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:	Thu, 29 Aug 2013 20:28:40 +0300
From:	"Ivan T. Ivanov" <iivanov@...sol.com>
To:	balbi@...com
Cc:	Kumar Gala <galak@...eaurora.org>, Pawel Moll <pawel.moll@....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 Thu, 2013-08-22 at 15:41 -0500, Felipe Balbi wrote:
> On Wed, Aug 21, 2013 at 10:13:28AM -0500, Kumar Gala wrote:
> > 
> > On Aug 21, 2013, at 8:06 AM, Ivan T. Ivanov wrote:
> > 
> > > 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. 
> > 
> > Looking into this it appears that the register wrapper around the IP
> > is most likely highly specific to qualcomm as I'm not seeing a
> > register interface around the DWC HS PHY.
> 
> Then it's set, we'll go with this driver :-)
> 

Does this mean that driver could be merged? 

Regards,
Ivan


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