[U-Boot-Users] [PATCH 04/10 v2] [ARM] TQMA31: add new board with i.MX31 processor
Sascha Hauer
s.hauer at pengutronix.de
Thu Jul 10 12:16:35 CEST 2008
On Thu, Jul 10, 2008 at 11:46:45AM +0200, Wolfgang Denk wrote:
> In message <20080710093001.GR4595 at pengutronix.de> you wrote:
> >
> > How about using the Linux clocksource framework for U-Boot? I did this
>
> I have to admit that I don't know how big that code is?
Somewhere next to nothing:
/*
* clock.c - generic clocksource implementation
*
* This file contains the clocksource implementation from the Linux
* kernel originally by John Stultz
*
* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul at us.ibm.com)
* Copyright (c) 2007 Sascha Hauer <s.hauer at pengutronix.de>, Pengutronix
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <common.h>
#include <asm-generic/div64.h>
#include <clock.h>
static struct clocksource *current_clock;
static uint64_t time_ns;
/**
* get_time_ns - get current timestamp in nanoseconds
*/
uint64_t get_time_ns(void)
{
struct clocksource *cs = current_clock;
uint64_t cycle_now, cycle_delta;
uint64_t ns_offset;
/* read clocksource: */
cycle_now = cs->read();
/* calculate the delta since the last call: */
cycle_delta = (cycle_now - cs->cycle_last) & cs->mask;
/* convert to nanoseconds: */
ns_offset = cyc2ns(cs, cycle_delta);
cs->cycle_last = cycle_now;
time_ns += ns_offset;
return time_ns;
}
EXPORT_SYMBOL(get_time_ns);
/**
* clocksource_hz2mult - calculates mult from hz and shift
* @hz: Clocksource frequency in Hz
* @shift_constant: Clocksource shift factor
*
* Helper functions that converts a hz counter
* frequency to a timsource multiplier, given the
* clocksource shift value
*/
uint32_t clocksource_hz2mult(uint32_t hz, uint32_t shift_constant)
{
/* hz = cyc/(Billion ns)
* mult/2^shift = ns/cyc
* mult = ns/cyc * 2^shift
* mult = 1Billion/hz * 2^shift
* mult = 1000000000 * 2^shift / hz
* mult = (1000000000<<shift) / hz
*/
uint64_t tmp = ((uint64_t)1000000000) << shift_constant;
tmp += hz/2; /* round for do_div */
do_div(tmp, hz);
return (uint32_t)tmp;
}
int is_timeout(uint64_t start_ns, uint64_t time_offset_ns)
{
if (start_ns + time_offset_ns < get_time_ns())
return 1;
else
return 0;
}
EXPORT_SYMBOL(is_timeout);
void udelay(unsigned long usecs)
{
uint64_t start = get_time_ns();
while(!is_timeout(start, usecs * 1000));
}
EXPORT_SYMBOL(udelay);
void mdelay(unsigned long msecs)
{
uint64_t start = get_time_ns();
while(!is_timeout(start, msecs * 1000000));
}
EXPORT_SYMBOL(mdelay);
int init_clock(struct clocksource *cs)
{
current_clock = cs;
return 0;
}
The clocksource driver itself adds another 100 lines of code (for mx31).
The implementation of udelay shows how to implement timeouts, the main
usage of timing functions.
Regards,
Sascha
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