 72 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index 39eef470f8fa..2721a30f0db8 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -338,6 +338,46 @@ 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;
> +
> +	mutex_lock(&host->phy_mutex);

You do not need mutex to protect a variable. If you want to ensure that the
access to the flag is atomic, you can use test_and_{set/clear}_bit helpers.

> +	if (!host->is_phy_pwr_on) {
> +		ret = phy_power_on(phy);
> +		if (ret) {
> +			mutex_unlock(&host->phy_mutex);
> +			return ret;
> +		}
> +		host->is_phy_pwr_on = true;
> +	}
> +	mutex_unlock(&host->phy_mutex);
> +
> +	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;
> +
> +	mutex_lock(&host->phy_mutex);
> +	if (host->is_phy_pwr_on) {
> +		ret = phy_power_off(phy);
> +		if (ret) {
> +			mutex_unlock(&host->phy_mutex);
> +			return ret;
> +		}
> +		host->is_phy_pwr_on = false;
> +	}
> +	mutex_unlock(&host->phy_mutex);
> +
> +	return ret;
> +}
> +
>  static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
>  {
>  	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> @@ -378,13 +418,18 @@ 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);
>  		goto out_disable_phy;
>  	}
> 
> +	ret = phy_calibrate(phy);
> +	if (ret) {
> +		dev_err(hba->dev, "%s: Failed to calibrate PHY %d\n",
> +				  __func__, ret);

Even though the driver already has a lot of "__func__" to print the function
names in error log, please do not add more. I will get rid of the existing ones
at some point.

- Mani

-- 
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