linux-kernel - Re: [PATCH stable 5.4] usb: host: xhci-plat: add wakeup entry at sysfs

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Date:   Fri, 3 Feb 2023 09:50:35 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Matthias Kaehlcke <mka@...omium.org>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        "open list:USB XHCI DRIVER" <linux-usb@...r.kernel.org>
Subject: Re: [PATCH stable 5.4] usb: host: xhci-plat: add wakeup entry at
 sysfs

On 2/2/23 23:58, Greg Kroah-Hartman wrote:
> On Wed, Feb 01, 2023 at 03:19:08PM -0800, Florian Fainelli wrote:
>> On 2/1/23 10:16, Greg Kroah-Hartman wrote:
>>> On Wed, Feb 01, 2023 at 09:44:04AM -0800, Florian Fainelli wrote:
>>>> From: Peter Chen <peter.chen@....com>
>>>>
>>>> commit  4bb4fc0dbfa23acab9b762949b91ffd52106fe4b upstream
>>>>
>>>> With this change, there will be a wakeup entry at /sys/../power/wakeup,
>>>> and the user could use this entry to choose whether enable xhci wakeup
>>>> features (wake up system from suspend) or not.
>>>>
>>>> Tested-by: Matthias Kaehlcke <mka@...omium.org>
>>>> Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
>>>> Signed-off-by: Peter Chen <peter.chen@....com>
>>>> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
>>>> Link: https://lore.kernel.org/r/20200918131752.16488-6-mathias.nyman@linux.intel.com
>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>>> ---
>>>>    drivers/usb/host/xhci-plat.c | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> Why is this new feature needed on these older kernels?  What does it fix
>>> that is broken?
>>
>> It fixes the inability to make the XHCI controller a wake-up device since
>> there is no /sys/*/*xhci/power/wakeup sysfs entry to manipulate unless this
>> patch is applied.
> 
> But that is a new feature, not a bugfix.

Support for wake-up was already there in the xhci driver, just there was 
no way to activate it from user-space, that seems like a fix to me.

> 
> What systems need this for these older kernels that will actually update
> to them in order to pick up this change?

Some NXP systems required that, and all of our ARCH_BRCMSTB SoCs also 
have that capability, I see you applied those patches, thanks!
-- 
Florian