linux-kernel - Re: [PATCH V4 10/11] scsi: ufs: qcom : Introduce phy_power

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Message-ID: <be69cd1e-c04c-4976-9be1-390631316d3f@quicinc.com>
Date: Fri, 9 May 2025 17:19:16 +0530
From: Nitin Rawat <quic_nitirawa@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, <vkoul@...nel.org>,
        <kishon@...nel.org>, <manivannan.sadhasivam@...aro.org>,
        <James.Bottomley@...senPartnership.com>, <martin.petersen@...cle.com>,
        <bvanassche@....org>, <andersson@...nel.org>,
        <neil.armstrong@...aro.org>
CC: <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 V4 10/11] scsi: ufs: qcom : Introduce phy_power_on/off
 wrapper function

On 5/9/2025 5:07 PM, Konrad Dybcio wrote:
> On 5/3/25 6:24 PM, 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.
>>
>> 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>
>> ---
> 
> The PHY framework does the same thing internally already, this seems
> unnecessary

Hi Konrad,

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.

Regards,
Nitin

> 
> Konrad