[coreboot-gerrit] New patch to review for coreboot: 1fae97e libpayload: improve us timer accuracy

[Marc Jones]

Marc Jones ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/8128

-gerrit

commit 1fae97eec67c0b01eb3a0523ae5b8872d5213c07
Author: Vadim Bendebury 
Date:   Thu Jul 10 12:49:46 2014 -0700

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 
    Original-Reviewed-on: https://chromium-review.googlesource.com/207358
    Original-Reviewed-by: David Hendricks 
    (cherry picked from commit e1abf87d438de1a04714482d5b610671e8cc0663)
    Signed-off-by: Marc Jones

Change-Id: Ia892726187ab040dd235f493c92856c15951cc06
---
 payloads/libpayload/libc/time.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/payloads/libpayload/libc/time.c b/payloads/libpayload/libc/time.c
index 0d81634..8d07c4f 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;
 }