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Subject[PATCH v6 3/7] clocksource/drivers: timer-atmel-tcb: add clockevent device on separate channel
Date
Add an other clockevent device that uses a separate TCB channel when
available.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
drivers/clocksource/timer-atmel-tcb.c | 217 +++++++++++++++++++++++++-
1 file changed, 212 insertions(+), 5 deletions(-)

diff --git a/drivers/clocksource/timer-atmel-tcb.c b/drivers/clocksource/timer-atmel-tcb.c
index 3064881af963..2dd032d30fac 100644
--- a/drivers/clocksource/timer-atmel-tcb.c
+++ b/drivers/clocksource/timer-atmel-tcb.c
@@ -32,7 +32,7 @@ struct atmel_tcb_clksrc {
bool clk_enabled;
};

-static struct atmel_tcb_clksrc tc;
+static struct atmel_tcb_clksrc tc, tce;

static struct clk *tcb_clk_get(struct device_node *node, int channel)
{
@@ -47,6 +47,203 @@ static struct clk *tcb_clk_get(struct device_node *node, int channel)
return of_clk_get_by_name(node->parent, "t0_clk");
}

+/*
+ * Clockevent device using its own channel
+ */
+
+static void tc_clkevt2_clk_disable(struct clock_event_device *d)
+{
+ clk_disable(tce.clk[0]);
+ tce.clk_enabled = false;
+}
+
+static void tc_clkevt2_clk_enable(struct clock_event_device *d)
+{
+ if (tce.clk_enabled)
+ return;
+ clk_enable(tce.clk[0]);
+ tce.clk_enabled = true;
+}
+
+static int tc_clkevt2_stop(struct clock_event_device *d)
+{
+ writel(0xff, tce.base + ATMEL_TC_IDR(tce.channels[0]));
+ writel(ATMEL_TC_CCR_CLKDIS, tce.base + ATMEL_TC_CCR(tce.channels[0]));
+
+ return 0;
+}
+
+static int tc_clkevt2_shutdown(struct clock_event_device *d)
+{
+ tc_clkevt2_stop(d);
+ if (!clockevent_state_detached(d))
+ tc_clkevt2_clk_disable(d);
+
+ return 0;
+}
+
+/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
+ * because using one of the divided clocks would usually mean the
+ * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
+ *
+ * A divided clock could be good for high resolution timers, since
+ * 30.5 usec resolution can seem "low".
+ */
+static int tc_clkevt2_set_oneshot(struct clock_event_device *d)
+{
+ if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
+ tc_clkevt2_stop(d);
+
+ tc_clkevt2_clk_enable(d);
+
+ /* slow clock, count up to RC, then irq and stop */
+ writel(ATMEL_TC_CMR_TCLK(4) | ATMEL_TC_CMR_CPCSTOP |
+ ATMEL_TC_CMR_WAVE | ATMEL_TC_CMR_WAVESEL_UPRC,
+ tce.base + ATMEL_TC_CMR(tce.channels[0]));
+ writel(ATMEL_TC_CPCS, tce.base + ATMEL_TC_IER(tce.channels[0]));
+
+ return 0;
+}
+
+static int tc_clkevt2_set_periodic(struct clock_event_device *d)
+{
+ if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
+ tc_clkevt2_stop(d);
+
+ /* By not making the gentime core emulate periodic mode on top
+ * of oneshot, we get lower overhead and improved accuracy.
+ */
+ tc_clkevt2_clk_enable(d);
+
+ /* slow clock, count up to RC, then irq and restart */
+ writel(ATMEL_TC_CMR_TCLK(4) | ATMEL_TC_CMR_WAVE |
+ ATMEL_TC_CMR_WAVESEL_UPRC,
+ tce.base + ATMEL_TC_CMR(tce.channels[0]));
+ writel((32768 + HZ / 2) / HZ, tce.base + ATMEL_TC_RC(tce.channels[0]));
+
+ /* Enable clock and interrupts on RC compare */
+ writel(ATMEL_TC_CPCS, tce.base + ATMEL_TC_IER(tce.channels[0]));
+ writel(ATMEL_TC_CCR_CLKEN | ATMEL_TC_CCR_SWTRG,
+ tce.base + ATMEL_TC_CCR(tce.channels[0]));
+
+ return 0;
+}
+
+static int tc_clkevt2_next_event(unsigned long delta,
+ struct clock_event_device *d)
+{
+ writel(delta, tce.base + ATMEL_TC_RC(tce.channels[0]));
+ writel(ATMEL_TC_CCR_CLKEN | ATMEL_TC_CCR_SWTRG,
+ tce.base + ATMEL_TC_CCR(tce.channels[0]));
+
+ return 0;
+}
+
+static irqreturn_t tc_clkevt2_irq(int irq, void *handle)
+{
+ unsigned int sr;
+
+ sr = readl(tce.base + ATMEL_TC_SR(tce.channels[0]));
+ if (sr & ATMEL_TC_CPCS) {
+ tce.clkevt.event_handler(&tce.clkevt);
+ return IRQ_HANDLED;
