linux-kernel - Re: [v1 1/1] usb:host:xhci support option to disable xHCI 1.0 USB2 HW LPM

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Date:   Thu, 18 May 2017 17:30:26 -0500
From:   Rob Herring <robh@...nel.org>
To:     "Thang Q. Nguyen" <tqnguyen@....com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Mark Rutland <mark.rutland@....com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Phong Vo <pvo@....com>,
        Loc Ho <lho@....com>, Duc Tran <dxtran@....com>,
        Quang Han <qhan@....com>, Tung Nguyen <tunguyen@....com>,
        patches@....com
Subject: Re: [v1 1/1] usb:host:xhci support option to disable xHCI 1.0 USB2
 HW LPM

On Sat, May 13, 2017 at 07:13:14AM +0700, Thang Q. Nguyen wrote:
> XHCI specification 1.1 does not require xHCI 1.0 compliant controllers
> to always enable hardware USB2 LPM.
> However, the current xHCI driver always enable it by setting HLE=1 when
> seeing HLC=1. This makes certain xHCI controllers that have broken USB2
> HW LPM fail to work as there is no way to disable this feature.
> This patch adds support to control disabling USB2 Hardware LPM via
> DT/ACPI attribute.
> 
> Signed-off-by: Tung Nguyen <tunguyen@....com>
> Signed-off-by: Thang Q. Nguyen <tqnguyen@....com>
> ---
>  Documentation/devicetree/bindings/usb/usb-xhci.txt |    1 +
>  drivers/usb/host/xhci-plat.c                       |    3 +++
>  drivers/usb/host/xhci.c                            |    7 ++++++-
>  drivers/usb/host/xhci.h                            |    1 +
>  4 files changed, 11 insertions(+), 1 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/usb-xhci.txt b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> index 2d80b60..b5da569 100644
> --- a/Documentation/devicetree/bindings/usb/usb-xhci.txt
> +++ b/Documentation/devicetree/bindings/usb/usb-xhci.txt
> @@ -26,6 +26,7 @@ Required properties:
>  
>  Optional properties:
>    - clocks: reference to a clock
> +  - usb2-hle-disable: disable USB2 LPM for hardware does not support it
>    - usb3-lpm-capable: determines if platform is USB3 LPM capable

Can we have some consistency in the naming of these 2 properties? At 
least use 'lpm' rather than 'hle'. I don't recall why the 2nd one is not 
default enabled, but that would make more sense.

>    - quirk-broken-port-ped: set if the controller has broken port disable mechanism
>