linux-kernel - Re: [PATCH 2/2] twl4030_charger: find associated phy by more reliable means.

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Date:	Wed, 4 Mar 2015 20:14:31 +1100
From:	NeilBrown <neilb@...e.de>
To:	Sebastian Reichel <sre@...nel.org>
Cc:	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Felipe Balbi <balbi@...com>,
	GTA04 owners <gta04-owner@...delico.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH 2/2] twl4030_charger: find associated phy by more
 reliable means.

On Wed, 25 Feb 2015 22:13:51 +0100 Sebastian Reichel <sre@...nel.org> wrote:

> Hi Neil,
> 
> On Tue, Feb 24, 2015 at 03:01:29PM +1100, NeilBrown wrote:
> > twl4030_charger currently finds the associated phy
> > using usb_get_phy() which will return the first USB2 phy.
> > If your platform has multiple such phys (as mine does),
> > this is not reliable (and reliably fails on the GTA04).
> > 
> > Change to use devm_usb_get_phy_by_node(), having found the
> > node by looking for an appropriately named sibling in
> > device-tree.
> > 
> > This makes usb-charging dependent on correct device-tree
> > configuration.
> 
> The patch looks ok to me, but you should update the DT documentation
> in Documentation/devicetree/bindings/power/twl-charger.txt regarding
> the sibling dependency.
> 
> Apart from that DT binding maintainers should be CC'd.
> 
> -- Sebastian

Thanks.
I've added the following.  I've also changed the code to use
of_find_compatible_node() and find the USB phy based on 'compatible' rather
than on the node name.

I'll Cc DT maintainers when I resubmit.

Thanks,
NeilBrown

diff --git a/Documentation/devicetree/bindings/power/twl-charger.txt b/Documentation/devicetree/bindings/power/twl-charger.txt
index d5c706216df5..3b4ea1b73b38 100644
--- a/Documentation/devicetree/bindings/power/twl-charger.txt
+++ b/Documentation/devicetree/bindings/power/twl-charger.txt
@@ -1,5 +1,15 @@
 TWL BCI (Battery Charger Interface)
 
+The battery charger needs to interact with the USB phy in order
+to know when charging is permissible, and when there is a connection
+or disconnection.
+
+The choice of phy cannot be configured at a hardware level, so there
+is no value in explicit configuration in device-tree.  Rather
+if there is a sibling of the BCI node which is compatible with
+"ti,twl4030-usb", then that is used to determine when and how
+use USB power for charging.
+
 Required properties:
 - compatible:
   - "ti,twl4030-bci"
diff --git a/Documentation/devicetree/bindings/usb/twlxxxx-usb.txt b/Documentation/devicetree/bindings/usb/twlxxxx-usb.txt
index 0aee0ad3f035..17327a296110 100644
--- a/Documentation/devicetree/bindings/usb/twlxxxx-usb.txt
+++ b/Documentation/devicetree/bindings/usb/twlxxxx-usb.txt
@@ -30,6 +30,9 @@ TWL4030 USB PHY AND COMPARATOR
  - usb_mode : The mode used by the phy to connect to the controller. "1"
    specifies "ULPI" mode and "2" specifies "CEA2011_3PIN" mode.
 
+If a sibling node is compatible "ti,twl4030-bci", then it will find
+this device and query it for USB power status.
+
 twl4030-usb {
 	compatible = "ti,twl4030-usb";
 	interrupts = < 10 4 >;

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