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19d41a2899
This patch schedules a USB reset device call following a USB clear halt error. The issues solved, and patch implementation, are similar to those found in drivers/hid/usbhid/hid-core.c. As seen on very rare occasions approximately one time per month (mceusb device 2304:0225 in this sample) Jul 27 2018 15:09:39 [59388.696941] mceusb 1-1.1.2:1.0: Error: urb status = -32 (RX HALT) [59388.698838] mceusb 1-1.1.2:1.0: rx clear halt error -32 the device can get into RX or TX HALT state where usb_clear_halt() also fails and also returns -EPIPE (HALT/STALL). After which, all further mceusb device control and data I/O always fail with HALT/STALL. Subsequently, the entire mceusb device no longer functions. Cause and problem replication conditions remain unknown. Further troubleshooting reveals usb_reset_device() restores mceusb device operation. Patch test 1: Hot unplugging the mceusb device triggers USB RX HALT and USB clear halt errors. A mceusb_dev_disconnect() call follows unplug. This patch's reset device call invokes an extra mceusb_dev_probe() mceusb_dev_disconnect() cycle, before the mceusb driver detaches. The additional probe/disconnect verifies the patch's device reset code executed. But note this patch is for USB clear halt error cases not caused by unplugging the mceusb device. Patch test 2: Simulate a RX HALT and a clear halt error with instrumented code in the driver. Jul 12 2019 19:41:18 [522745.263104] mceusb 1-1.3:1.0: set rx halt retval, 0 [522745.263943] mceusb 1-1.3:1.0: Error: rx urb status = -32 (RX HALT) [522745.263970] mceusb 1-1.3:1.0: kevent 1 scheduled [522745.264016] mceusb 1-1.3:1.0: kevent handler called (flags 0x2) [522745.272883] mceusb 1-1.3:1.0: rx clear halt status = 0 [522745.272917] mceusb 1-1.3:1.0: stuck RX HALT state requires USB Reset Device to clear [522745.273005] mceusb 1-1.3:1.0: mceusb_dev_disconnect called [522745.702815] usb 1-1.3: reset full-speed USB device number 14 using dwc_otg [522745.836812] mceusb 1-1.3:1.0: mceusb_dev_probe called [522745.836823] mceusb 1-1.3:1.0: acceptable bulk inbound endpoint found [522745.836832] mceusb 1-1.3:1.0: acceptable bulk outbound endpoint found ... The result matches what is expected when the device gets into a real rx clear halt error case by itself. This is the same sequence of messages when manually invoking the ./usbreset command line utility with an unpatched mceusb driver. Signed-off-by: A Sun <as1033x@comcast.net> Signed-off-by: Sean Young <sean@mess.org> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.