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With write-allocate cache we get into the following scenario: 1. data has been updated in the memory by the USB HC, but 2. D-cache holds an un-flushed value of it 3. when affected cache line is being replaced, the old (un-flushed) value is flushed and overwrites the newly arrived This is possible due to how write-allocate works with virtual caches (ARM for example). In case of USB transfers it leads to fatal tags discrepancies in umass(4) operation, which look like the following: umass0: Invalid CSW: tag 1 should be 2 (probe0:umass-sim0:0:0:0): Request completed with CAM_REQ_CMP_ERR (probe0:umass-sim0:0:0:0): Retrying Command umass0: Invalid CSW: tag 1 should be 3 (probe0:umass-sim0:0:0:0): Request completed with CAM_REQ_CMP_ERR (probe0:umass-sim0:0:0:0): Retrying Command umass0: Invalid CSW: tag 1 should be 4 (probe0:umass-sim0:0:0:0): Request completed with CAM_REQ_CMP_ERR (probe0:umass-sim0:0:0:0): Retrying Command umass0: Invalid CSW: tag 1 should be 5 (probe0:umass-sim0:0:0:0): Request completed with CAM_REQ_CMP_ERR (probe0:umass-sim0:0:0:0): Retrying Command umass0: Invalid CSW: tag 1 should be 6 (probe0:umass-sim0:0:0:0): Request completed with CAM_REQ_CMP_ERR (probe0:umass-sim0:0:0:0): error 5 (probe0:umass-sim0:0:0:0): Retries Exausted To eliminate this, a BUS_DMASYNC_PREREAD sync operation is required in usbd_start_transfer(). Credits for nailing this down go to Grzegorz Bernacki gjb AT semihalf DOT com. Reviewed by: imp Approved by: cognet (mentor) |
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| bin | ||
| cddl | ||
| compat/opensolaris | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| ObsoleteFiles.inc | ||
| README | ||
| UPDATING | ||
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``world'' target should only be used in cases where the source tree has not changed from the currently running version. See: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. rescue Build system for statically linked /rescue utilities. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html