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authorRussell King <rmk+kernel@armlinux.org.uk>2018-11-14 19:13:02 +0000
committerRussell King <rmk+kernel@armlinux.org.uk>2019-05-09 16:26:29 +0100
commita44c1d700c848e221d80aab1029d36a60d21a0f4 (patch)
treeecf033d8da47d219f6e0730dd7b8105c7af7caea /arch/arm/mach-rpc
parente93c9c99a629c61837d5a7fc2120cd2b6c70dbdd (diff)
downloadlinux-a44c1d700c848e221d80aab1029d36a60d21a0f4.tar.bz2
ARM: riscpc: replace gettimeoffset() with clocksource
Replace the old gettimeoffset() interface (which became buggy in several ways) with a clocksource that atomically reads the count and status from the timer, and corrects the count as appropriate ensuring proper resolution of time without time warping backwards. We keep the original periodic timer non-clock event implementation to provide the kernel with a regular source of interrupts, which are required to keep the clocksource properly updated. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/mach-rpc')
-rw-r--r--arch/arm/mach-rpc/time.c38
1 files changed, 25 insertions, 13 deletions
diff --git a/arch/arm/mach-rpc/time.c b/arch/arm/mach-rpc/time.c
index 2689771c1d38..1c84efc9db1f 100644
--- a/arch/arm/mach-rpc/time.c
+++ b/arch/arm/mach-rpc/time.c
@@ -13,7 +13,7 @@
* 04-Dec-1997 RMK Updated for new arch/arm/time.c
* 13=Jun-2004 DS Moved to arch/arm/common b/c shared w/CLPS7500
*/
-#include <linux/timex.h>
+#include <linux/clocksource.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
@@ -27,11 +27,15 @@
#define RPC_CLOCK_FREQ 2000000
#define RPC_LATCH DIV_ROUND_CLOSEST(RPC_CLOCK_FREQ, HZ)
-static u32 ioc_timer_gettimeoffset(void)
+static u32 ioc_time;
+
+static u64 ioc_timer_read(struct clocksource *cs)
{
unsigned int count1, count2, status;
- long offset;
+ unsigned long flags;
+ u32 ticks;
+ local_irq_save(flags);
ioc_writeb (0, IOC_T0LATCH);
barrier ();
count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
@@ -41,27 +45,34 @@ static u32 ioc_timer_gettimeoffset(void)
ioc_writeb (0, IOC_T0LATCH);
barrier ();
count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
+ ticks = ioc_time + RPC_LATCH - count2;
+ local_irq_restore(flags);
- offset = count2;
if (count2 < count1) {
/*
- * We have not had an interrupt between reading count1
- * and count2.
+ * The timer has not reloaded between reading count1 and
+ * count2, check whether an interrupt was actually pending.
*/
if (status & (1 << 5))
- offset -= RPC_LATCH;
+ ticks += RPC_LATCH;
} else if (count2 > count1) {
/*
- * We have just had another interrupt between reading
- * count1 and count2.
+ * The timer has reloaded, so count2 indicates the new
+ * count since the wrap. The interrupt would not have
+ * been processed, so add the missed ticks.
*/
- offset -= RPC_LATCH;
+ ticks += RPC_LATCH;
}
- offset = (RPC_LATCH - offset) * (tick_nsec / 1000);
- return DIV_ROUND_CLOSEST(offset, RPC_LATCH) * 1000;
+ return ticks;
}
+static struct clocksource ioctime_clocksource = {
+ .read = ioc_timer_read,
+ .mask = CLOCKSOURCE_MASK(32),
+ .rating = 100,
+};
+
void __init ioctime_init(void)
{
ioc_writeb(RPC_LATCH & 255, IOC_T0LTCHL);
@@ -72,6 +83,7 @@ void __init ioctime_init(void)
static irqreturn_t
ioc_timer_interrupt(int irq, void *dev_id)
{
+ ioc_time += RPC_LATCH;
timer_tick();
return IRQ_HANDLED;
}
@@ -86,7 +98,7 @@ static struct irqaction ioc_timer_irq = {
*/
void __init ioc_timer_init(void)
{
- arch_gettimeoffset = ioc_timer_gettimeoffset;
+ WARN_ON(clocksource_register_hz(&ioctime_clocksource, RPC_CLOCK_FREQ));
ioctime_init();
setup_irq(IRQ_TIMER0, &ioc_timer_irq);
}