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authorVadim Bendebury <vbendeb@chromium.org>2014-07-10 12:49:46 -0700
committerMarc Jones <marc.jones@se-eng.com>2015-01-12 05:55:45 +0100
commit1c5cdad09efa7d6bd196ad852dbeb5f740ac66e3 (patch)
treeb122e84cdc7be7918cc41021913a3ce0d30691cc /payloads/libpayload
parentab699846018d5a697d9d2c3f88031d932cc5fe58 (diff)
downloadcoreboot-1c5cdad09efa7d6bd196ad852dbeb5f740ac66e3.tar.xz
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)
Diffstat (limited to 'payloads/libpayload')
-rw-r--r--payloads/libpayload/libc/time.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/payloads/libpayload/libc/time.c b/payloads/libpayload/libc/time.c
index 0d8163495b..8d07c4f172 100644
--- a/payloads/libpayload/libc/time.c
+++ b/payloads/libpayload/libc/time.c
@@ -204,5 +204,5 @@ u64 timer_us(u64 base)
}
}
- return timer_raw_value() / (hz / 1000000) - base;
+ return (1000000 * timer_raw_value()) / hz - base;
}