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

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Message-ID: <6v2kyk3rhss4itvo4dhwxyf3mp7ey7gh5abaklgwa27b4fw6ce@ofyuo3ortl4p>
Date: Thu, 27 Feb 2025 09:55:29 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.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 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.

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