linux-kernel - Re: [PATCH v4 2/3] usb: phy: Add Qualcomm SS-USB and HS-USB drivers for DWC3 core

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Date:	Tue, 27 Aug 2013 14:58:59 -0500
From:	Felipe Balbi <balbi@...com>
To:	Paul Zimmerman <Paul.Zimmerman@...opsys.com>
CC:	"Ivan T. Ivanov" <iivanov@...sol.com>,
	Kumar Gala <galak@...eaurora.org>,
	"balbi@...com" <balbi@...com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"ian.campbell@...rix.com" <ian.campbell@...rix.com>,
	"rob@...dley.net" <rob@...dley.net>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"idos@...eaurora.org" <idos@...eaurora.org>,
	"mgautam@...eaurora.org" <mgautam@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"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>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] usb: phy: Add Qualcomm SS-USB and HS-USB drivers
 for DWC3 core

Hi,

On Thu, Aug 22, 2013 at 09:24:49PM +0000, Paul Zimmerman wrote:
> > From: Ivan T. Ivanov [mailto:iivanov@...sol.com]
> > Sent: Tuesday, August 20, 2013 8:26 AM
> > 
> > On Tue, 2013-08-20 at 10:01 -0500, Kumar Gala wrote:
> > > On Aug 20, 2013, at 9:54 AM, Ivan T. Ivanov wrote:
> > >
> > > >
> > > > Hi,
> > > >
> > > > On Tue, 2013-08-20 at 09:33 -0500, Felipe Balbi wrote:
> > > >> On Tue, Aug 20, 2013 at 05:09:11PM +0300, Ivan T. Ivanov wrote:
> > > >>>
> > > >>> On Tue, 2013-08-20 at 08:37 -0500, Felipe Balbi wrote:
> > > >>>>
> > > >>>> On Tue, Aug 20, 2013 at 04:32:23PM +0300, Ivan T. Ivanov wrote:
> > > >>>>>
> > > >>>>> I think they are SNPS DesignWare PHY's, additionally
> > > >>>>> wrapped with Qualcomm logic. I could substitute "dwc3"
> > > >>>>> with just "dw", which will be more correct.
> > > >>>>
> > > >>>> alright, thank you. Let's add Paul to the loop since he might have very
> > > >>>> good insight in the synopsys PHYs.
> > > >>>>
> > > >>>> mental note: if any other platform shows up with Synopsys PHY, ask them
> > > >>>> to use this driver instead :-)
> > > >>>
> > > >>> I really doubt that this will bi possible. Control of the PHY's is
> > > >>> not directly trough ULPI, UTMI or PIPE3 interfaces, but trough
> > > >>> QSCRATCH registers, which of course is highly Qualcomm specific.
> > > >>
> > > >> isn't it a memory mapped IP ? doesn't synopsys provide their own set of
> > > >> registers ?
> > > >
> > > > From what I see it is not directly mapped. How QSCRATCH write and
> > > > reads transactions are translated to DW IP is unclear to me.
> > >
> > >
> > > I think the question is how does SW access them?
> > 
> > "USB QSCRATCH Hardware registers" don't ask me what is this :-)
> > or like Pawel says: "it depends on the SOC" .
> 
> To answer the question "doesn't synopsys provide their own set of
> registers", we provide registers in our USB cores to access the PHYs
> through I2C, ULPI/UTMI, or PIPE3 interfaces. But if someone wants to use
> our PHY with some other controller that doesn't provide that, then they
> may need to implement their own register set, as Qualcomm has apparently
> done.

thanks for clarifying. that pretty much hinders writing any sort of
generic drivers for Synopsys' PHYs though :-s

But I guess that's alright.

-- 
balbi

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