arch_timer: Move to generic sched_clock framework

Register with the generic sched_clock framework now that it
supports 64 bits. This fixes two problems with the current
sched_clock support for machines using the architected timers.
First off, we don't subtract the start value from subsequent
sched_clock calls so we can potentially start off with
sched_clock returning gigantic numbers. Second, there is no
support for suspend/resume handling so problems such as discussed
in 6a4dae5 (ARM: 7565/1: sched: stop sched_clock() during
suspend, 2012-10-23) can happen without this patch. Finally, it
allows us to move the sched_clock setup into drivers clocksource
out of the arch ports.

Cc: Christopher Covington <cov@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>

4 files changed, 11 insertions, 24 deletions

diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
index 221f07b11ccb..1791f12c180b 100644
--- a/arch/arm/kernel/arch_timer.c
+++ b/arch/arm/kernel/arch_timer.c
@@ -11,7 +11,6 @@
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/errno.h>
-#include <linux/sched_clock.h>
 
 #include <asm/delay.h>
 
@@ -22,13 +21,6 @@ static unsigned long arch_timer_read_counter_long(void)
         return arch_timer_read_counter();
 }
 
-static u32 sched_clock_mult __read_mostly;
-
-static unsigned long long notrace arch_timer_sched_clock(void)
-{
-        return arch_timer_read_counter() * sched_clock_mult;
-}
-
 static struct delay_timer arch_delay_timer;
 
 static void __init arch_timer_delay_timer_register(void)
@@ -48,11 +40,5 @@ int __init arch_timer_arch_init(void)
 
         arch_timer_delay_timer_register();
 
-        /* Cache the sched_clock multiplier to save a divide in the hot path. */
-        sched_clock_mult = NSEC_PER_SEC / arch_timer_rate;
-        sched_clock_func = arch_timer_sched_clock;
-        pr_info("sched_clock: ARM arch timer >56 bits at %ukHz, resolution %uns\n",
-                arch_timer_rate / 1000, sched_clock_mult);
-
         return 0;
 }
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c04454876bcb..35fd0eb57270 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -14,6 +14,7 @@ config ARM64
         select GENERIC_IOMAP
         select GENERIC_IRQ_PROBE
         select GENERIC_IRQ_SHOW
+        select GENERIC_SCHED_CLOCK
         select GENERIC_SMP_IDLE_THREAD
         select GENERIC_TIME_VSYSCALL
         select HARDIRQS_SW_RESEND
diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
index 03dc3718eb13..29c39d5d77e3 100644
--- a/arch/arm64/kernel/time.c
+++ b/arch/arm64/kernel/time.c
@@ -61,13 +61,6 @@ unsigned long profile_pc(struct pt_regs *regs)
 EXPORT_SYMBOL(profile_pc);
 #endif
 
-static u64 sched_clock_mult __read_mostly;
-
-unsigned long long notrace sched_clock(void)
-{
-        return arch_timer_read_counter() * sched_clock_mult;
-}
-
 void __init time_init(void)
 {
         u32 arch_timer_rate;
@@ -78,9 +71,6 @@ void __init time_init(void)
         if (!arch_timer_rate)
                 panic("Unable to initialise architected timer.\n");
 
-        /* Cache the sched_clock multiplier to save a divide in the hot path. */
-        sched_clock_mult = NSEC_PER_SEC / arch_timer_rate;
-
         /* Calibrate the delay loop directly */
         lpj_fine = arch_timer_rate / HZ;
 }
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index fbd9ccd5e114..5d527895c74d 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -19,6 +19,7 @@
 #include <linux/of_address.h>
 #include <linux/io.h>
 #include <linux/slab.h>
+#include <linux/sched_clock.h>
 
 #include <asm/arch_timer.h>
 #include <asm/virt.h>
@@ -471,6 +472,15 @@ static int __init arch_timer_register(void)
                 goto out;
         }
 
+        clocksource_register_hz(&clocksource_counter, arch_timer_rate);
+        cyclecounter.mult = clocksource_counter.mult;
+        cyclecounter.shift = clocksource_counter.shift;
+        timecounter_init(&timecounter, &cyclecounter,
+                         arch_counter_get_cntvct());
+
+        /* 56 bits minimum, so we assume worst case rollover */
+        sched_clock_register(arch_timer_read_counter, 56, arch_timer_rate);
+
         if (arch_timer_use_virtual) {
                 ppi = arch_timer_ppi[VIRT_PPI];
                 err = request_percpu_irq(ppi, arch_timer_handler_virt,