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From: Alan Stern <stern@rowland.harvard.edu>
To: Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc: mathias.nyman@intel.com, <gregkh@linuxfoundation.org>,
	<linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] Revert "usb: Avoid unnecessary LPM enabling and disabling during suspend and resume"
Date: Wed, 2 Oct 2019 11:47:39 -0400 (EDT)
Message-ID: <Pine.LNX.4.44L0.1910021146260.1552-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20191002151512.28517-1-kai.heng.feng@canonical.com>

On Wed, 2 Oct 2019, Kai-Heng Feng wrote:

> This reverts commit d590c23111505635e1beb01006612971e5ede8aa.
> 
> Dell WD15 dock has a topology like this:
> /:  Bus 04.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/2p, 10000M
>     |__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/7p, 5000M
>             |__ Port 2: Dev 3, If 0, Class=Vendor Specific Class, Driver=r8152, 5000M
> 
> Their IDs:
> Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
> Bus 004 Device 002: ID 0424:5537 Standard Microsystems Corp.
> Bus 004 Device 004: ID 0bda:8153 Realtek Semiconductor Corp.
> 
> Ethernet cannot be detected after plugging ethernet cable to the dock,
> the hub and roothub get runtime resumed and runtime suspended
> immediately:
> ...

> After some trial and errors, the issue goes away if LPM on the SMSC hub
> is disabled. Digging further, enabling and disabling LPM during runtime
> resume and runtime suspend respectively can solve the issue.
> 
> So bring back the old LPM behavior, which the SMSC hub inside Dell WD15
> depends on.
> 
> Fixes: d590c2311150 ("usb: Avoid unnecessary LPM enabling and disabling during suspend and resume")
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

Maybe it would be better to have a VID/PID-specific quirk for this?

Alan Stern


  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 15:15 Kai-Heng Feng
2019-10-02 15:47 ` Alan Stern [this message]
2019-10-03 11:55   ` Kai-Heng Feng
2019-10-03 14:26     ` Alan Stern
2019-10-03 14:57       ` Kai-Heng Feng
2019-10-03 15:56 ` [PATCH v2] usb: Add a new quirk to let buggy hub enable and disable LPM during suspend and resume Kai-Heng Feng
2019-10-03 16:02   ` Greg KH
2019-10-03 17:24   ` [PATCH v3] " Kai-Heng Feng
2019-10-03 19:04     ` Alan Stern
2019-10-17  6:33       ` Kai-Heng Feng
2019-10-18 18:59         ` Greg Kroah-Hartman
2019-10-21 13:59           ` Mathias Nyman
2019-10-21 18:40             ` Kai-Heng Feng

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