linux-kernel - RE: [PATCH 2/3] drivers: usb: dwc3: Add adjust_frame_length

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Date:	Mon, 27 Jul 2015 06:56:48 +0000
From:	Badola Nikhil <nikhil.badola@...escale.com>
To:	"balbi@...com" <balbi@...com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: RE: [PATCH 2/3] drivers: usb: dwc3: Add adjust_frame_length_quirk

> -----Original Message-----
> From: Felipe Balbi [mailto:balbi@...com]
> Sent: Thursday, July 23, 2015 8:39 PM
> To: Felipe Balbi
> Cc: Badola Nikhil-B46172; linux-kernel@...r.kernel.org; linux-
> usb@...r.kernel.org; linux-omap@...r.kernel.org;
> gregkh@...uxfoundation.org
> Subject: Re: [PATCH 2/3] drivers: usb: dwc3: Add adjust_frame_length_quirk
> 
> Hi again,
> 
> On Thu, Jul 23, 2015 at 09:55:32AM -0500, Felipe Balbi wrote:
> > > diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h index
> > > 0447788..b7a5119 100644
> > > --- a/drivers/usb/dwc3/core.h
> > > +++ b/drivers/usb/dwc3/core.h
> > > @@ -124,6 +124,7 @@
> > >  #define DWC3_GEVNTCOUNT(n)	(0xc40c + (n * 0x10))
> > >
> > >  #define DWC3_GHWPARAMS8		0xc600
> > > +#define DWC3_GFLADJ		0xc630
> > >
> > >  /* Device Registers */
> > >  #define DWC3_DCFG		0xc700
> > > @@ -234,6 +235,10 @@
> > >  /* Global HWPARAMS6 Register */
> > >  #define DWC3_GHWPARAMS6_EN_FPGA			(1 << 7)
> > >
> > > +/* Global Frame Length Adjustment Register */
> > > +#define GFLADJ_30MHZ_REG_SEL		(1 << 7)
> >
> > always prepend with DWC3_ like *all* other macros in this file.
> >
> > Also, match docs to ease grepping. This should be called
> > DWC3_GFLADJ_30MHZ_SDBND_SEL

GFLADJ_30MHZ_REG_SEL is the field's name in LS1021A Reference Manual as well 
as dwc3 databook. Though DWC3_GFLADJ_30MHZ_SDBND_SEL seems more
relevant. 

> 
> yet another problem is that this register doesn't exist in *all* versions of
> DWC3. It was introduced in version 2.50a so the branch I typed above needs
> one extra check, and since it's getting so large, it deserves be factored out
> into its own function.
> 
> static int dwc3_frame_length_adjustment(struct dwc3 *dwc, u32 fladj) {
> 	u32 reg;
> 	u32 dft;
> 
> 	if (dwc->revision <= DWC3_REVISION_250A)
> 		return 0;
> 
> 	if (fladj == 0)
> 		return 0;
> 
> 	reg = dwc3_readl(dwc->regs, DWC3_GFLADJ);
> 	dft = reg & 0x3f; /* needs a mask macro */
> 
> 	if (!dev_WARN_ONCE(dwc->dev, dft == fladj,
> 		"requested value same as default, ignoring\n")) {
> 		reg &= ~0x3f; /* needs a mask macro */
> 		reg |= DWC3_GFLADJ_30MHZ_SDBND_SEL |
> 			DWC3_GFLADJ_30MHZ(fladj_value);
> 
> 		dwc3_writel(dwc->regs, DWC3_GFLADJ, reg);
> 	}
> }
> 
> you really *MUST* check this sort of this out when writing patches. It's not
> only about *your* SoC. You gotta remember we have a ton of different
> users and those a prone to major grumpyness should a completely unrelated
> patch break their use case.
> 
> You have access to the IP's documentation, and that contains the entire
> history of the IP itself, so it's easy to figure all of this out with a simple search
> in the documentation.
> 
> One extra detail is that you were very careless when writing to the GFLADJ
> register too. You simply wrote your 30MHz sideband value, potentially
> clearing other bits which shouldn't be touched. That alone can add
> regressions.
> 
> When resending, make sure all 3 patches reach linux-usb. I still can't find
> patch 3/3.
>

Will take care of above scenarios and resend patches cc'ing linux-usb in each of them.

Regarding acceptance of the patch only when it's used in glue layer, there is no freescale's
glue layer present for dwc3 as of now. Furthermore, there is not any platform specific 
code required in glue layer apart from the ones present in dwc3/core.c. 

Please suggest.


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