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>
diff --git a/arch/arm/plat-versatile/sched-clock.c b/arch/arm/plat-versatile/sched-clock.c
index 3d6a4c2..b33b74c 100644
--- a/arch/arm/plat-versatile/sched-clock.c
+++ b/arch/arm/plat-versatile/sched-clock.c
@@ -18,41 +18,24 @@
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
+#include <linux/kernel.h>
#include <linux/io.h>
-#include <linux/sched.h>
#include <asm/sched_clock.h>
#include <plat/sched_clock.h>
-static DEFINE_CLOCK_DATA(cd);
static void __iomem *ctr;
-/*
- * Constants generated by clocks_calc_mult_shift(m, s, 24MHz, NSEC_PER_SEC, 60).
- * This gives a resolution of about 41ns and a wrap period of about 178s.
- */
-#define SC_MULT 2796202667u
-#define SC_SHIFT 26
-
-unsigned long long notrace sched_clock(void)
+static u32 notrace versatile_read_sched_clock(void)
{
- if (ctr) {
- u32 cyc = readl(ctr);
- return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0,
- SC_MULT, SC_SHIFT);
- } else
- return 0;
-}
+ if (ctr)
+ return readl(ctr);
-static void notrace versatile_update_sched_clock(void)
-{
- u32 cyc = readl(ctr);
- update_sched_clock(&cd, cyc, (u32)~0);
+ return 0;
}
void __init versatile_sched_clock_init(void __iomem *reg, unsigned long rate)
{
ctr = reg;
- init_fixed_sched_clock(&cd, versatile_update_sched_clock,
- 32, rate, SC_MULT, SC_SHIFT);
+ setup_sched_clock(versatile_read_sched_clock, 32, rate);
}