linux-kernel - Re: [PATCH V5 09/11] scsi: ufs: qcom : Refactor phy_power

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Message-ID: <5584c019-d435-4d1b-b38c-80fb9b9f00f6@quicinc.com>
Date: Thu, 22 May 2025 03:10:48 +0530
From: Nitin Rawat <quic_nitirawa@...cinc.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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 09/11] scsi: ufs: qcom : Refactor phy_power_on/off
 calls



On 5/21/2025 7:27 PM, Manivannan Sadhasivam wrote:
> On Thu, May 15, 2025 at 09:57:20PM +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

Sure, will address in next patchset.

> 
>> 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 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.
>>
> 
> This patch is not calling phy_calibrate().

updated commit text to remove phy_Calibrate from commit text

> 
>> 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 | 61 ++++++++++++++++++-------------------
>>   1 file changed, 29 insertions(+), 32 deletions(-)
>>
> 
> [...]
> 
>>   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;
>>   
>>   	/*
>>   	 * In case ufs_qcom_init() is not yet done, simply ignore.
>> @@ -1157,10 +1141,22 @@ 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);
>> +			if (err) {
>> +				dev_err(hba->dev, "phy power off failed, ret=%d\n", err);
>> +				return err;
>> +			}
>>   		}
>>   		break;
>>   	case POST_CHANGE:
>>   		if (on) {
>> +			err = phy_power_on(phy);
>> +			if (err) {
>> +				dev_err(hba->dev, "phy power on failed, ret = %d\n", err);
>> +				return err;
>> +			}
>> +
>>   			/* enable the device ref clock for HS mode*/
>>   			if (ufshcd_is_hs_mode(&hba->pwr_info))
>>   				ufs_qcom_dev_ref_clk_ctrl(host, true);
>> @@ -1343,9 +1339,10 @@ 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(host->generic_phy);
>> +	phy_power_off(phy);
> 
> This change is not at all needed.

In the current code, PHY resources (clocks and rails) remain active even 
when the link is in a hibernate state and all controller clocks are off. 
This results in a significant power penalty and can prevent CX power 
collapse.

These rails and clocks are only turned off when a system suspend is 
triggered, and even then, only at SPM level 5 where the link is turned 
off. This approach is not power-efficient.

As part of this series, the code that enables/disables the PHY's 
regulators and clocks is now confined to the phy_power_on and 
phy_power_off calls, with the rest moved to the calibration phase.

Therefore, we are invoking the phy_power_off and phy_power_on calls from 
ufs_qcom_setup_clocks, ensuring that the PHY's regulators and clocks can 
be turned on/off along with the UFS clocks, thereby achieving power savings.

Therefore, this patch is the cornerstone of this series.

Regards,
Nitin


> 
> - Mani
>