linux-kernel - Re: [PATCH v3 08/12] usb: dwc3: core: Expose core driver as library

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Message-ID: <3s77lvw4dp3cg2s6tqt63wuexft3pusfbg2ibteacnd5z2dolf@p7mb2j5j5jlz>
Date: Tue, 14 Jan 2025 16:55:59 -0600
From: Bjorn Andersson <andersson@...nel.org>
To: Frank Li <Frank.li@....com>
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>, 
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 08/12] usb: dwc3: core: Expose core driver as library

On Tue, Jan 14, 2025 at 02:43:59PM -0500, Frank Li wrote:
> On Mon, Jan 13, 2025 at 09:11:41PM -0800, Bjorn Andersson wrote:
> > The DWC3 IP block is handled by three distinct device drivers: XHCI,
> > DWC3 core and a platform specific (optional) DWC3 glue driver.
> >
> > This has resulted in, at least in the case of the Qualcomm glue, the
> > presence of a number of layering violations, where the glue code either
> > can't handle, or has to work around, the fact that core might not probe
> > deterministically.
> >
> > An example of this is that the suspend path should operate slightly
> > different depending on the device operating in host or peripheral mode,
> > and the only way to determine the operating state is to peek into the
> > core's drvdata.
> >
> > The Qualcomm glue driver is expected to make updates in the qscratch
> > register region (the "glue" region) during role switch events, but with
> > the glue and core split using the driver model, there is no reasonable
> > way to introduce listeners for mode changes.
> >
> > Split the dwc3 core platform_driver callbacks and their implementation
> > and export the implementation, to make it possible to deterministically
> > instantiate the dwc3 core as part of the dwc3 glue drivers and to
> > allow flattening of the DeviceTree representation.
> >
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
> > ---
> >  drivers/usb/dwc3/core.c | 149 ++++++++++++++++++++++++++++++------------------
> >  drivers/usb/dwc3/glue.h |  22 +++++++
> >  2 files changed, 117 insertions(+), 54 deletions(-)
> >
> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> > index c22b8678e02e..930d812a9fbb 100644
> > --- a/drivers/usb/dwc3/core.c
> > +++ b/drivers/usb/dwc3/core.c
> > @@ -36,6 +36,7 @@
> >
> >  #include "core.h"
> >  #include "gadget.h"
> > +#include "glue.h"
> >  #include "io.h"
> >
> >  #include "debug.h"
> > @@ -2129,27 +2130,14 @@ static int dwc3_get_num_ports(struct dwc3 *dwc)
> >  	return 0;
> >  }
> >
> > -static int dwc3_probe(struct platform_device *pdev)
> > +int dwc3_init(struct dwc3 *dwc, struct resource *res)
> 
> Maybe need data struct, which included res. It may need pass down more
> information in future.
> 

Per this series we're resolving the race conditions stemming from
dwc3-qcom and core having different lifetimes, but more importantly it
will allow us to propose a mechanism for invoking role-switch events in
the glue code from the core - i.e. we are planning to add at least one
more argument here; so this proposal makes sense.

> >  {
> > -	struct device		*dev = &pdev->dev;
> > -	struct resource		*res, dwc_res;
> > +	struct device		*dev = dwc->dev;
> > +	struct resource		dwc_res;
> >  	unsigned int		hw_mode;
> >  	void __iomem		*regs;
> > -	struct dwc3		*dwc;
> >  	int			ret;
> >
> ...
> 
> > +++ b/drivers/usb/dwc3/glue.h
> > @@ -0,0 +1,22 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * glue.h - DesignWare USB3 DRD glue header
> > + */
> > +
> > +#ifndef __DRIVERS_USB_DWC3_GLUE_H
> > +#define __DRIVERS_USB_DWC3_GLUE_H
> > +
> > +#include <linux/types.h>
> > +#include "core.h"
> > +
> > +int dwc3_init(struct dwc3 *dwc, struct resource *res);
> > +void dwc3_uninit(struct dwc3 *dwc);
> > +
> > +int dwc3_runtime_suspend(struct dwc3 *dwc);
> > +int dwc3_runtime_resume(struct dwc3 *dwc);
> > +int dwc3_runtime_idle(struct dwc3 *dwc);
> > +int dwc3_suspend(struct dwc3 *dwc);
> > +int dwc3_resume(struct dwc3 *dwc);
> > +void dwc3_complete(struct dwc3 *dwc);
> 
> dwc3_usb_*()? There may be name polution in future. There are many IPs
> created by dwc.
> 

I thought dwc3 was uniquely associated with USB, but I don't have any
objections to your proposal.

Thanks,
Bjorn

> Frank
> 
> > +
> > +#endif
> >
> > --
> > 2.45.2
> >