linux-kernel - Re: [PATCH 02/21] usb: ulpi: Support device discovery via DT

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Message-ID: <20160628205642.GP3737@rob-hp-laptop>
Date:	Tue, 28 Jun 2016 15:56:42 -0500
From:	Rob Herring <robh@...nel.org>
To:	Stephen Boyd <stephen.boyd@...aro.org>
Cc:	linux-usb@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	Andy Gross <andy.gross@...aro.org>,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Neil Armstrong <narmstrong@...libre.com>,
	Arnd Bergmann <arnd@...db.de>, Felipe Balbi <balbi@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 02/21] usb: ulpi: Support device discovery via DT

On Sun, Jun 26, 2016 at 12:28:19AM -0700, Stephen Boyd wrote:
> The qcom HSIC ulpi phy doesn't have any bits set in the vendor or
> product id ulpi registers. This makes it impossible to make a
> ulpi driver match against the id registers. Add support to
> discover the ulpi phys via DT to help alleviate this problem.
> We'll look for a ulpi bus node underneath the device registering
> the ulpi viewport (or the parent of that device to support
> chipidea's device layout) and then match up the phy node
> underneath that with the ulpi device that's created.
> 
> The side benefit of this is that we can use standard DT
> properties in the phy node like clks, regulators, gpios, etc.
> because we don't have firmware like ACPI to turn these things on
> for us. And we can use the DT phy binding to point our phy
> consumer to the phy provider.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Cc: <devicetree@...r.kernel.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Signed-off-by: Stephen Boyd <stephen.boyd@...aro.org>
> ---
>  Documentation/devicetree/bindings/usb/ulpi.txt | 20 +++++++++
>  drivers/usb/common/ulpi.c                      | 56 +++++++++++++++++++++++++-
>  2 files changed, 74 insertions(+), 2 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/usb/ulpi.txt
> 
> diff --git a/Documentation/devicetree/bindings/usb/ulpi.txt b/Documentation/devicetree/bindings/usb/ulpi.txt
> new file mode 100644
> index 000000000000..ca179dc4bd50
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/usb/ulpi.txt
> @@ -0,0 +1,20 @@
> +ULPI bus binding
> +----------------
> +
> +Phys that are behind a ULPI connection can be described with the following
> +binding. The host controller shall have a "ulpi" named node as a child, and
> +that node shall have one enabled node underneath it representing the ulpi
> +device on the bus.

This needs to co-exist with the USB bus binding which has the controller 
ports for the child nodes. Maybe use the phy binding?

> +
> +EXAMPLE
> +-------
> +
> +usb {
> +	compatible = "vendor,usb-controller";
> +
> +	ulpi {
> +		phy {
> +			compatible = "vendor,phy";
> +		};
> +	};
> +};