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Vadim Bendebury 1c5cdad09e libpayload: improve us timer accuracy
In cases where timer clock frequency is not an integer number of
megahertz, the calculations in timer_us() lack accuracy.

This patch modifies calculations to reduce the error. The maximum
interval this calculation would support decreases, but it still is in
excess of 1844674 seconds for a timer clocked by 10 MHz, which is more
than enough.

BUG=none
TEST=manual
  . verified timer accuracy using a depthcharge CLI command

Original-Change-Id: Iffb323db10e74b0ce3b4d59a56983bfee12e6805
Original-Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/207358
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
(cherry picked from commit e1abf87d438de1a04714482d5b610671e8cc0663)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Ia892726187ab040dd235f493c92856c15951cc06
Reviewed-on: http://review.coreboot.org/8128
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins)
2015-01-12 05:55:45 +01:00
3rdparty@a8b0c52850 3rdparty: Update to latest commit in blobs repository 2014-12-28 16:04:03 +01:00
documentation Doxygen: add a "simple" output config and make target 2015-01-08 21:59:17 +01:00
payloads libpayload: improve us timer accuracy 2015-01-12 05:55:45 +01:00
src mainboard/lenovo/x201/romstage.c: Remove unused function 2015-01-11 08:28:31 +01:00
util cbfstool: Fix help display message 2015-01-09 07:49:53 +01:00
.gitignore .gitignore: add the doxygen directory. 2014-12-14 23:30:45 +01:00
.gitmodules nvidia/cbootimage: avoid upstream's build system 2014-10-02 10:26:58 +02:00
.gitreview
COPYING
Makefile Doxygen: add a "simple" output config and make target 2015-01-08 21:59:17 +01:00
Makefile.inc intel: Fix UPDATE-FIT step in build 2014-12-28 19:58:59 +01:00
README
toolchain.inc Set custom AR_ for each class 2015-01-09 07:49:14 +01:00

README

-------------------------------------------------------------------------------
coreboot README
-------------------------------------------------------------------------------

coreboot is a Free Software project aimed at replacing the proprietary BIOS
(firmware) found in most computers.  coreboot performs a little bit of
hardware initialization and then executes additional boot logic, called a
payload.

With the separation of hardware initialization and later boot logic,
coreboot can scale from specialized applications that run directly
firmware, run operating systems in flash, load custom
bootloaders, or implement firmware standards, like PC BIOS services or
UEFI. This allows for systems to only include the features necessary
in the target application, reducing the amount of code and flash space
required.

coreboot was formerly known as LinuxBIOS.


Payloads
--------

After the basic initialization of the hardware has been performed, any
desired "payload" can be started by coreboot.

See http://www.coreboot.org/Payloads for a list of supported payloads.


Supported Hardware
------------------

coreboot supports a wide range of chipsets, devices, and mainboards.

For details please consult:

 * http://www.coreboot.org/Supported_Motherboards
 * http://www.coreboot.org/Supported_Chipsets_and_Devices


Build Requirements
------------------

 * gcc / g++
 * make

Optional:

 * doxygen (for generating/viewing documentation)
 * iasl (for targets with ACPI support)
 * gdb (for better debugging facilities on some targets)
 * ncurses (for 'make menuconfig')
 * flex and bison (for regenerating parsers)


Building coreboot
-----------------

Please consult http://www.coreboot.org/Build_HOWTO for details.


Testing coreboot Without Modifying Your Hardware
------------------------------------------------

If you want to test coreboot without any risks before you really decide
to use it on your hardware, you can use the QEMU system emulator to run
coreboot virtually in QEMU.

Please see http://www.coreboot.org/QEMU for details.


Website and Mailing List
------------------------

Further details on the project, a FAQ, many HOWTOs, news, development
guidelines and more can be found on the coreboot website:

  http://www.coreboot.org

You can contact us directly on the coreboot mailing list:

  http://www.coreboot.org/Mailinglist


Copyright and License
---------------------

The copyright on coreboot is owned by quite a large number of individual
developers and companies. Please check the individual source files for details.

coreboot is licensed under the terms of the GNU General Public License (GPL).
Some files are licensed under the "GPL (version 2, or any later version)",
and some files are licensed under the "GPL, version 2". For some parts, which
were derived from other projects, other (GPL-compatible) licenses may apply.
Please check the individual source files for details.

This makes the resulting coreboot images licensed under the GPL, version 2.