Messages in this thread | | | Date | Mon, 22 Dec 2014 09:05:38 -0800 | Subject | Re: [PATCH 2/2] USB: ehci-platform: Support ehci reset after resume quirk | From | Doug Anderson <> |
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Alan,
On Mon, Dec 22, 2014 at 8:06 AM, Alan Stern <stern@rowland.harvard.edu> wrote: > On Mon, 22 Dec 2014, Wu Liang feng wrote: > >> The EHCI controller doesn't properly detect the case when > > "The" EHCI controller? I don't know what EHCI controller you're > talking about, but my controllers don't have any trouble detecting > device removal during suspend.
This is specifically the EHCI controller on rk3288. Not sure why Wu Liang feng removed that part of the description.
>> a device is removed during suspend. Specifically,when we >> resume from suspend the EHCI controller maintaining the >> USB state (FLAG_CF is 1 Current Connect Status is 1) but >> a USB device (like a USB camera on rk3288) may have been >> disconnected actually. >> >> Let's add a quirk to force ehci to go into the >> usb_root_hub_lost_power() path and reset after resume. >> This should generally reset the whole controller and all >> ports and initialize everything cleanly again, and bring >> the devices back up. > > Isn't this solution too extreme? What if the device was a flash > storage drive and it wasn't unplugged during suspend? This patch would > force it to be removed, messing up any mounted filesystems, when there > was no need.
I'm told by Julius (CCed, who knows the USB stack infinitely better than I do) that you can work around this using "persist". I would imagine that anyone on a machine using hibernation would run into the same problem, right?
> Can you find a better way to work around the problem?
We asked a lot about this and you can find a whole set of detailed discussion at:
https://chromium-review.googlesource.com/#/c/232077/1/drivers/usb/host/ehci-platform.c
Since I don't know the USB subsystem particularly well, my review isn't terribly meaningful, but just in case:
Reviewed-by: Doug Anderson <dianders@chromium.org>
On rk3288-pinky I have tested that without this patch the EHCI controller flips out when a USB webcam is plugged into the port and is power cycled across suspend/resume. With this patch the controller properly unplugs / replugs the webcam.
Tested-by: Doug Anderson <dianders@chromium.org>
-Doug
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