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

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Message-ID: <d80dab04-eeff-373c-a629-b09ec288b2ad@ti.com>
Date:   Thu, 3 Nov 2016 22:04:48 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Alexandre Bailon <abailon@...libre.com>, <david@...hnology.com>,
        <b-liu@...com>, <balbi@...nel.org>
CC:     <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

Hi,

On Thursday 03 November 2016 08:56 PM, 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.

I think we do just that if we populate dr_mode with host or peripheral. Why do
we need another property to control dr_mode property?
> 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.

>From what I understand from the previous patch, if VBUS sense and the session
end comparator is enabled, the controller can work in host mode or device mode.

Thanks
Kishon