+ }
+
+ return IRQ_NONE;
+}
+
+static void tc_clkevt2_suspend(struct clock_event_device *d)
+{
+ tce.cache[0].cmr = readl(tce.base + ATMEL_TC_CMR(tce.channels[0]));
+ tce.cache[0].imr = readl(tce.base + ATMEL_TC_IMR(tce.channels[0]));
+ tce.cache[0].rc = readl(tce.base + ATMEL_TC_RC(tce.channels[0]));
+ tce.cache[0].clken = !!(readl(tce.base + ATMEL_TC_SR(tce.channels[0])) &
+ ATMEL_TC_CLKSTA);
+}
+
+static void tc_clkevt2_resume(struct clock_event_device *d)
+{
+ /* Restore registers for the channel, RA and RB are not used */
+ writel(tce.cache[0].cmr, tc.base + ATMEL_TC_CMR(tce.channels[0]));
+ writel(tce.cache[0].rc, tc.base + ATMEL_TC_RC(tce.channels[0]));
+ writel(0, tc.base + ATMEL_TC_RA(tce.channels[0]));
+ writel(0, tc.base + ATMEL_TC_RB(tce.channels[0]));
+ /* Disable all the interrupts */
+ writel(0xff, tc.base + ATMEL_TC_IDR(tce.channels[0]));
+ /* Reenable interrupts that were enabled before suspending */
+ writel(tce.cache[0].imr, tc.base + ATMEL_TC_IER(tce.channels[0]));
+
+ /* Start the clock if it was used */
+ if (tce.cache[0].clken)
+ writel(ATMEL_TC_CCR_CLKEN | ATMEL_TC_CCR_SWTRG,
+ tc.base + ATMEL_TC_CCR(tce.channels[0]));
+}
+
+static int __init tc_clkevt_register(struct device_node *node,
+ struct regmap *regmap, void __iomem *base,
+ int channel, int irq, int bits)
+{
+ int ret;
+ struct clk *slow_clk;
+
+ tce.regmap = regmap;
+ tce.base = base;
+ tce.channels[0] = channel;
+ tce.irq = irq;
+
+ slow_clk = of_clk_get_by_name(node->parent, "slow_clk");
+ if (IS_ERR(slow_clk))
+ return PTR_ERR(slow_clk);
+
+ ret = clk_prepare_enable(slow_clk);
+ if (ret)
+ return ret;
+
+ tce.clk[0] = tcb_clk_get(node, tce.channels[0]);
+ if (IS_ERR(tce.clk[0])) {
+ ret = PTR_ERR(tce.clk[0]);
+ goto err_slow;
+ }
+
+ snprintf(tce.name, sizeof(tce.name), "%s:%d",
+ kbasename(node->parent->full_name), channel);
+ tce.clkevt.cpumask = cpumask_of(0);
+ tce.clkevt.name = tce.name;
+ tce.clkevt.set_next_event = tc_clkevt2_next_event,
+ tce.clkevt.set_state_shutdown = tc_clkevt2_shutdown,
+ tce.clkevt.set_state_periodic = tc_clkevt2_set_periodic,
+ tce.clkevt.set_state_oneshot = tc_clkevt2_set_oneshot,
+ tce.clkevt.suspend = tc_clkevt2_suspend,
+ tce.clkevt.resume = tc_clkevt2_resume,
+ tce.clkevt.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
+ tce.clkevt.rating = 140;
+
+ /* try to enable clk to avoid future errors in mode change */
+ ret = clk_prepare_enable(tce.clk[0]);
+ if (ret)
+ goto err_slow;
+ clk_disable(tce.clk[0]);
+
+ clockevents_config_and_register(&tce.clkevt, 32768, 1,
+ CLOCKSOURCE_MASK(bits));
+
+ ret = request_irq(tce.irq, tc_clkevt2_irq, IRQF_TIMER | IRQF_SHARED,
+ tce.clkevt.name, &tce);
+ if (ret)
+ goto err_clk;
+
+ tce.registered = true;
+
+ return 0;
+
+err_clk:
+ clk_unprepare(tce.clk[0]);
+err_slow:
+ clk_disable_unprepare(slow_clk);
+
+ return ret;
+}
+
/*
* Clocksource and clockevent using the same channel(s)
*/
@@ -362,7 +559,7 @@ static int __init tcb_clksrc_init(struct device_node *node)
u32 channel;
int bits, irq, err, chan1 = -1;

- if (tc.registered)
+ if (tc.registered && tce.registered)
return -ENODEV;

/*
@@ -394,12 +591,22 @@ static int __init tcb_clksrc_init(struct device_node *node)
return irq;
}

+ if (tc.registered)
+ return tc_clkevt_register(node, regmap, tcb_base, channel, irq,
+ bits);
+
if (bits == 16) {
of_property_read_u32_index(node, "reg", 1, &chan1);
if (chan1 == -1) {
- pr_err("%s: clocksource needs two channels\n",
- node->parent->full_name);
- return -EINVAL;
+ if (tce.registered) {
+ pr_err("%s: clocksource needs two channels\n",
+ node->parent->full_name);
+ return -EINVAL;
+ } else {
+ return tc_clkevt_register(node, regmap,
+ tcb_base, channel,
+ irq, bits);
+ }
}
}

--
2.19.0.rc2
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