forked from luck/tmp_suning_uos_patched
a40178b2fa
Problem Summary: Problem has been observed generally with PM states where VBUS goes off during suspend. There are some SS USB devices which take longer time for link training compared to many others. Such devices fail to reconnect with same old address which was associated with it before suspend. When system resumes, at some point of time (dpm_run_callback-> usb_dev_resume->usb_resume->usb_resume_both->usb_resume_device-> usb_port_resume) SW reads hub status. If device is present, then it finishes port resume and re-enumerates device with same address. If device is not present then, SW thinks that device was removed during suspend and therefore does logical disconnection and removes all the resource allocated for this device. Now, if I put sufficient delay just before root hub status read in usb_resume_device then, SW sees always that device is present. In normal course(without any delay) SW sees that no device is present and then SW removes all resource associated with the device at this port. In the latter case, after sometime, device says that hey I am here, now host enumerates it, but with new address. Problem had been reproduced when I connect verbatim USB3.0 hard disc with my STiH407 XHCI host running with 3.10 kernel. I see that similar problem has been reported here. https://bugzilla.kernel.org/show_bug.cgi?id=53211 Reading above it seems that bug was not in 3.6.6 and was present in 3.8 and again it was not present for some in 3.12.6, while it was present for few others. I tested with 3.13-FC19 running at i686 desktop, problem was still there. However, I was failed to reproduce it with 3.16-RC4 running at same i686 machine. I would say it is just a random observation. Problem for few devices is always there, as I am unable to find a proper fix for the issue. So, now question is what should be the amount of delay so that host is always able to recognize suspended device after resume. XHCI specs 4.19.4 says that when Link training is successful, port sets CSC bit to 1. So if SW reads port status before successful link training, then it will not find device to be present. USB Analyzer log with such buggy devices show that in some cases device switch on the RX termination after long delay of host enabling the VBUS. In few other cases it has been seen that device fails to negotiate link training in first attempt. It has been reported till now that few devices take as long as 2000 ms to train the link after host enabling its VBUS and RX termination. This patch implements a 2000 ms timeout for CSC bit to set ie for link training. If in a case link trains before timeout, loop will exit earlier. This patch implements above delay, but only for SS device and when persist is enabled. So, for the good device overhead is almost none. While for the bad devices penalty could be the time which it take for link training. But, If a device was connected before suspend, and was removed while system was asleep, then the penalty would be the timeout ie 2000 ms. Results: Verbatim USB SS hard disk connected with STiH407 USB host running 3.10 Kernel resumes in 461 msecs without this patch, but hard disk is assigned a new device address. Same system resumes in 790 msecs with this patch, but with old device address. Cc: <stable@vger.kernel.org> Signed-off-by: Pratyush Anand <pratyush.anand@st.com> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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| atm | ||
| c67x00 | ||
| chipidea | ||
| class | ||
| common | ||
| core | ||
| dwc2 | ||
| dwc3 | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| misc | ||
| mon | ||
| musb | ||
| phy | ||
| renesas_usbhs | ||
| serial | ||
| storage | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| README | ||
| usb-skeleton.c | ||
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.