linux-kernel - Re: [RFC 3/7] dt: bindings: Add nokia-bluetooth

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Date:	Wed, 17 Aug 2016 01:28:55 +0200
From:	Sebastian Reichel <sre@...nel.org>
To:	Rob Herring <robh@...nel.org>
Cc:	Tony Lindgren <tony@...mide.com>,
	Mark Rutland <mark.rutland@....com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.com>, Ville Tervo <ville.tervo@....fi>,
	Filip Matijević <filip.matijevic.pz@...il.com>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Pavel Machek <pavel@....cz>,
	Pali Rohár <pali.rohar@...il.com>,
	ivo.g.dimitrov.75@...il.com, linux-bluetooth@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-omap@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 3/7] dt: bindings: Add nokia-bluetooth

Hi Rob,

On Tue, Aug 16, 2016 at 08:51:55AM -0500, Rob Herring wrote:
> On Sat, Aug 13, 2016 at 05:14:34AM +0200, Sebastian Reichel wrote:
> > ---
> >  .../devicetree/bindings/net/nokia-bluetooth.txt    | 43 ++++++++++++++++++++++
> >  1 file changed, 43 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/net/nokia-bluetooth.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/net/nokia-bluetooth.txt b/Documentation/devicetree/bindings/net/nokia-bluetooth.txt
> > new file mode 100644
> > index 000000000000..a0fceabb4cce
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/net/nokia-bluetooth.txt
> > @@ -0,0 +1,43 @@
> > +Nokia bluetooth UART devices
> > +------
> > +
> > +Some vendors have custom versions of their chips, that can be found in Nokia
> > +devices. These chips are controlled differently, than the non-Nokia version,
> > +so a different binding is required. All chips listed here implement the Nokia
> > +H4+ protocol.
> > +
> > +Required properties:
> > +
> > +  - compatible: should be one of the following:
> > +	* "nokia,brcm,bcm2048"
> > +	* "nokia,ti,wl1271-bluetooth"
> 
> Perhaps these should be 2 separate strings. Something like 
> '"nokia,n900-bt", "brcm,bcm2048"'. However, if they are in no way 
> compatible with the default version from the vendors, then just a single 
> string is fine, but it doesn't need to be aligned to the vendor 
> compatible string. So just "nokia,n900-bcm2048" or similar is fine.

The default bcm2048 variant uses different initialization process
and does not use word alignment as far as I know. I think having
"brcm,bcm2048" in the compatible string is wrong.

I guess "brcm,bcm2048-nokia" would also be an option, since the
chip has been built buy broadcom, but it has a custom Nokia
interface.

> > +  - reset-gpios:		Should specify the gpio for bluetooth reset
> > +  - host-wakeup-gpios:		Should specify the gpio for host wakeup
> 
> Should be interrupt instead?

Yes this is mostly an interrupt, but I need to read the current
line state.

> > +  - bluetooth-wakeup-gpios:	Should specify the gpio for bluetooth wakeup
> 
> State direction and active state for gpios.

ok.

> > +  - clock-names:		Should be "sysclk"
> > +  - clocks:			Should contain a clock phandle for system clock
> > +
> > +Example:
> > +
> > +/ {
> > +	/* controlled (enabled/disabled) directly by wl1271 */
> > +	vctcxo: vctcxo {
> > +		compatible = "fixed-clock";
> > +		#clock-cells = <0>;
> > +		clock-frequency = <38400000>;
> > +	};
> > +};
> > +
> > +&uart2 {
> 
> I want to see a common serial device binding doc before accepting any 
> device bindings. It's not going to say much initially other than devices 
> are child nodes of uarts. Perhaps something on baudrate settings.

Neil added a short sentence about this in "[RFC 2/7] tty: add
support for "tty slave" devices". I just took the unmodified patch
from Neil (*), so it's not in its own patch.

> > +	bluetooth {
> > +		compatible = "nokia,ti,wl1271-bluetooth";
> > +
> > +		reset-gpios = <&gpio1 26 GPIO_ACTIVE_HIGH>; /* 26 */
> > +		host-wakeup-gpios = <&gpio4 5 GPIO_ACTIVE_HIGH>; /* 101 */
> > +		bluetooth-wakeup-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>; /* 37 */
> > +
> > +		clocks = <&vctcxo>;
> > +		clock-names = "sysclk";
> > +	};
> > +
> > +};

-- Sebastian

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