linux-kernel - Re: [PATCH v3 3/5] dt/bindings: Add a new property to DA8xx USB PHY

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Message-ID: <eddbe116-b504-296b-8fe3-4e4debee3a98@lechnology.com>
Date:   Thu, 3 Nov 2016 11:53:14 -0500
From:   David Lechner <david@...hnology.com>
To:     Alexandre Bailon <abailon@...libre.com>, b-liu@...com,
        balbi@...nel.org
Cc:     kishon@...com, khilman@...libre.com, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, nsekhar@...com
Subject: Re: [PATCH v3 3/5] dt/bindings: Add a new property to DA8xx USB PHY

On 11/03/2016 10:26 AM, Alexandre Bailon wrote:
> The USB PHY is able to operate in OTG, host or peripheral.
> Some board may be wired to work act only as host or peripheral.
> In such case, the dr_mode property of controller must be set to
> host or peripheral. But doing that will also configure the PHY
> in host or peripheral mode whereas OTG is able to detect which
> role the USB controller should take.
> The PHY's host or peripheral mode are actually only useful when
> hardware doesn't allow OTG to detect it's role.
>
> Add the usb20_force_mode property to force the PHY to operate
> in host or peripheral mode.

Device tree describes the hardware, not the configuration, so this is 
not acceptable.

Besides, this setting should not be fixed to one value anyway.

> When usb20_force_mode is used, dr_mode should also be configured
> to host or peripheral.
> The controller uses dr_mode to configure itself, but the phy use
> it to get the mode to use to configure the PHY mode.
>
> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> ---
>  Documentation/devicetree/bindings/phy/phy-da8xx-usb.txt | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/phy/phy-da8xx-usb.txt b/Documentation/devicetree/bindings/phy/phy-da8xx-usb.txt
> index c26478b..9fc87fb 100644
> --- a/Documentation/devicetree/bindings/phy/phy-da8xx-usb.txt
> +++ b/Documentation/devicetree/bindings/phy/phy-da8xx-usb.txt
> @@ -4,6 +4,11 @@ Required properties:
>   - compatible: must be "ti,da830-usb-phy".
>   - #phy-cells: must be 1.
>
> +Optional properties:
> +- usb20-force-mode: Force the phy to operate in same mode than the USB OTG controller.
> +		    It should only be defined if the hardware is not capable correctly
> +		    detect the role of USB by using VBUS and ID pin.
> +
>  This device controls the PHY for both the USB 1.1 OHCI and USB 2.0 OTG
>  controllers on DA8xx SoCs. Consumers of this device should use index 0 for
>  the USB 2.0 phy device and index 1 for the USB 1.1 phy device.
>