linux/arch/arm/plat-omap/counter_32k.c
Marc Zyngier 2f0778afac ARM: 7205/2: sched_clock: allow sched_clock to be selected at runtime
sched_clock() is yet another blocker on the road to the single
image. This patch implements an idea by Russell King:

http://www.spinics.net/lists/linux-omap/msg49561.html

Instead of asking the platform to implement both sched_clock()
itself and the rollover callback, simply register a read()
function, and let the ARM code care about sched_clock() itself,
the conversion to ns and the rollover. sched_clock() uses
this read() function as an indirection to the platform code.
If the platform doesn't provide a read(), the code falls back
to the jiffy counter (just like the default sched_clock).

This allow some simplifications and possibly some footprint gain
when multiple platforms are compiled in. Among the drawbacks,
the removal of the *_fixed_sched_clock optimization which could
negatively impact some platforms (sa1100, tegra, versatile
and omap).

Tested on 11MPCore, OMAP4 and Tegra.

Cc: Imre Kaloz <kaloz@openwrt.org>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Colin Cross <ccross@android.com>
Cc: Erik Gilling <konkers@android.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Alessandro Rubini <rubini@unipv.it>
Cc: STEricsson <STEricsson_nomadik_linux@list.st.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Ben Dooks <ben-linux@fluff.org>
Tested-by: Jamie Iles <jamie@jamieiles.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Krzysztof Halasa <khc@pm.waw.pl>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-12-18 23:00:26 +00:00

121 lines
3.3 KiB
C

/*
* OMAP 32ksynctimer/counter_32k-related code
*
* Copyright (C) 2009 Texas Instruments
* Copyright (C) 2010 Nokia Corporation
* Tony Lindgren <tony@atomide.com>
* Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
*
* 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.
*
* NOTE: This timer is not the same timer as the old OMAP1 MPU timer.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/clocksource.h>
#include <asm/sched_clock.h>
#include <plat/common.h>
#include <plat/board.h>
#include <plat/clock.h>
/*
* 32KHz clocksource ... always available, on pretty most chips except
* OMAP 730 and 1510. Other timers could be used as clocksources, with
* higher resolution in free-running counter modes (e.g. 12 MHz xtal),
* but systems won't necessarily want to spend resources that way.
*/
static void __iomem *timer_32k_base;
#define OMAP16XX_TIMER_32K_SYNCHRONIZED 0xfffbc410
static u32 notrace omap_32k_read_sched_clock(void)
{
return timer_32k_base ? __raw_readl(timer_32k_base) : 0;
}
/**
* read_persistent_clock - Return time from a persistent clock.
*
* Reads the time from a source which isn't disabled during PM, the
* 32k sync timer. Convert the cycles elapsed since last read into
* nsecs and adds to a monotonically increasing timespec.
*/
static struct timespec persistent_ts;
static cycles_t cycles, last_cycles;
static unsigned int persistent_mult, persistent_shift;
void read_persistent_clock(struct timespec *ts)
{
unsigned long long nsecs;
cycles_t delta;
struct timespec *tsp = &persistent_ts;
last_cycles = cycles;
cycles = timer_32k_base ? __raw_readl(timer_32k_base) : 0;
delta = cycles - last_cycles;
nsecs = clocksource_cyc2ns(delta, persistent_mult, persistent_shift);
timespec_add_ns(tsp, nsecs);
*ts = *tsp;
}
int __init omap_init_clocksource_32k(void)
{
static char err[] __initdata = KERN_ERR
"%s: can't register clocksource!\n";
if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
u32 pbase;
unsigned long size = SZ_4K;
void __iomem *base;
struct clk *sync_32k_ick;
if (cpu_is_omap16xx()) {
pbase = OMAP16XX_TIMER_32K_SYNCHRONIZED;
size = SZ_1K;
} else if (cpu_is_omap2420())
pbase = OMAP2420_32KSYNCT_BASE + 0x10;
else if (cpu_is_omap2430())
pbase = OMAP2430_32KSYNCT_BASE + 0x10;
else if (cpu_is_omap34xx())
pbase = OMAP3430_32KSYNCT_BASE + 0x10;
else if (cpu_is_omap44xx())
pbase = OMAP4430_32KSYNCT_BASE + 0x10;
else
return -ENODEV;
/* For this to work we must have a static mapping in io.c for this area */
base = ioremap(pbase, size);
if (!base)
return -ENODEV;
sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
if (!IS_ERR(sync_32k_ick))
clk_enable(sync_32k_ick);
timer_32k_base = base;
/*
* 120000 rough estimate from the calculations in
* __clocksource_updatefreq_scale.
*/
clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
32768, NSEC_PER_SEC, 120000);
if (clocksource_mmio_init(base, "32k_counter", 32768, 250, 32,
clocksource_mmio_readl_up))
printk(err, "32k_counter");
setup_sched_clock(omap_32k_read_sched_clock, 32, 32768);
}
return 0;
}