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Subject[PATCH 6/7] clocksource/cadence_ttc: Use only one counter
Date
Currently the driver uses two of the three counters the TTC provides to
implement a clocksource and a clockevent device. By using the TTC's
match feature we can implement both use cases using a single counter
only.
The old approach is to use timer over-/underflow to generate an
interrupt. Using the match register allows to generate an interrupt on
arbitrary counter values. This way a dedicated clockevent counter can be
avoided.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
---
drivers/clocksource/cadence_ttc_timer.c | 92 +++++++++++----------------------
1 file changed, 31 insertions(+), 61 deletions(-)

diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c
index 421b942dd707..01dba97cee84 100644
--- a/drivers/clocksource/cadence_ttc_timer.c
+++ b/drivers/clocksource/cadence_ttc_timer.c
@@ -48,6 +48,7 @@
#define TTC_CNT_CNTRL_OFFSET 0x0C /* Counter Control Reg, RW */
#define TTC_COUNT_VAL_OFFSET 0x18 /* Counter Value Reg, RO */
#define TTC_INTR_VAL_OFFSET 0x24 /* Interval Count Reg, RW */
+#define TTC_MATCH1_OFFSET 0x30 /* Match reg, RW */
#define TTC_ISR_OFFSET 0x54 /* Interrupt Status Reg, RO */
#define TTC_IER_OFFSET 0x60 /* Interrupt Enable Reg, RW */

@@ -65,7 +66,10 @@
#define PRESCALE 2048 /* The exponent must match this */
#define CLK_CNTRL_PRESCALE ((PRESCALE_EXPONENT - 1) << 1)
#define CLK_CNTRL_PRESCALE_EN 1
-#define CNT_CNTRL_RESET (1 << 4)
+#define CNT_CNTRL_RESET BIT(4)
+#define CNT_CNTRL_MATCH BIT(3)
+
+#define TTC_INTERRUPT_MATCH1 BIT(1)

#define MAX_F_ERR 50

@@ -103,6 +107,7 @@ struct ttc_timer_clocksource {
struct ttc_timer_clockevent {
struct ttc_timer ttc;
struct clock_event_device ce;
+ unsigned long interval;
};

#define to_ttc_timer_clkevent(x) \
@@ -116,25 +121,20 @@ static void __iomem *ttc_sched_clock_val_reg;
* @timer: Pointer to the timer instance
* @cycles: Timer interval ticks
**/
-static void ttc_set_interval(struct ttc_timer *timer,
- unsigned long cycles)
+static void ttc_set_interval(struct ttc_timer *timer, unsigned long cycles)
{
- u32 ctrl_reg;
+ struct ttc_timer_clockevent *ttcce = container_of(timer,
+ struct ttc_timer_clockevent, ttc);

- /* Disable the counter, set the counter value and re-enable counter */
- ctrl_reg = __raw_readl(timer->base_addr + TTC_CNT_CNTRL_OFFSET);
- ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
- __raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
+ /* set interval */
+ u32 reg = __raw_readl(timer->base_addr + TTC_COUNT_VAL_OFFSET);
+ reg += cycles;
+ __raw_writel(reg, timer->base_addr + TTC_MATCH1_OFFSET);

- __raw_writel(cycles, timer->base_addr + TTC_INTR_VAL_OFFSET);
+ /* enable match interrupt */
+ __raw_writel(TTC_INTERRUPT_MATCH1, timer->base_addr + TTC_IER_OFFSET);

- /*
- * Reset the counter (0x10) so that it starts from 0, one-shot
- * mode makes this needed for timing to be right.
- */
- ctrl_reg |= CNT_CNTRL_RESET;
- ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
- __raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
+ ttcce->interval = cycles;
}

/**
@@ -152,6 +152,8 @@ static irqreturn_t ttc_clock_event_interrupt(int irq, void *dev_id)

/* Acknowledge the interrupt and call event handler */
__raw_readl(timer->base_addr + TTC_ISR_OFFSET);
+ if (ttce->ce.mode == CLOCK_EVT_MODE_PERIODIC)
+ ttc_set_interval(timer, ttce->interval);

ttce->ce.event_handler(&ttce->ce);

