[PATCH] Use MMIO clocksource for 32kHz counter
Tony Lindgren
tony at atomide.com
Mon Jul 11 02:17:31 EDT 2011
* Russell King - ARM Linux <linux at arm.linux.org.uk> [110710 07:10]:
> On Mon, Jun 27, 2011 at 12:11:02PM -0700, Tony Lindgren wrote:
> > * Tony Lindgren <tony at atomide.com> [110627 05:33]:
> > > * Russell King - ARM Linux <linux at arm.linux.org.uk> [110627 05:28]:
> > > > --- a/arch/arm/plat-omap/counter_32k.c
> > > > +++ b/arch/arm/plat-omap/counter_32k.c
> > > > +#ifdef CONFIG_ARCH_OMAP16XX
> > > > + else if (cpu_is_omap16xx())
> > > > + base = OMAP2_L4_IO_ADDRESS(OMAP16XX_TIMER_32K_SYNCHRONIZED);
> >
> > BTW, the above should have been OMAP1_IO_ADDRESS instead..
> >
> > > You should be able to replace the above with just ioremap as we now
> > > have the static mappings.
> >
> > ..here's a patch to use ioremap with comment added about the static
> > mapping requirements.
> >
> > Thanks for getting rid of hopefully the last remaining omap_readl
> > for omap2+ BTW :)
>
> What're we doing with this patch and your follow-up patch?
I can queue it, it does not seem to conflict with other patches.
Below is the combined version.
Regards,
Tony
From: Russell King - ARM Linux <linux at arm.linux.org.uk>
Date: Sun, 10 Jul 2011 23:05:34 -0700
Subject: [PATCH] Convert OMAPs 32kHz clocksource implementation to use the generic MMIO
clocksource support. This achieves several things:
1. It means we get rid of all these helper functions which frankly should
never have been necessary.
2. It means omap_readl() inside these helper functions does not appear in
ftrace output.
Another plus is that we avoid the overhead of calculating the address to
read each time, but a minus is that we use readl() which has a barrier.
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
[tony at atomide.com: updated to use ioremap]
Signed-off-by: Tony Lindgren <tony at atomide.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 9adc278..c1795c9 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -852,6 +852,7 @@ config ARCH_OMAP
select HAVE_CLK
select ARCH_REQUIRE_GPIOLIB
select ARCH_HAS_CPUFREQ
+ select CLKSRC_MMIO
select GENERIC_CLOCKEVENTS
select HAVE_SCHED_CLOCK
select ARCH_HAS_HOLES_MEMORYMODEL
diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c
index c13bc3d..a6cbb71 100644
--- a/arch/arm/plat-omap/counter_32k.c
+++ b/arch/arm/plat-omap/counter_32k.c
@@ -18,6 +18,7 @@
#include <linux/err.h>
#include <linux/io.h>
#include <linux/sched.h>
+#include <linux/clocksource.h>
#include <asm/sched_clock.h>
@@ -26,87 +27,16 @@
#include <plat/clock.h>
-
/*
* 32KHz clocksource ... always available, on pretty most chips except
* OMAP 730 and 1510. Other timers could be used as clocksources, with
* higher resolution in free-running counter modes (e.g. 12 MHz xtal),
* but systems won't necessarily want to spend resources that way.
*/
+static void __iomem *timer_32k_base;
#define OMAP16XX_TIMER_32K_SYNCHRONIZED 0xfffbc410
-#include <linux/clocksource.h>
-
-/*
- * offset_32k holds the init time counter value. It is then subtracted
- * from every counter read to achieve a counter that counts time from the
- * kernel boot (needed for sched_clock()).
- */
-static u32 offset_32k __read_mostly;
-
-#ifdef CONFIG_ARCH_OMAP16XX
-static cycle_t notrace omap16xx_32k_read(struct clocksource *cs)
-{
- return omap_readl(OMAP16XX_TIMER_32K_SYNCHRONIZED) - offset_32k;
-}
-#else
-#define omap16xx_32k_read NULL
-#endif
-
-#ifdef CONFIG_SOC_OMAP2420
-static cycle_t notrace omap2420_32k_read(struct clocksource *cs)
-{
- return omap_readl(OMAP2420_32KSYNCT_BASE + 0x10) - offset_32k;
-}
-#else
-#define omap2420_32k_read NULL
-#endif
-
-#ifdef CONFIG_SOC_OMAP2430
-static cycle_t notrace omap2430_32k_read(struct clocksource *cs)
-{
- return omap_readl(OMAP2430_32KSYNCT_BASE + 0x10) - offset_32k;
-}
-#else
-#define omap2430_32k_read NULL
-#endif
-
-#ifdef CONFIG_ARCH_OMAP3
-static cycle_t notrace omap34xx_32k_read(struct clocksource *cs)
-{
- return omap_readl(OMAP3430_32KSYNCT_BASE + 0x10) - offset_32k;
-}
-#else
-#define omap34xx_32k_read NULL
-#endif
-
-#ifdef CONFIG_ARCH_OMAP4
-static cycle_t notrace omap44xx_32k_read(struct clocksource *cs)
-{
- return omap_readl(OMAP4430_32KSYNCT_BASE + 0x10) - offset_32k;
-}
-#else
-#define omap44xx_32k_read NULL
-#endif
-
-/*
- * Kernel assumes that sched_clock can be called early but may not have
- * things ready yet.
