[PATCH] Documentation: dts: fsl-usb: Document USB node compatible string for IP version

[Ramneek Mehresh]

> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Wednesday, August 27, 2014 4:23 AM
> To: Mehresh Ramneek-B31383
> Cc: Badola Nikhil-B46172; linuxppc-dev at lists.ozlabs.org;
> devicetree at vger.kernel.org
> Subject: Re: [PATCH] Documentation: dts: fsl-usb: Document USB node
> compatible string for IP version
> 
> On Fri, 2014-08-22 at 00:05 -0500, Mehresh Ramneek-B31383 wrote:
> >
> > -----Original Message-----
> > From: Badola Nikhil-B46172
> > Sent: Friday, August 22, 2014 10:18 AM
> > To: Wood Scott-B07421
> > Cc: linuxppc-dev at lists.ozlabs.org; devicetree at vger.kernel.org; Mehresh
> > Ramneek-B31383
> > Subject: RE: [PATCH] Documentation: dts: fsl-usb: Document USB node
> > compatible string for IP version
> >
> > Adding Ramneek
> >
> > > -----Original Message-----
> > > From: Wood Scott-B07421
> > > Sent: Friday, August 22, 2014 3:53 AM
> > > To: Badola Nikhil-B46172
> > > Cc: linuxppc-dev at lists.ozlabs.org; devicetree at vger.kernel.org
> > > Subject: Re: [PATCH] Documentation: dts: fsl-usb: Document USB node
> > > compatible string for IP version
> > >
> > > On Thu, 2014-08-21 at 14:48 +0530, Nikhil Badola wrote:
> > > > Document compatible string containing IP version in USB device
> > > > tree node
> > > >
> > > > Signed-off-by: Nikhil Badola <nikhil.badola at freescale.com>
> > > > ---
> > > >  Documentation/devicetree/bindings/usb/fsl-usb.txt | 13
> > > > ++++++++-----
> > > >  1 file changed, 8 insertions(+), 5 deletions(-)
> > >
> > > Please CC devicetree at vger.kernel.org on all device tree patches (in
> > > addition to linuxppc-dev).
> > >
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/usb/fsl-usb.txt
> > > > b/Documentation/devicetree/bindings/usb/fsl-usb.txt
> > > > index 4779c02..5a3a0a8 100644
> > > > --- a/Documentation/devicetree/bindings/usb/fsl-usb.txt
> > > > +++ b/Documentation/devicetree/bindings/usb/fsl-usb.txt
> > > > @@ -10,7 +10,10 @@ Required properties :
> > > >     controllers, or "fsl-usb2-dr" for dual role USB controllers
> > > >     or "fsl,mpc5121-usb2-dr" for dual role USB controllers of MPC5121.
> > > >     Wherever applicable, the IP version of the USB controller should
> > > > -   also be mentioned (for eg. fsl-usb2-dr-v2.2 for bsc9132).
> > > > +   also be mentioned in another string.
> > > > +   For multi port host USB controller with IP version <IP_Ver>, it should
> be
> > > > +   "fsl-usb2-mph-<IP_Ver>". For dual role USB controller with IP version
> > > > +   <IP_Ver>, it should be "fsl-usb2-dr-<IP_Ver>".
> > >
> > > It was documented before -- this is just making it more explicit, right?
> > >
> > > FWIW, the version number can be read out of a USB register, so I'd
> > > rather remove the suggestion to specify the version number and
> > > replace it with a reference to the ID register.
> > we have following two issues -
> > (a) our USBIP version register doesn't have consistent "version field
> > size" over multiple version(s). This is why we couldn't use it for
> > reading version info across various IP versions
> > (b) this register is not exposed in all SoC RMs (probably because of
> > above reason)
> 
> :-(
> 
> If this is just a problem with older chips, we could have a new compatible name
> that designates the family of USB block versions with a sane version register.
> 
we could have done...but we have a requirement to write version specific code...
for instance, usb controller init sequence has changes from version 2.5 onwards...
then there are version specific errata fixe(s) also. Hence we decided to go for
compatible string containing hw ip version (major no.) so that our workaround/code is
consistent with hw ip version(s) published in errata(s)
 
> > > > @@ -55,9 +58,9 @@ Example multi port host USB controller device node :
> > > >  		port1;
> > > >  	};
> > > >
> > > > -Example dual role USB controller device node :
> > > > +Example dual role USB controller version 2.5 device node :
> > > >  	usb at 23000 {
> > > > -		compatible = "fsl-usb2-dr";
> > > > +		compatible = "fsl-usb2-dr-v2.5", "fsl-usb2-dr";
> > > >  		reg = <23000 1000>;
> > > >  		#address-cells = <1>;
> > > >  		#size-cells = <0>;
> > >
> > > This example doesn't correspond to any device tree I see.  Even
> > > after your next patch that sets t2080's USB to v2.5, the addresses are
> different.
> > >
> > I reckon that the example emphasizes on showing how IP version
> > information is to be stored in "compatible string". Is it necessary to
> > make sure that we should always site actual values already used?
> 
> The more realistic the examples are, the better.
> 
understood...we agree 

> -Scott
>