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, 22 Aug 2013 15:41:30 -0500
From:	Felipe Balbi <balbi@...com>
To:	Kumar Gala <galak@...eaurora.org>
CC:	"Ivan T. Ivanov" <iivanov@...sol.com>,
	Pawel Moll <pawel.moll@....com>, "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 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 :-)

-- 
balbi

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