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

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Message-ID: <1377090364.15070.13.camel@iivanov-dev.int.mm-sol.com>
Date:	Wed, 21 Aug 2013 16:06:04 +0300
From:	"Ivan T. Ivanov" <iivanov@...sol.com>
To:	Pawel Moll <pawel.moll@....com>
Cc:	Kumar Gala <galak@...eaurora.org>, "balbi@...com" <balbi@...com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Mark Rutland <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>,
	Paul Zimmerman <paul.zimmerman@...opsys.com>
Subject: Re: [PATCH v4 2/3] usb: phy: Add Qualcomm SS-USB and HS-USB drivers
 for DWC3 core

On Tue, 2013-08-20 at 18:01 +0100, Pawel Moll wrote: 
> On Tue, 2013-08-20 at 16:06 +0100, Pawel Moll wrote:
> > On Tue, 2013-08-20 at 16:01 +0100, 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:
> > > >>> Hi,
> > > >>> 
> > > >>> On Tue, 2013-08-20 at 08:37 -0500, Felipe Balbi wrote: 
> > > >>>> Hi,
> > > >>>> 
> > > >>>> On Tue, Aug 20, 2013 at 04:32:23PM +0300, Ivan T. Ivanov wrote:
> > > >>>>>> On Tue, Aug 20, 2013 at 12:56:04PM +0300, Ivan T. Ivanov wrote:
> > > >>>>>>> From: "Ivan T. Ivanov" <iivanov@...sol.com>
> > > >>>>>>> 
> > > >>>>>>> These drivers handles control and configuration of the HS
> > > >>>>>>> and SS USB PHY transceivers. They are part of the driver
> > > >>>>>>> which manage Synopsys DesignWare USB3 controller stack
> > > >>>>>>> inside Qualcomm SoC's.
> > > >>>>>>> 
> > > >>>>>>> Signed-off-by: Ivan T. Ivanov <iivanov@...sol.com>
> > > >>>>>>> ---
> > > >>>>>>> drivers/usb/phy/Kconfig           |   11 ++
> > > >>>>>>> drivers/usb/phy/Makefile          |    2 +
> > > >>>>>>> drivers/usb/phy/phy-msm-dwc3-hs.c |  327 ++++++++++++++++++++++++++++++++
> > > >>>>>>> drivers/usb/phy/phy-msm-dwc3-ss.c |  374 +++++++++++++++++++++++++++++++++++++
> > > >>>>>> 
> > > >>>>>> please rename these PHY drivers, they have nothing to do with DWC3. PHYs
> > > >>>>>> don't care about the USB controller.
> > > >>>>> 
> > > >>>>> 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?
> > 
> > I afraid the answer may be: "it depends on the SOC". In my past I had to
> > initialize a (SATA) PHY by implementing a software JTAG state machine,
> > as the PHY's registers were not memory mapped *at all*. And the IP
> > itself came from Synopsys, Cadence or yet another EDA company...
> 
> Having said all that... If the PHY's spec at least defined layout of the
> registers in question and driver was using regmap API to talk to the
> device (initially regmap-mmio), it has some chances to become universal.
> The SOCs designed like "my" one would have to provide a custom regmap
> implementation.

Sound reasonable. Unfortunately I don't have PHY's IP spec. 

Regards,
Ivan

> 
> Paweł
> 


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