From: Kai-Heng Feng <kai.heng.feng@canonical.com>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Mathias Nyman <mathias.nyman@linux.intel.com>,
Linux USB List <linux-usb@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] USB: Disable USB2 LPM at shutdown
Date: Mon, 5 Aug 2019 20:58:33 +0800 [thread overview]
Message-ID: <27A5C1CC-E0A4-4CAF-B81E-90EE76C8A887@canonical.com> (raw)
In-Reply-To: <46147522-7BC2-4C30-B3E5-6568E9642982@canonical.com>
Hi Greg,
at 17:22, Kai-Heng Feng <kai.heng.feng@canonical.com> wrote:
> at 22:17, Alan Stern <stern@rowland.harvard.edu> wrote:
>>
>> I agree with Kai-Heng, this seems like a fairly light-weight solution
>> to a reasonable problem.
>
> Thanks for your review.
>
>> As to the issue of how much it will slow down system shutdowns, I have
>> no idea. Probably not very much, unless somebody has an unusually
>> large number of USB devices plugged in, but only testing can give a
>> real answer.
>
> In addition to that, only USB2 devices that enable LPM will slow down
> shutdown process.
> Right now only internally connected USB2 devices enable LPM, so the
> numbers are even lower.
>
>> I suppose we could add an HCD flag for host controllers which require
>> this workaround. Either way, it's probably not a very big deal.
>
> IMO this is not necessary. Only xHCI that reports hw_lpm_support will be
> affected. At least for PC, this only became true after Whiskey Lake.
>
> Kai-Heng
>
>> Alan Stern
This patch is included in Ubuntu’s kernel for a while now, and there’s no
regression report so far.
Please consider merge this patch.
Kai-Heng
next prev parent reply other threads:[~2019-08-05 12:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-24 6:16 [PATCH v2] USB: Disable USB2 LPM at shutdown Kai-Heng Feng
2019-01-30 8:21 ` Greg KH
2019-01-30 16:01 ` Kai-Heng Feng
2019-03-12 10:22 ` Kai-Heng Feng
2019-04-11 7:55 ` Kai-Heng Feng
2019-06-06 8:06 ` Kai-Heng Feng
2019-06-06 14:17 ` Alan Stern
2019-06-08 9:22 ` Kai-Heng Feng
2019-08-05 12:58 ` Kai-Heng Feng [this message]
2019-08-05 13:06 ` Greg KH
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