linux-kernel - Re: [PATCH] usb: dwc3: xilinx: improve error handling for PM APIs

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Message-ID: <20231205022430.rpdpgk4les7psp52@synopsys.com>
Date:   Tue, 5 Dec 2023 02:24:39 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "Mehta, Piyush" <piyush.mehta@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Simek, Michal" <michal.simek@....com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "git (AMD-Xilinx)" <git@....com>
Subject: Re: [PATCH] usb: dwc3: xilinx: improve error handling for PM APIs

Sorry for the delay response.

On Tue, Nov 14, 2023, Pandey, Radhey Shyam wrote:
> > -----Original Message-----
> > From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
> > Sent: Saturday, November 11, 2023 5:09 AM
> > To: Mehta, Piyush <piyush.mehta@....com>
> > Cc: gregkh@...uxfoundation.org; Simek, Michal <michal.simek@....com>;
> > Thinh Nguyen <Thinh.Nguyen@...opsys.com>; linux-usb@...r.kernel.org;
> > linux-kernel@...r.kernel.org; git (AMD-Xilinx) <git@....com>
> > Subject: Re: [PATCH] usb: dwc3: xilinx: improve error handling for PM APIs
> > 
> > On Wed, Nov 08, 2023, Piyush Mehta wrote:
> > > Improve error handling for PM APIs in the dwc3_xlnx_probe function by
> > > introducing devm_pm_runtime_enable and error label. Removed
> > > unnecessary API pm_runtime_disable call in dwc3_xlnx_remove.
> > >
> > > Signed-off-by: Piyush Mehta <piyush.mehta@....com>
> > > ---
> > >  drivers/usb/dwc3/dwc3-xilinx.c | 10 +++++++---
> > >  1 file changed, 7 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/usb/dwc3/dwc3-xilinx.c
> > > b/drivers/usb/dwc3/dwc3-xilinx.c index 5b7e92f476de..9cf26e9a1c3d
> > > 100644
> > > --- a/drivers/usb/dwc3/dwc3-xilinx.c
> > > +++ b/drivers/usb/dwc3/dwc3-xilinx.c
> > > @@ -294,10 +294,15 @@ static int dwc3_xlnx_probe(struct
> > > platform_device *pdev)
> > >
> > >  	pm_runtime_set_active(dev);
> > >  	pm_runtime_enable(dev);
> > > +	ret = devm_pm_runtime_enable(dev);
> > 
> > You just did pm_runtime_enable() right above, why
> > devm_pm_runtime_enable() again?
> 
> This will fix in next version.
> > 
> > > +	if (ret < 0)
> > > +		goto err_pm_set_suspended;
> > > +
> > >  	pm_suspend_ignore_children(dev, false);
> > > -	pm_runtime_get_sync(dev);
> > > +	return pm_runtime_resume_and_get(dev);
> > >
> > > -	return 0;
> > > +err_pm_set_suspended:
> > > +	pm_runtime_set_suspended(dev);
> > 
> > This doesn't look right. why set status suspended here?
> 
> Status is set to suspended in the exit path to undo the state
> set by pm_runtime_set_active(). The initial runtime PM status of 
> all devices is 'suspended'.
> 
> There is a mention of in Documentation/power/runtime_pm.rst
> For this reason, once pm_runtime_set_active() has been called for the device, 
> pm_runtime_enable() should be called for it too as soon as reasonably possible 
> or its run-time PM status should be changed back to 'suspended' with the help of
> pm_runtime_set_suspended().
> 

If your intention of treating the status of devm_pm_runtime_enable() as
the status of pm_runtime_enable(), then that's not correct.

BR,
Thinh