[PATCH 4/4] clocksource/vt8500: Add register R/W functions
From: Roman Volkov
Date: Sun Dec 20 2015 - 17:30:06 EST
From: Roman Volkov <rvolkov@xxxxxxxxx>
vt8500 timer requires special synchronization for accessing some of its
registers. Define special read and write functions to handle this process
transparently.
To perform a read from the Timer Count register, user must write a one
to the Timer Control register and wait for completion flag by polling the
Timer Read Count Active bit.
To perform a write to the Count or Match registers, user must poll the
write completion flag for the corresponding register to ensure that the
previous write completed and then write the actual value.
Signed-off-by: Roman Volkov <rvolkov@xxxxxxxxx>
---
drivers/clocksource/vt8500_timer.c | 90 +++++++++++++++++++++++++++-----------
1 file changed, 65 insertions(+), 25 deletions(-)
diff --git a/drivers/clocksource/vt8500_timer.c b/drivers/clocksource/vt8500_timer.c
index 7649852..4d7513f 100644
--- a/drivers/clocksource/vt8500_timer.c
+++ b/drivers/clocksource/vt8500_timer.c
@@ -38,36 +38,75 @@
#define VT8500_TIMER_OFFSET 0x0100
#define VT8500_TIMER_HZ 3000000
-#define TIMER_MATCH_VAL 0x0000
+#define TIMER_MATCH0_VAL 0
+#define TIMER_MATCH1_VAL 0x04
+#define TIMER_MATCH2_VAL 0x08
+#define TIMER_MATCH3_VAL 0x0c
#define TIMER_COUNT_VAL 0x0010
#define TIMER_STATUS_VAL 0x0014
#define TIMER_IER_VAL 0x001c /* interrupt enable */
#define TIMER_CTRL_VAL 0x0020
#define TIMER_AS_VAL 0x0024 /* access status */
-#define TIMER_COUNT_R_ACTIVE (1 << 5) /* not ready for read */
-#define TIMER_COUNT_W_ACTIVE (1 << 4) /* not ready for write */
-#define TIMER_MATCH_W_ACTIVE (1 << 0) /* not ready for write */
-
-#define timer_readl(addr) readl_relaxed(regbase + addr)
-#define timer_writel(v, addr) writel_relaxed(v, regbase + addr)
+/* R/W status flags */
+#define TIMER_COUNT_R_ACTIVE (1 << 5)
+#define TIMER_COUNT_W_ACTIVE (1 << 4)
+#define TIMER_MATCH3_W_ACTIVE (1 << 3)
+#define TIMER_MATCH2_W_ACTIVE (1 << 2)
+#define TIMER_MATCH1_W_ACTIVE (1 << 1)
+#define TIMER_MATCH0_W_ACTIVE (1 << 0)
+
+#define vt8500_timer_sync(bit) { while (readl_relaxed \
+ (regbase + TIMER_AS_VAL) & bit) \
+ cpu_relax(); }
#define MIN_OSCR_DELTA 16
static void __iomem *regbase;
-static cycle_t vt8500_timer_read(struct clocksource *cs)
+static void vt8500_timer_write(unsigned long reg, u32 value)
+{
+ switch (reg) {
+ case TIMER_COUNT_VAL:
+ vt8500_timer_sync(TIMER_COUNT_W_ACTIVE);
+ break;
+ case TIMER_MATCH0_VAL:
+ vt8500_timer_sync(TIMER_MATCH0_W_ACTIVE);
+ break;
+ case TIMER_MATCH1_VAL:
+ vt8500_timer_sync(TIMER_MATCH1_W_ACTIVE);
+ break;
+ case TIMER_MATCH2_VAL:
+ vt8500_timer_sync(TIMER_MATCH2_W_ACTIVE);
+ break;
+ case TIMER_MATCH3_VAL:
+ vt8500_timer_sync(TIMER_MATCH3_W_ACTIVE);
+ break;
+ }
+
+ writel_relaxed(value, regbase + reg);
+}
+
+static u32 vt8500_timer_read(unsigned long reg)
{
- timer_writel(3, TIMER_CTRL_VAL);
- while (timer_readl(TIMER_AS_VAL) & TIMER_COUNT_R_ACTIVE)
- cpu_relax();
+ if (reg == TIMER_COUNT_VAL) {
+ vt8500_timer_write(TIMER_CTRL_VAL, 3);
+ vt8500_timer_sync(TIMER_COUNT_R_ACTIVE);
- return timer_readl(TIMER_COUNT_VAL);
+ return readl_relaxed(regbase + TIMER_COUNT_VAL);
+ }
+
+ return readl_relaxed(regbase + reg);
+}
+
+static cycle_t vt8500_oscr0_read(struct clocksource *cs)
+{
+ return vt8500_timer_read(TIMER_COUNT_VAL);
}
static struct clocksource clocksource = {
.name = "vt8500_timer",
.rating = 200,
- .read = vt8500_timer_read,
+ .read = vt8500_oscr0_read,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
@@ -75,23 +114,24 @@ static struct clocksource clocksource = {
static int vt8500_timer_set_next_event(unsigned long cycles,
struct clock_event_device *evt)
{
- cycle_t alarm = clocksource.read(&clocksource) + cycles;
- while (timer_readl(TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
- cpu_relax();
- timer_writel((unsigned long)alarm, TIMER_MATCH_VAL);
+ unsigned long alarm = vt8500_timer_read(TIMER_COUNT_VAL) + cycles;
- if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
+ vt8500_timer_write(TIMER_MATCH0_VAL, alarm);
+ if ((signed)(alarm - vt8500_timer_read(
+ TIMER_COUNT_VAL)) <= MIN_OSCR_DELTA) {
return -ETIME;
+ }
- timer_writel(1, TIMER_IER_VAL);
+ vt8500_timer_write(TIMER_IER_VAL, 1);
return 0;
}
static int vt8500_shutdown(struct clock_event_device *evt)
{
- timer_writel(timer_readl(TIMER_CTRL_VAL) | 1, TIMER_CTRL_VAL);
- timer_writel(0, TIMER_IER_VAL);
+ vt8500_timer_write(TIMER_CTRL_VAL,
+ vt8500_timer_read(TIMER_CTRL_VAL) | 1);
+ vt8500_timer_write(TIMER_IER_VAL, 0);
return 0;
}
@@ -107,7 +147,7 @@ static struct clock_event_device clockevent = {
static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
{
struct clock_event_device *evt = dev_id;
- timer_writel(0xf, TIMER_STATUS_VAL);
+ vt8500_timer_write(TIMER_STATUS_VAL, 0xf);
evt->event_handler(evt);
return IRQ_HANDLED;
@@ -137,9 +177,9 @@ static void __init vt8500_timer_init(struct device_node *np)
return;
}
- timer_writel(1, TIMER_CTRL_VAL);
- timer_writel(0xf, TIMER_STATUS_VAL);
- timer_writel(~0, TIMER_MATCH_VAL);
+ vt8500_timer_write(TIMER_CTRL_VAL, 1);
+ vt8500_timer_write(TIMER_STATUS_VAL, 0xf);
+ vt8500_timer_write(TIMER_MATCH0_VAL, ~0);
if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
--
2.6.2
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