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>

1 files changed, 3 insertions, 18 deletions

diff --git a/arch/arm/plat-orion/time.c b/arch/arm/plat-orion/time.c
index 69a6136..1ed8d13 100644
--- a/arch/arm/plat-orion/time.c
+++ b/arch/arm/plat-orion/time.c
@@ -12,7 +12,6 @@
  */
 
 #include <linux/kernel.h>
-#include <linux/sched.h>
 #include <linux/timer.h>
 #include <linux/clockchips.h>
 #include <linux/interrupt.h>
@@ -60,24 +59,10 @@ static u32 ticks_per_jiffy;
  * Orion's sched_clock implementation. It has a resolution of
  * at least 7.5ns (133MHz TCLK).
  */
-static DEFINE_CLOCK_DATA(cd);
 
-unsigned long long notrace sched_clock(void)
+static u32 notrace orion_read_sched_clock(void)
 {
-	u32 cyc = ~readl(timer_base + TIMER0_VAL_OFF);
-	return cyc_to_sched_clock(&cd, cyc, (u32)~0);
-}
-
-
-static void notrace orion_update_sched_clock(void)
-{
-	u32 cyc = ~readl(timer_base + TIMER0_VAL_OFF);
-	update_sched_clock(&cd, cyc, (u32)~0);
-}
-
-static void __init setup_sched_clock(unsigned long tclk)
-{
-	init_sched_clock(&cd, orion_update_sched_clock, 32, tclk);
+	return ~readl(timer_base + TIMER0_VAL_OFF);
 }
 
 /*
@@ -217,7 +202,7 @@ orion_time_init(u32 _bridge_base, u32 _bridge_timer1_clr_mask,
 	/*
 	 * Set scale and timer for sched_clock.
 	 */
-	setup_sched_clock(tclk);
+	setup_sched_clock(orion_read_sched_clock, 32, tclk);
 
 	/*
 	 * Setup free-running clocksource timer (interrupts