linux-kernel - Re: [PATCH v3 4/8] usb: cdns3-ti: support reset-on-resume behavior

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Date: Mon, 26 Feb 2024 11:13:36 +0100
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: "Sergei Shtylyov" <sergei.shtylyov@...il.com>, "Greg Kroah-Hartman"
 <gregkh@...uxfoundation.org>, "Rob Herring" <robh+dt@...nel.org>,
 "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>, "Conor Dooley"
 <conor+dt@...nel.org>, "Roger Quadros" <rogerq@...nel.org>, "Peter Chen"
 <peter.chen@...nel.org>, "Pawel Laszczak" <pawell@...ence.com>, "Nishanth
 Menon" <nm@...com>, "Vignesh Raghavendra" <vigneshr@...com>, "Tero Kristo"
 <kristo@...nel.org>
Cc: "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
 Grégory Clement <gregory.clement@...tlin.com>, "Kevin
 Hilman" <khilman@...nel.org>, "Alan Stern" <stern@...land.harvard.edu>,
 <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 4/8] usb: cdns3-ti: support reset-on-resume behavior

Hello Sergey,

On Sat Feb 24, 2024 at 10:08 AM CET, Sergei Shtylyov wrote:
> On 2/23/24 7:05 PM, Théo Lebrun wrote:
> > Add match data support, with one boolean to indicate whether the
> > hardware resets after a system-wide suspend. If hardware resets, we
> > force execute ->runtime_resume() at system-wide resume to run the
> > hardware init sequence.
> > 
> > No compatible exploits this functionality, just yet.
> > 
> > Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> > ---
> >  drivers/usb/cdns3/cdns3-ti.c | 27 +++++++++++++++++++++++++++
> >  1 file changed, 27 insertions(+)
> > 
> > diff --git a/drivers/usb/cdns3/cdns3-ti.c b/drivers/usb/cdns3/cdns3-ti.c
> > index 4c8a557e6a6f..f76327566798 100644
> > --- a/drivers/usb/cdns3/cdns3-ti.c
> > +++ b/drivers/usb/cdns3/cdns3-ti.c
> [...]
> > @@ -220,8 +226,29 @@ static int cdns_ti_runtime_resume(struct device *dev)
> >  	return 0;
> >  }
> >  
> > +static int cdns_ti_suspend(struct device *dev)
> > +{
> > +	struct cdns_ti *data = dev_get_drvdata(dev);
> > +
> > +	if (data->match_data && data->match_data->reset_on_resume)
> > +		return pm_runtime_force_suspend(dev);
> > +	else
>
>    Pointless *else* after *return*...

Indeed! I used this form explicitely as it reads nicely: "if reset on
reset, force suspend, else do nothing". It also prevents the error of
adding behavior below the if-statement without seeing that it won't
apply to both cases.

If you do believe it would make the code better I'll happily change it
for the next revision, I do not mind.

Thanks for the review Sergey!

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com