linux-kernel - Re: [PATCH v4 3/7] usb: dwc3: core: Don't touch resets and clocks

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Message-ID: <x45slyuz5bboqzqdyhgd22dx4vfsam6unvzymrmjvunef7cpfv@ixqrlvyzt4jp>
Date: Thu, 27 Feb 2025 18:07:36 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Bjorn Andersson <bjorn.andersson@....qualcomm.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Felipe Balbi <balbi@...nel.org>, Wesley Cheng <quic_wcheng@...cinc.com>, 
	Saravana Kannan <saravanak@...gle.com>, Thinh Nguyen <Thinh.Nguyen@...opsys.com>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Konrad Dybcio <konradybcio@...nel.org>, 
	Frank Li <Frank.li@....com>, linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 3/7] usb: dwc3: core: Don't touch resets and clocks

On Thu, Feb 27, 2025 at 09:55:29AM -0600, Bjorn Andersson wrote:
> On Thu, Feb 27, 2025 at 06:24:17AM +0200, Dmitry Baryshkov wrote:
> > On Wed, Feb 26, 2025 at 04:17:50PM -0800, Bjorn Andersson wrote:
> > > When the core is integrated with glue, it's reasonable to assume that
> > > the glue driver will have to touch the IP before/after the core takes
> > > the hardware out and into reset. As such the glue must own these
> > > resources and be allowed to turn them on/off outside the core's
> > > handling.
> > > 
> > > Allow the platform or glue layer to indicate if the core logic for
> > > clocks and resets should be skipped to deal with this.
> > > 
> > > Signed-off-by: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
> > > ---
> > >  drivers/usb/dwc3/core.c | 19 +++++++++++--------
> > >  drivers/usb/dwc3/glue.h |  1 +
> > >  2 files changed, 12 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > > index d9f0a6782d36..aecdde8dc999 100644
> > > --- a/drivers/usb/dwc3/core.c
> > > +++ b/drivers/usb/dwc3/core.c
> > > @@ -2328,6 +2330,7 @@ static int dwc3_probe(struct platform_device *pdev)
> > >  
> > >  	probe_data.dwc = dwc;
> > >  	probe_data.res = res;
> > > +	probe_data.ignore_clocks_and_resets = false;
> > 
> > Isn't it a default value?
> > 
> 
> I like the false because it's explicit, but I have no strong attachment
> to it.

I'm more biased to the 'make unusal cases stand out', which means the
defaults can go away to highlight non-default cases.

> 
> That said, it's not the default value, because probe_data isn't
> zero-initialized. That would however make sense to do, in order to avoid
> surprises in the future when probe_data grows.

:-)

> 
> Regards,
> Bjorn
> 
> > >  
> > >  	return dwc3_core_probe(&probe_data);
> > >  }
> > > diff --git a/drivers/usb/dwc3/glue.h b/drivers/usb/dwc3/glue.h
> > > index e73cfc466012..1ddb451bdbd0 100644
> > > --- a/drivers/usb/dwc3/glue.h
> > > +++ b/drivers/usb/dwc3/glue.h
> > > @@ -17,6 +17,7 @@
> > >  struct dwc3_probe_data {
> > >  	struct dwc3 *dwc;
> > >  	struct resource *res;
> > > +	bool ignore_clocks_and_resets;
> > >  };
> > >  
> > >  int dwc3_core_probe(const struct dwc3_probe_data *data);
> > > 
> > > -- 
> > > 2.45.2
> > > 
> > 
> > -- 
> > With best wishes
> > Dmitry

-- 
With best wishes
Dmitry