linux-kernel - Re: [PATCH v6 8/8] usb: ehci-exynos: Change to use phy provided by the generic phy framework

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Message-ID: <CAOesGMgKQrW=Rb6ZtpOVKAZ6dDzy82CzbmOJtKRb8x6JaS1QLg@mail.gmail.com>
Date:	Wed, 29 Jan 2014 12:55:19 -0800
From:	Olof Johansson <olof@...om.net>
To:	Kamil Debski <k.debski@...sung.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Tomasz Figa <t.figa@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Vivek Gautam <gautam.vivek@...sung.com>,
	mat.krawczuk@...il.com, yulgon.kim@...sung.com,
	p.paneri@...sung.com, av.tikhomirov@...sung.com,
	Jingoo Han <jg1.han@...sung.com>,
	Kumar Gala <galak@...eaurora.org>,
	Matt Porter <matt.porter@...aro.org>,
	tjakobi@...h.uni-bielefeld.de,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH v6 8/8] usb: ehci-exynos: Change to use phy provided by
 the generic phy framework

Hi,

On Wed, Jan 29, 2014 at 9:29 AM, Kamil Debski <k.debski@...sung.com> wrote:
> Change the phy provider used from the old one using the USB phy
> framework to a new one using the Generic phy framework.
>
> Signed-off-by: Kamil Debski <k.debski@...sung.com>
> ---
>  .../devicetree/bindings/usb/exynos-usb.txt         |   13 +++
>  drivers/usb/host/ehci-exynos.c                     |   97 +++++++++++++-------
>  2 files changed, 76 insertions(+), 34 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/usb/exynos-usb.txt b/Documentation/devicetree/bindings/usb/exynos-usb.txt
> index d967ba1..25e199a 100644
> --- a/Documentation/devicetree/bindings/usb/exynos-usb.txt
> +++ b/Documentation/devicetree/bindings/usb/exynos-usb.txt
> @@ -12,6 +12,10 @@ Required properties:
>   - interrupts: interrupt number to the cpu.
>   - clocks: from common clock binding: handle to usb clock.
>   - clock-names: from common clock binding: Shall be "usbhost".
> +  - port: if in the SoC there are EHCI phys, they should be listed here.
> +One phy per port. Each port should have its reg entry with a consecutive
> +number. Also it should contain phys and phy-names entries specifying the
> +phy used by the port.
>
>  Optional properties:
>   - samsung,vbus-gpio:  if present, specifies the GPIO that
> @@ -27,6 +31,15 @@ Example:
>
>                 clocks = <&clock 285>;
>                 clock-names = "usbhost";
> +
> +               #address-cells = <1>;
> +               #size-cells = <0>;
> +               port@0 {
> +                   reg = <0>;
> +                   phys = <&usb2phy 1>;
> +                   phy-names = "host";
> +                   status = "disabled";
> +               };
>         };
>
>  OHCI

[...]

> @@ -102,14 +132,26 @@ static int exynos_ehci_probe(struct platform_device *pdev)
>                                         "samsung,exynos5440-ehci"))
>                 goto skip_phy;
>
> -       phy = devm_usb_get_phy(&pdev->dev, USB_PHY_TYPE_USB2);
> -       if (IS_ERR(phy)) {
> -               usb_put_hcd(hcd);
> -               dev_warn(&pdev->dev, "no platform data or transceiver defined\n");
> -               return -EPROBE_DEFER;
> -       } else {
> -               exynos_ehci->phy = phy;
> -               exynos_ehci->otg = phy->otg;
> +       for_each_available_child_of_node(pdev->dev.of_node, child) {
> +               err = of_property_read_u32(child, "reg", &phy_number);
> +               if (err) {
> +                       dev_err(&pdev->dev, "Failed to parse device tree\n");
> +                       of_node_put(child);
> +                       return err;
> +               }
> +               if (phy_number >= PHY_NUMBER) {
> +                       dev_err(&pdev->dev, "Failed to parse device tree - number out of range\n");
> +                       of_node_put(child);
> +                       return -EINVAL;
> +               }
> +               phy = devm_of_phy_get(&pdev->dev, child, 0);
> +               of_node_put(child);
> +               if (IS_ERR(phy)) {
> +                       dev_err(&pdev->dev, "Failed to get phy number %d",
> +                                                               phy_number);
> +                       return PTR_ERR(phy);
> +               }
> +               exynos_ehci->phy[phy_number] = phy;

this looks like it is now breaking older device trees, where ports
might not be described. Since device tree interfaces need to be
backwards compatible, you still need to handle the old case of not
having ports described.

There are two ways of doing this:

1. Fall back to the old behavior if there are no ports
2. Use a new compatible value for the new model with port subnodes,
and if the old compatible value is used, then fall back to the old
behavior.

I'm guessing (1) might be easiest since you can check for the presence
of #address-cells to tell if this is just an old style node, or if
it's a new-style node without any ports below it.


-Olof
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