- */
-static cycle_t notrace omap_32k_read_dummy(struct clocksource *cs)
-{
- return 0;
-}
-
-static struct clocksource clocksource_32k = {
- .name = "32k_counter",
- .rating = 250,
- .read = omap_32k_read_dummy,
- .mask = CLOCKSOURCE_MASK(32),
- .flags = CLOCK_SOURCE_IS_CONTINUOUS,
-};
-
/*
* Returns current time from boot in nsecs. It's OK for this to wrap
* around for now, as it's just a relative time stamp.
@@ -122,7 +52,7 @@ static DEFINE_CLOCK_DATA(cd);
static inline unsigned long long notrace _omap_32k_sched_clock(void)
{
- u32 cyc = clocksource_32k.read(&clocksource_32k);
+ u32 cyc = timer_32k_base ? __raw_readl(timer_32k_base) : 0;
return cyc_to_fixed_sched_clock(&cd, cyc, (u32)~0, SC_MULT, SC_SHIFT);
}
@@ -140,7 +70,7 @@ unsigned long long notrace omap_32k_sched_clock(void)
static void notrace omap_update_sched_clock(void)
{
- u32 cyc = clocksource_32k.read(&clocksource_32k);
+ u32 cyc = timer_32k_base ? __raw_readl(timer_32k_base) : 0;
update_sched_clock(&cd, cyc, (u32)~0);
}
@@ -153,6 +83,7 @@ static void notrace omap_update_sched_clock(void)
*/
static struct timespec persistent_ts;
static cycles_t cycles, last_cycles;
+static unsigned int persistent_mult, persistent_shift;
void read_persistent_clock(struct timespec *ts)
{
unsigned long long nsecs;
@@ -160,11 +91,10 @@ void read_persistent_clock(struct timespec *ts)
struct timespec *tsp = &persistent_ts;
last_cycles = cycles;
- cycles = clocksource_32k.read(&clocksource_32k);
+ cycles = timer_32k_base ? __raw_readl(timer_32k_base) : 0;
delta = cycles - last_cycles;
- nsecs = clocksource_cyc2ns(delta,
- clocksource_32k.mult, clocksource_32k.shift);
+ nsecs = clocksource_cyc2ns(delta, persistent_mult, persistent_shift);
timespec_add_ns(tsp, nsecs);
*ts = *tsp;
@@ -176,29 +106,46 @@ int __init omap_init_clocksource_32k(void)
"%s: can't register clocksource!\n";
if (cpu_is_omap16xx() || cpu_class_is_omap2()) {
+ u32 pbase;
+ unsigned long size = SZ_4K;
+ void __iomem *base;
struct clk *sync_32k_ick;
- if (cpu_is_omap16xx())
- clocksource_32k.read = omap16xx_32k_read;
- else if (cpu_is_omap2420())
- clocksource_32k.read = omap2420_32k_read;
+ if (cpu_is_omap16xx()) {
+ pbase = OMAP16XX_TIMER_32K_SYNCHRONIZED;
+ size = SZ_1K;
+ } else if (cpu_is_omap2420())
+ pbase = OMAP2420_32KSYNCT_BASE + 0x10;
else if (cpu_is_omap2430())
- clocksource_32k.read = omap2430_32k_read;
+ pbase = OMAP2430_32KSYNCT_BASE + 0x10;
else if (cpu_is_omap34xx())
- clocksource_32k.read = omap34xx_32k_read;
+ pbase = OMAP3430_32KSYNCT_BASE + 0x10;
else if (cpu_is_omap44xx())
- clocksource_32k.read = omap44xx_32k_read;
+ pbase = OMAP4430_32KSYNCT_BASE + 0x10;
else
return -ENODEV;
+ /* For this to work we must have a static mapping in io.c for this area */
+ base = ioremap(pbase, size);
+ if (!base)
+ return -ENODEV;
+
sync_32k_ick = clk_get(NULL, "omap_32ksync_ick");
if (!IS_ERR(sync_32k_ick))
clk_enable(sync_32k_ick);
- offset_32k = clocksource_32k.read(&clocksource_32k);
+ timer_32k_base = base;
+
+ /*
+ * 120000 rough estimate from the calculations in
+ * __clocksource_updatefreq_scale.
+ */
+ clocks_calc_mult_shift(&persistent_mult, &persistent_shift,
+ 32768, NSEC_PER_SEC, 120000);
- if (clocksource_register_hz(&clocksource_32k, 32768))
- printk(err, clocksource_32k.name);
+ if (clocksource_mmio_init(base, "32k_counter", 32768, 250, 32,
+ clocksource_mmio_readl_up))
+ printk(err, "32k_counter");
init_fixed_sched_clock(&cd, omap_update_sched_clock, 32,
32768, SC_MULT, SC_SHIFT);
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