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

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Date:   Tue, 14 Nov 2023 05:47:48 +0000
From:   "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        "Mehta, Piyush" <piyush.mehta@....com>
CC:     "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

> -----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().

> 
> BR,
> Thinh
> 
> >
> >  err_clk_put:
> >  	clk_bulk_disable_unprepare(priv_data->num_clocks, priv_data-
> >clks);
> > @@ -315,7 +320,6 @@ static void dwc3_xlnx_remove(struct
> platform_device *pdev)
> >  	clk_bulk_disable_unprepare(priv_data->num_clocks, priv_data-
> >clks);
> >  	priv_data->num_clocks = 0;
> >
> > -	pm_runtime_disable(dev);
> >  	pm_runtime_put_noidle(dev);
> >  	pm_runtime_set_suspended(dev);
> >  }
> > --
> > 2.25.1
> >