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clocksource: add dummy software-only clocksource 

This driver is very handy for initial barebox porting.
It was used for running barebox on DiGiC2-based camera
and initial porting barebox to Loongson-1 and ar9331.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Reported-by: Alexander Aring <alex.aring@gmail.com>
Reported-by: Alexander Shiyan <shc_work@mail.ru>
This commit is contained in:
Antony Pavlov 2014-03-17 13:37:02 +04:00 committed by Sascha Hauer
parent 5a6410edd7
commit e6bbe60a53
3 changed files with 80 additions and 0 deletions
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23
drivers/clocksource/Kconfig
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@ -14,6 +14,29 @@ config CLOCKSOURCE_CLPS711X
bool
depends on ARCH_CLPS711X
config CLOCKSOURCE_DUMMY
bool "Enable dummy software-only clocksource"
help
When porting barebox to a new SoC there might be a case
of broken or absent clocksource. This causes barebox serial
console to be non functional.
To solve the problem this software-only clocksource driver is used.
WARNING!!! This clocksource doesn't provide correct timing.
To adjust this clocksource please use CONFIG_CLOCKSOURCE_DUMMY_RATE.
The bigger rate valuest makes clocksource "faster".
It's possible to add this clocksource unconditionally.
This clocksource starts very early (pure_initcall) so
real clocksource will take over.
This can help if initialization order is wrong so that
the time functions are used before the real clocksource
was initialized.
config CLOCKSOURCE_DUMMY_RATE
int
prompt "dummy clocksource rate"
depends on CLOCKSOURCE_DUMMY
default 1000
config CLOCKSOURCE_MVEBU
bool
depends on ARCH_MVEBU

1
drivers/clocksource/Makefile
View File

@ -2,6 +2,7 @@ obj-$(CONFIG_AMBA_SP804) += amba-sp804.o
obj-$(CONFIG_ARM_SMP_TWD) += arm_smp_twd.o
obj-$(CONFIG_CLOCKSOURCE_BCM2835) += bcm2835.o
obj-$(CONFIG_CLOCKSOURCE_CLPS711X) += clps711x.o
obj-$(CONFIG_CLOCKSOURCE_DUMMY) += dummy.o
obj-$(CONFIG_CLOCKSOURCE_MVEBU) += mvebu.o
obj-$(CONFIG_CLOCKSOURCE_NOMADIK) += nomadik.o
obj-$(CONFIG_CLOCKSOURCE_ORION) += orion.o

56
drivers/clocksource/dummy.c Normal file
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@ -0,0 +1,56 @@
/*
* Copyright (C) 2013 Antony Pavlov <antonynpavlov@gmail.com>
*
* This file is part of barebox.
* See file CREDITS for list of people who contributed to this project.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/
#include <common.h>
#include <init.h>
#include <clock.h>
static uint64_t dummy_counter;
static uint64_t dummy_cs_read(void)
{
static int first;
if (!first) {
pr_warn("Warning: Using dummy clocksource\n");
first = 1;
}
dummy_counter += CONFIG_CLOCKSOURCE_DUMMY_RATE;
return dummy_counter;
}
static struct clocksource dummy_cs = {
.read = dummy_cs_read,
.mask = CLOCKSOURCE_MASK(32),
};
static int clocksource_init(void)
{
dummy_counter = 0;
clocks_calc_mult_shift(&dummy_cs.mult, &dummy_cs.shift,
100000000, NSEC_PER_SEC, 10);
pr_debug("clocksource_init: mult=%08x, shift=%08x\n",
dummy_cs.mult, dummy_cs.shift);
init_clock(&dummy_cs);
return 0;
}
pure_initcall(clocksource_init);