linux-kernel - [RFC v3 2/2] clocksource: timer-davinci: add support for clocksource

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Message-Id: <20190605083334.22383-3-brgl@bgdev.pl>
Date:   Wed,  5 Jun 2019 10:33:34 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Sekhar Nori <nsekhar@...com>, Kevin Hilman <khilman@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Lechner <david@...hnology.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: [RFC v3 2/2] clocksource: timer-davinci: add support for clocksource

From: Bartosz Golaszewski <bgolaszewski@...libre.com>

Extend the davinci-timer driver to also register a clock source.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
---
 drivers/clocksource/timer-davinci.c | 85 +++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/drivers/clocksource/timer-davinci.c b/drivers/clocksource/timer-davinci.c
index f8959dccae54..a9ca02390b66 100644
--- a/drivers/clocksource/timer-davinci.c
+++ b/drivers/clocksource/timer-davinci.c
@@ -43,6 +43,8 @@
 #define DAVINCI_TIMER_MIN_DELTA			0x01
 #define DAVINCI_TIMER_MAX_DELTA			0xfffffffe
 
+#define DAVINCI_TIMER_CLKSRC_BITS		32
+
 #define DAVINCI_TIMER_TGCR_DEFAULT \
 		(DAVINCI_TIMER_TIMMODE_32BIT_UNCHAINED | DAVINCI_TIMER_UNRESET)
 
@@ -52,6 +54,16 @@ struct davinci_clockevent {
 	unsigned int cmp_off;
 };
 
+/*
+ * This must be globally accessible by davinci_timer_read_sched_clock(), so
+ * let's keep it here.
+ */
+static struct {
+	struct clocksource dev;
+	void __iomem *base;
+	unsigned int tim_off;
+} davinci_clocksource;
+
 static struct davinci_clockevent *
 to_davinci_clockevent(struct clock_event_device *clockevent)
 {
@@ -166,6 +178,53 @@ static irqreturn_t davinci_timer_irq_timer(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+static u64 notrace davinci_timer_read_sched_clock(void)
+{
+	return readl_relaxed(davinci_clocksource.base +
+			     davinci_clocksource.tim_off);
+}
+
+static u64 davinci_clocksource_read(struct clocksource *dev)
+{
+	return davinci_timer_read_sched_clock();
+}
+
+/*
+ * Standard use-case: we're using tim12 for clockevent and tim34 for
+ * clocksource. The default is making the former run in oneshot mode
+ * and the latter in periodic mode.
+ */
+static void davinci_clocksource_init_tim34(void __iomem *base)
+{
+	int tcr;
+
+	tcr = DAVINCI_TIMER_ENAMODE_PERIODIC <<
+		DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
+	tcr |= DAVINCI_TIMER_ENAMODE_ONESHOT <<
+		DAVINCI_TIMER_ENAMODE_SHIFT_TIM12;
+
+	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM34);
+	writel_relaxed(UINT_MAX, base + DAVINCI_TIMER_REG_PRD34);
+	writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
+}
+
+/*
+ * Special use-case on da830: the DSP may use tim34. We're using tim12 for
+ * both clocksource and clockevent. We set tim12 to periodic and don't touch
+ * tim34.
+ */
+static void davinci_clocksource_init_tim12(void __iomem *base)
+{
+	unsigned int tcr;
+
+	tcr = DAVINCI_TIMER_ENAMODE_PERIODIC <<
+		DAVINCI_TIMER_ENAMODE_SHIFT_TIM12;
+
+	writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM12);
+	writel_relaxed(UINT_MAX, base + DAVINCI_TIMER_REG_PRD12);
+	writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR);
+}
+
 static void davinci_timer_init(void __iomem *base)
 {
 	/* Set clock to internal mode and disable it. */
@@ -248,6 +307,32 @@ int __init davinci_timer_register(struct clk *clk,
 					DAVINCI_TIMER_MIN_DELTA,
 					DAVINCI_TIMER_MAX_DELTA);
 
+	davinci_clocksource.dev.rating = 300;
+	davinci_clocksource.dev.read = davinci_clocksource_read;
+	davinci_clocksource.dev.mask =
+			CLOCKSOURCE_MASK(DAVINCI_TIMER_CLKSRC_BITS);
+	davinci_clocksource.dev.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+	davinci_clocksource.base = base;
+
+	if (timer_cfg->cmp_off) {
+		davinci_clocksource.dev.name = "tim12";
+		davinci_clocksource.tim_off = DAVINCI_TIMER_REG_TIM12;
+		davinci_clocksource_init_tim12(base);
+	} else {
+		davinci_clocksource.dev.name = "tim34";
+		davinci_clocksource.tim_off = DAVINCI_TIMER_REG_TIM34;
+		davinci_clocksource_init_tim34(base);
+	}
+
+	rv = clocksource_register_hz(&davinci_clocksource.dev, tick_rate);
+	if (rv) {
+		pr_err("Unable to register clocksource");
+		return rv;
+	}
+
+	sched_clock_register(davinci_timer_read_sched_clock,
+			     DAVINCI_TIMER_CLKSRC_BITS, tick_rate);
+
 	return 0;
 }
 
-- 
2.21.0