linux-kernel - Re: [PATCH] phy: qualcomm: m31-eusb2: Add runtime pm ops

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Message-ID: <e4f33bf0-05d9-4aad-b00e-fb7cc2c2633b@oss.qualcomm.com>
Date: Mon, 27 Oct 2025 12:11:11 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Prashanth K <prashanth.k@....qualcomm.com>, Vinod Koul
 <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phy: qualcomm: m31-eusb2: Add runtime pm ops

On 10/27/25 12:09 PM, Prashanth K wrote:
> 
> 
> On 10/27/2025 1:55 PM, Konrad Dybcio wrote:
>> On 10/27/25 7:24 AM, Prashanth K wrote:
>>> Add runtime power management operation callbacks for M31 EUSB2 PHY.
>>> Enable/disable the clocks based on the runtime suspend/resume calls.
>>>
>>> Signed-off-by: Prashanth K <prashanth.k@....qualcomm.com>
>>> ---
>>
>> [...]
>>
>>>  static int m31eusb2_phy_probe(struct platform_device *pdev)
>>>  {
>>>  	struct phy_provider *phy_provider;
>>> @@ -270,6 +298,17 @@ static int m31eusb2_phy_probe(struct platform_device *pdev)
>>>  		return dev_err_probe(dev, PTR_ERR(phy->clk),
>>>  				     "failed to get clk\n");
>>>  
>>> +	dev_set_drvdata(dev, phy);
>>> +	pm_runtime_set_active(dev);
>>> +	pm_runtime_enable(dev);
>>> +
>>> +	/*
>>> +	 * Prevent runtime pm from being ON by default. Users can enable
>>> +	 * it using power/control in sysfs.
>>> +	 */
>>> +	pm_runtime_forbid(dev);
>>
>> This screams "this patch is broken" or "there are bad issues" which
>> you did not describe at all.
>>
>> Konrad
> 
> Hi Konrad, I was followed the same sequence from other phy drivers
> containing pm_ops. I assume the runtime_forbid is added to control
> runtime pm from userspace.

Other drivers call runtime_forbid() because the implementation doesn't
work.. Or at least historically the usb3 part hasn't been able to sus/
res properly

Konrad