diff options
author | Marc Zyngier <Marc.Zyngier@arm.com> | 2011-12-15 12:19:23 +0100 |
---|---|---|
committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2011-12-18 23:00:26 +0000 |
commit | 2f0778afac79bd8d226225556858a636931eeabc (patch) | |
tree | e00cea674f3d6cc8c5584aa5b75239f11f6d229d /arch/arm/mach-sa1100 | |
parent | 3bdc3484e8f2b1b219ad0397d81ce4601fbaf76d (diff) | |
download | linux-2f0778afac79bd8d226225556858a636931eeabc.tar.bz2 |
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>
Diffstat (limited to 'arch/arm/mach-sa1100')
-rw-r--r-- | arch/arm/mach-sa1100/time.c | 28 |
1 files changed, 3 insertions, 25 deletions
diff --git a/arch/arm/mach-sa1100/time.c b/arch/arm/mach-sa1100/time.c index fa6602491d54..1ee6d4ca8dd7 100644 --- a/arch/arm/mach-sa1100/time.c +++ b/arch/arm/mach-sa1100/time.c @@ -12,7 +12,6 @@ #include <linux/errno.h> #include <linux/interrupt.h> #include <linux/irq.h> -#include <linux/sched.h> /* just for sched_clock() - funny that */ #include <linux/timex.h> #include <linux/clockchips.h> @@ -20,29 +19,9 @@ #include <asm/sched_clock.h> #include <mach/hardware.h> -/* - * This is the SA11x0 sched_clock implementation. - */ -static DEFINE_CLOCK_DATA(cd); - -/* - * Constants generated by clocks_calc_mult_shift(m, s, 3.6864MHz, - * NSEC_PER_SEC, 60). - * This gives a resolution of about 271ns and a wrap period of about 19min. - */ -#define SC_MULT 2275555556u -#define SC_SHIFT 23 - -unsigned long long notrace sched_clock(void) -{ - u32 cyc = OSCR; - return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT); -} - -static void notrace sa1100_update_sched_clock(void) +static u32 notrace sa100_read_sched_clock(void) { - u32 cyc = OSCR; - update_sched_clock(&cd, cyc, (u32)~0); + return OSCR; } #define MIN_OSCR_DELTA 2 @@ -109,8 +88,7 @@ static void __init sa1100_timer_init(void) OIER = 0; OSSR = OSSR_M0 | OSSR_M1 | OSSR_M2 | OSSR_M3; - init_fixed_sched_clock(&cd, sa1100_update_sched_clock, 32, - 3686400, SC_MULT, SC_SHIFT); + setup_sched_clock(sa1100_read_sched_clock, 32, 3686400); clockevents_calc_mult_shift(&ckevt_sa1100_osmr0, 3686400, 4); ckevt_sa1100_osmr0.max_delta_ns = |