linux-kernel - Re: [PATCH v3 09/12] usb: roles: Add Intel xHCI USB role switch driver

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Date:   Mon, 26 Feb 2018 13:42:11 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v3 09/12] usb: roles: Add Intel xHCI USB role switch
 driver

On Mon, Feb 26, 2018 at 10:09:22AM +0100, Hans de Goede wrote:
> Various Intel SoCs (Cherry Trail, Broxton and others) have an internal USB
> role switch for swiching the OTG USB data lines between the xHCI host
> controller and the dwc3 gadget controller.
> 
> Note on some Cherry Trail systems there is ACPI/AML code listening to
> edge interrupts on the id-pin (through an _AIE ACPI method) and switching
> the role between ROLE_HOST and ROLE_NONE based on the id-pin. Note it does
> not set the role to ROLE_DEVICE, because device-mode is usually not used
> under Windows.
> 
> The presence of AML code which modifies the cfg0 reg (on some systems)
> means that our read/write/modify of cfg0 may race with the AML code
> doing the same to avoid this we take the global ACPI lock while doing
> the read/write/modify.
> 
> Signed-off-by: Hans de Goede <hdegoede@...hat.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

Thanks Hans!

-- 
heikki