coreboot-kgpe-d16/payloads/libpayload
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
..
arch libpayload arm64: Add gdb stub for arm64 2015-01-09 07:08:08 +01:00
bin libpayload: Add support for arm64 in libpayload 2015-01-09 07:04:28 +01:00
configs libpayload: Add Rock Chip drivers 2015-01-12 05:55:30 +01:00
crypto
curses libpayload/PDcurses: avoid NULL deref 2015-01-03 23:58:22 +01:00
drivers libpayload: Add Rock Chip drivers 2015-01-12 05:55:30 +01:00
gdb libpayload: Add remote GDB support 2015-01-09 07:06:51 +01:00
include libpayload arm64: Correct function names for tlb invalidation 2015-01-09 07:07:27 +01:00
libc libpayload: improve us timer accuracy 2015-01-12 05:55:45 +01:00
libcbfs libpayload: Fix pointer related casts 2014-12-31 18:57:35 +01:00
liblzma
libpci
sample
tests
util libpayload: Add support for arm64 in libpayload 2015-01-09 07:04:28 +01:00
Config.in libpayload: Add Rock Chip drivers 2015-01-12 05:55:30 +01:00
Doxyfile
LICENSES libpayload: Introduce new Kconfig to explicitly allow GPL code 2015-01-09 07:06:27 +01:00
LICENSE_GPL libpayload: Introduce new Kconfig to explicitly allow GPL code 2015-01-09 07:06:27 +01:00
Makefile libpayload: Add support for arm64 in libpayload 2015-01-09 07:04:28 +01:00
Makefile.inc libpayload: Add remote GDB support 2015-01-09 07:06:51 +01:00
README

README

-------------------------------------------------------------------------------
libpayload README
-------------------------------------------------------------------------------

libpayload is a minimal library to support standalone payloads
that can be booted with firmware like coreboot. It handles the setup
code, and provides common C library symbols such as malloc() and printf().

Note: This is _not_ a standard library for use with an operating system,
rather it's only useful for coreboot payload development!
See http://coreboot.org for details on coreboot.


Installation
------------

 $ git clone http://review.coreboot.org/p/coreboot.git

 $ cd coreboot/payloads/libpayload

 $ make menuconfig

 $ make

 $ sudo make install (optional, will install into /opt per default)

As libpayload is for 32bit x86 systems only, you might have to install the
32bit libgcc version, otherwise your payloads will fail to compile.
On Debian systems you'd do 'apt-get install gcc-multilib' for example.


Usage
-----

Here's an example of a very simple payload (hello.c) and how to build it:

 #include <libpayload.h>

 int main(void)
 {
     printf("Hello, world!\n");
     return 0;
 }

Building the payload using the 'lpgcc' compiler wrapper:

 $ lpgcc -o hello.elf hello.c

Please see the sample/ directory for details.


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

The main website is http://www.coreboot.org/Libpayload.

For additional information, patches, and discussions, please join the
coreboot mailing list at http://coreboot.org/Mailinglist, where most
libpayload developers are subscribed.


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

See LICENSES.