Re: [Patch v5 08/13] ARM: imx6q: add config-on-boot gpios

On 06/20/2012 08:29 AM, Rob Herring wrote:

On 06/13/2012 08:33 PM, Richard Zhao wrote:

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On Wed, Jun 13, 2012 at 11:50:35AM -0500, Rob Herring wrote:

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On 06/13/2012 10:28 AM, Richard Zhao wrote:

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On Wed, Jun 13, 2012 at 10:09:54AM -0500, Rob Herring wrote:

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On 06/13/2012 07:34 AM, Richard Zhao wrote:

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Sometimes, boards have gpios that don't own by any driver or owner
by a generic driver that don't like hacks. Such gpios is normally
output and need setup once on boot. So I introduce the config-on-boot
gpios.

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diff --git a/Documentation/devicetree/bindings/arm/config-on-boot.txt b/Documentation/devicetree/bindings/arm/config-on-boot.txt

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+Node name: config-on-boot
+  It must be in root node. config-on-boot means to describe settings that needs
+  to be set one time on boot but aren't owned by any driver, or the owned driver
+  is too generic to handle such settings. For example, usb hub uses generic
+  driver in usb core code, a on-board usb may need deassert reset pin.

NAK. This is not a h/w description

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You need to describe that you have a hub on the usb bus and add the gpio
line to that node. Just like PCI is probe-able, you still need DT nodes
sometimes for cases like this.

PCI has dev id and may add quirks. But for embedded, I don't know how
to connect a of node to a hub device enumerated by usb core code. And
it may also pollute the usb core code.

USB also uses device and manufacturer ids. One of the main reasons for
putting pci devices into dts is to describe out of band signals just
like this.

Creating a binding and support code for full usb bus topology would be a
lot of work which is why I propose a simpler approach below.

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A simpler approach would be to just add
the gpio to the ehci controller node, but that's not exactly correct.

That's exactly why this patch comes out.

I mean just something like "fsl,hub-reset-gpios" in the ehci device
node. It's at least under a usb node. Whether the ehci driver handles
this or you just have a separate piece of code to find this property and
setup the gpio is up to you.

I haven't been following the thread, but just noticed it. Very similar
things (DT nodes for probed devices) are coming up quite a bit recently,
for example:

Re: Where to power on the wifi device before loading the driver.
http://www.spinics.net/lists/arm-kernel/msg180368.html

dt: rfkill-gpio: add bindings documentation
http://www.spinics.net/lists/linux-tegra/msg03977.html

I wonder if there's any kind of infra-structure or standardized bindings
that would be useful here?
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