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, 4 insertions, 54 deletions

diff --git a/arch/arm/mach-omap1/time.c b/arch/arm/mach-omap1/time.c
index 485a21d31004..b8faffa44f9e 100644
--- a/arch/arm/mach-omap1/time.c
+++ b/arch/arm/mach-omap1/time.c
@@ -37,7 +37,6 @@
 #include <linux/init.h>
 #include <linux/delay.h>
 #include <linux/interrupt.h>
-#include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/clk.h>
 #include <linux/err.h>
@@ -190,30 +189,9 @@ static __init void omap_init_mpu_timer(unsigned long rate)
  * ---------------------------------------------------------------------------
  */
 
-static DEFINE_CLOCK_DATA(cd);
-
-static inline unsigned long long notrace _omap_mpu_sched_clock(void)
-{
-        u32 cyc = ~omap_mpu_timer_read(1);
-        return cyc_to_sched_clock(&cd, cyc, (u32)~0);
-}
-
-#ifndef CONFIG_OMAP_32K_TIMER
-unsigned long long notrace sched_clock(void)
-{
-        return _omap_mpu_sched_clock();
-}
-#else
-static unsigned long long notrace omap_mpu_sched_clock(void)
-{
-        return _omap_mpu_sched_clock();
-}
-#endif
-
-static void notrace mpu_update_sched_clock(void)
+static u32 notrace omap_mpu_read_sched_clock(void)
 {
-        u32 cyc = ~omap_mpu_timer_read(1);
-        update_sched_clock(&cd, cyc, (u32)~0);
+        return ~omap_mpu_timer_read(1);
 }
 
 static void __init omap_init_clocksource(unsigned long rate)
@@ -223,7 +201,7 @@ static void __init omap_init_clocksource(unsigned long rate)
                         "%s: can't register clocksource!\n";
 
         omap_mpu_timer_start(1, ~0, 1);
-        init_sched_clock(&cd, mpu_update_sched_clock, 32, rate);
+        setup_sched_clock(omap_mpu_read_sched_clock, 32, rate);
 
         if (clocksource_mmio_init(&timer->read_tim, "mpu_timer2", rate,
                         300, 32, clocksource_mmio_readl_down))
@@ -254,30 +232,6 @@ static inline void omap_mpu_timer_init(void)
 }
 #endif  /* CONFIG_OMAP_MPU_TIMER */
 
-#if defined(CONFIG_OMAP_MPU_TIMER) && defined(CONFIG_OMAP_32K_TIMER)
-static unsigned long long (*preferred_sched_clock)(void);
-
-unsigned long long notrace sched_clock(void)
-{
-        if (!preferred_sched_clock)
-                return 0;
-
-        return preferred_sched_clock();
-}
-
-static inline void preferred_sched_clock_init(bool use_32k_sched_clock)
-{
-        if (use_32k_sched_clock)
-                preferred_sched_clock = omap_32k_sched_clock;
-        else
-                preferred_sched_clock = omap_mpu_sched_clock;
-}
-#else
-static inline void preferred_sched_clock_init(bool use_32k_sched_clcok)
-{
-}
-#endif
-
 static inline int omap_32k_timer_usable(void)
 {
         int res = false;
@@ -299,12 +253,8 @@ static inline int omap_32k_timer_usable(void)
  */
 static void __init omap1_timer_init(void)
 {
-        if (omap_32k_timer_usable()) {
-                preferred_sched_clock_init(1);
-        } else {
+        if (!omap_32k_timer_usable())
                 omap_mpu_timer_init();
-                preferred_sched_clock_init(0);
-        }
 }
 
 struct sys_timer omap1_timer = {