@@ -205,7 +207,6 @@ static void ttc_set_mode(enum clock_event_mode mode,
{
struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
struct ttc_timer *timer = &ttce->ttc;
- u32 ctrl_reg;

switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
@@ -215,18 +216,9 @@ static void ttc_set_mode(enum clock_event_mode mode,
case CLOCK_EVT_MODE_ONESHOT:
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
- ctrl_reg = __raw_readl(timer->base_addr +
- TTC_CNT_CNTRL_OFFSET);
- ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
- __raw_writel(ctrl_reg,
- timer->base_addr + TTC_CNT_CNTRL_OFFSET);
+ __raw_writel(0, timer->base_addr + TTC_IER_OFFSET);
break;
case CLOCK_EVT_MODE_RESUME:
- ctrl_reg = __raw_readl(timer->base_addr +
- TTC_CNT_CNTRL_OFFSET);
- ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
- __raw_writel(ctrl_reg,
- timer->base_addr + TTC_CNT_CNTRL_OFFSET);
break;
}
}
@@ -392,17 +384,6 @@ static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
ttccs->cs.mask = CLOCKSOURCE_MASK(16);
ttccs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;

- /*
- * Setup the clock source counter to be an incrementing counter
- * with no interrupt and it rolls over at 0xFFFF. Pre-scale
- * it by 32 also. Let it start running now.
- */
- __raw_writel(0x0, ttccs->ttc.base_addr + TTC_IER_OFFSET);
- __raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
- ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
- __raw_writel(CNT_CNTRL_RESET,
- ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
-
err = clocksource_register_hz(&ttccs->cs, ttccs->ttc.freq / PRESCALE);
if (WARN_ON(err)) {
kfree(ttccs);
@@ -488,16 +469,6 @@ static void __init ttc_setup_clockevent(struct clk *clk,
ttcce->ce.irq = irq;
ttcce->ce.cpumask = cpu_possible_mask;

- /*
- * Setup the clock event timer to be an interval timer which
- * is prescaled by 32 using the interval interrupt. Leave it
- * disabled for now.
- */
- __raw_writel(0x23, ttcce->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
- __raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
- ttcce->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
- __raw_writel(0x1, ttcce->ttc.base_addr + TTC_IER_OFFSET);
-
err = request_irq(irq, ttc_clock_event_interrupt,
IRQF_DISABLED | IRQF_TIMER,
ttcce->ce.name, ttcce);
@@ -520,7 +491,7 @@ static void __init ttc_timer_init(struct device_node *timer)
{
unsigned int irq;
void __iomem *timer_baseaddr;
- struct clk *clk_cs, *clk_ce;
+ struct clk *clk;
static int initialized;
int clksel;

@@ -540,7 +511,7 @@ static void __init ttc_timer_init(struct device_node *timer)
BUG();
}

- irq = irq_of_parse_and_map(timer, 1);
+ irq = irq_of_parse_and_map(timer, 0);
if (irq <= 0) {
pr_err("ERROR: invalid interrupt number\n");
BUG();
@@ -548,22 +519,21 @@ static void __init ttc_timer_init(struct device_node *timer)

clksel = __raw_readl(timer_baseaddr + TTC_CLK_CNTRL_OFFSET);
clksel = !!(clksel & TTC_CLK_CNTRL_CSRC_MASK);
- clk_cs = of_clk_get(timer, clksel);
- if (IS_ERR(clk_cs)) {
+ clk = of_clk_get(timer, clksel);
+ if (IS_ERR(clk)) {
pr_err("ERROR: timer input clock not found\n");
BUG();
}

- clksel = __raw_readl(timer_baseaddr + 4 + TTC_CLK_CNTRL_OFFSET);
- clksel = !!(clksel & TTC_CLK_CNTRL_CSRC_MASK);
- clk_ce = of_clk_get(timer, clksel);
- if (IS_ERR(clk_ce)) {
- pr_err("ERROR: timer input clock not found\n");
- BUG();
- }
+ __raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
+ timer_baseaddr + TTC_CLK_CNTRL_OFFSET);
+
+ /* start timer in overflow and match mode */
+ __raw_writel(CNT_CNTRL_RESET | CNT_CNTRL_MATCH,
+ timer_baseaddr + TTC_CNT_CNTRL_OFFSET);

- ttc_setup_clocksource(clk_cs, timer_baseaddr);
- ttc_setup_clockevent(clk_ce, timer_baseaddr + 4, irq);
+ ttc_setup_clocksource(clk, timer_baseaddr);
+ ttc_setup_clockevent(clk, timer_baseaddr, irq);

pr_info("%s #0 at %p, irq=%d\n", timer->name, timer_baseaddr, irq);
}
--
1.8.4.2


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