xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

ARM: 7205/2: sched_clock: allow sched_clock to be selected at runtime

Browse Source 
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>
This commit is contained in:
Marc Zyngier
2011-12-15 12:19:23 +01:00
committed by Russell King
parent 3bdc3484e8
commit 2f0778afac
19 changed files with 161 additions and 435 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
arch/arm/mach-tegra/timer.c
View File

@@ -19,7 +19,6 @@
#include <linux/init.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
@@ -106,25 +105,9 @@ static struct clock_event_device tegra_clockevent = {
.set_mode = tegra_timer_set_mode,
};
static DEFINE_CLOCK_DATA(cd);
/*
* Constants generated by clocks_calc_mult_shift(m, s, 1MHz, NSEC_PER_SEC, 60).
* This gives a resolution of about 1us and a wrap period of about 1h11min.
*/
#define SC_MULT 4194304000u
#define SC_SHIFT 22
unsigned long long notrace sched_clock(void)
static u32 notrace tegra_read_sched_clock(void)
{
u32 cyc = timer_readl(TIMERUS_CNTR_1US);
return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
}
static void notrace tegra_update_sched_clock(void)
{
u32 cyc = timer_readl(TIMERUS_CNTR_1US);
update_sched_clock(&cd, cyc, (u32)~0);
return timer_readl(TIMERUS_CNTR_1US);
}
/*
@@ -218,8 +201,7 @@ static void __init tegra_init_timer(void)
WARN(1, "Unknown clock rate");
}
init_fixed_sched_clock(&cd, tegra_update_sched_clock, 32,
1000000, SC_MULT, SC_SHIFT);
setup_sched_clock(tegra_read_sched_clock, 32, 1000000);
if (clocksource_mmio_init(timer_reg_base + TIMERUS_CNTR_1US,
"timer_us", 1000000, 300, 32, clocksource_mmio_readl_up)) {