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In DWC_usb31 version 1.70a-ea06 and prior, for highspeed and fullspeed isochronous IN, BIT[15:14] of the 16-bit microframe number reported by the XferNotReady event are invalid. The driver uses this number to schedule the isochronous transfer and passes it to the START TRANSFER command. Because this number is invalid, the command may fail. If BIT[15:14] matches the internal 16-bit microframe, the START TRANSFER command will pass and the transfer will start at the scheduled time, if it is off by 1, the command will still pass, but the transfer will start 2 seconds in the future. For all other conditions, the START TRANSFER command will fail with bus-expiry. In order to workaround this issue, we can test for the correct combination of BIT[15:14] by sending START TRANSFER commands with different values of BIT[15:14]: 'b00, 'b01, 'b10, and 'b11. Each combination is 2^14 uframe apart (or 2 seconds). 4 seconds into the future will result in a bus-expiry status. As the result, within the 4 possible combinations for BIT[15:14], there will be 2 successful and 2 failure START COMMAND status. One of the 2 successful command status will result in a 2-second delay start. The smaller BIT[15:14] value is the correct combination. Since there are only 4 outcomes and the results are ordered, we can simply test 2 START TRANSFER commands with BIT[15:14] combinations 'b00 and 'b01 to deduce the smaller successful combination. Let test0 = test status for combination 'b00 and test1 = test status for 'b01 of BIT[15:14]. The correct combination is as follow: if test0 fails and test1 passes, BIT[15:14] is 'b01 if test0 fails and test1 fails, BIT[15:14] is 'b10 if test0 passes and test1 fails, BIT[15:14] is 'b11 if test0 passes and test1 passes, BIT[15:14] is 'b00 Synopsys STAR 9001202023: Wrong microframe number for isochronous IN endpoints. Signed-off-by: Thinh Nguyen <thinhn@synopsys.com> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com> |
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| README | ||
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.