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timestamp: Add function to get time since boot

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Add a function to retrieve the elapsed time since boot. For that purpose
use the base time in the timestamp table among with the current
timestamp at call time of the function. So more precise the returned
time is the elapsed time since the timestamp was initialized scaled
in microseconds. This was chosen to get a reliable value even on
platforms where the TSC might not be reset on software reset or warm
start.

Change-Id: Ib93ad89078645c0ebe256048cb48f9622c90451f
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/21516
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
This commit is contained in:
Werner Zeh 2017-09-12 07:42:54 +02:00
parent 653f019d0d
commit 35cceb861c
2 changed files with 24 additions and 0 deletions
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10
src/include/timestamp.h
View file

@ -2,6 +2,7 @@
* This file is part of the coreboot project.
*
* Copyright (C) 2011 The ChromiumOS Authors. All rights reserved.
* Copyright 2017 Siemens AG.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -40,11 +41,20 @@ void timestamp_add_now(enum timestamp_id id);
/* Apply a factor of N/M to all timestamps recorded so far. */
void timestamp_rescale_table(uint16_t N, uint16_t M);
/*
* Get the time since boot scaled in microseconds. Therefore use the base time
* of the timestamps to get the initial value which is subtracted from
* current timestamp at call time. This will provide a more reliable value even
* if the TSC is not reset on soft reset or warm start.
*/
uint32_t get_us_since_boot(void);
#else
#define timestamp_init(base)
#define timestamp_add(id, time)
#define timestamp_add_now(id)
#define timestamp_rescale_table(N, M)
#define get_us_since_boot() 0
#endif
/* Implemented by the architecture code */

14
src/lib/timestamp.c
View file

@ -2,6 +2,7 @@
* This file is part of the coreboot project.
*
* Copyright (C) 2011 The ChromiumOS Authors. All rights reserved.
* Copyright 2017 Siemens AG.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -327,6 +328,19 @@ void timestamp_rescale_table(uint16_t N, uint16_t M)
}
}
/*
* Get the time in microseconds since boot (or more precise: since timestamp
* table was initialized).
*/
uint32_t get_us_since_boot(void)
{
struct timestamp_table *ts = timestamp_table_get();
if (ts == NULL || ts->tick_freq_mhz == 0)
return 0;
return (timestamp_get() - ts->base_time) / ts->tick_freq_mhz;
}
ROMSTAGE_CBMEM_INIT_HOOK(timestamp_sync_cache_to_cbmem)
RAMSTAGE_CBMEM_INIT_HOOK(timestamp_sync_cache_to_cbmem)