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 <[email protected]>
Cc: Eric Miao <[email protected]>
Cc: Colin Cross <[email protected]>
Cc: Erik Gilling <[email protected]>
Cc: Olof Johansson <[email protected]>
Cc: Sascha Hauer <[email protected]>
Cc: Alessandro Rubini <[email protected]>
Cc: STEricsson <[email protected]>
Cc: Lennert Buytenhek <[email protected]>
Cc: Ben Dooks <[email protected]>
Tested-by: Jamie Iles <[email protected]>
Tested-by: Tony Lindgren <[email protected]>
Tested-by: Kyungmin Park <[email protected]>
Acked-by: Linus Walleij <[email protected]>
Acked-by: Nicolas Pitre <[email protected]>
Acked-by: Krzysztof Halasa <[email protected]>
Acked-by: Kukjin Kim <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Signed-off-by: Russell King <[email protected]>

1 files changed, 3 insertions, 13 deletions

diff --git a/arch/arm/mach-mmp/time.c b/arch/arm/mach-mmp/time.c
index 4e91ee6e27c8..71fc4ee4602c 100644
--- a/arch/arm/mach-mmp/time.c
+++ b/arch/arm/mach-mmp/time.c
@@ -25,7 +25,6 @@
 
 #include <linux/io.h>
 #include <linux/irq.h>
-#include <linux/sched.h>
 
 #include <asm/sched_clock.h>
 #include <mach/addr-map.h>
@@ -42,8 +41,6 @@
 #define MAX_DELTA		(0xfffffffe)
 #define MIN_DELTA		(16)
 
-static DEFINE_CLOCK_DATA(cd);
-
 /*
  * FIXME: the timer needs some delay to stablize the counter capture
  */
@@ -59,16 +56,9 @@ static inline uint32_t timer_read(void)
 	return __raw_readl(TIMERS_VIRT_BASE + TMR_CVWR(1));
 }
 
-unsigned long long notrace sched_clock(void)
+static u32 notrace mmp_read_sched_clock(void)
 {
-	u32 cyc = timer_read();
-	return cyc_to_sched_clock(&cd, cyc, (u32)~0);
-}
-
-static void notrace mmp_update_sched_clock(void)
-{
-	u32 cyc = timer_read();
-	update_sched_clock(&cd, cyc, (u32)~0);
+	return timer_read();
 }
 
 static irqreturn_t timer_interrupt(int irq, void *dev_id)
@@ -201,7 +191,7 @@ void __init timer_init(int irq)
 {
 	timer_config();
 
-	init_sched_clock(&cd, mmp_update_sched_clock, 32, CLOCK_TICK_RATE);
+	setup_sched_clock(mmp_read_sched_clock, 32, CLOCK_TICK_RATE);
 
 	ckevt.mult = div_sc(CLOCK_TICK_RATE, NSEC_PER_SEC, ckevt.shift);
 	ckevt.max_delta_ns = clockevent_delta2ns(MAX_DELTA, &ckevt);