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

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Message-Id: <20190417144709.19588-3-brgl@bgdev.pl>
Date:   Wed, 17 Apr 2019 16:47:09 +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 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 | 70 +++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/drivers/clocksource/timer-davinci.c b/drivers/clocksource/timer-davinci.c
index d30f81a4088e..d630fca98123 100644
--- a/drivers/clocksource/timer-davinci.c
+++ b/drivers/clocksource/timer-davinci.c
@@ -42,6 +42,8 @@
 #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)
 
@@ -59,6 +61,16 @@ struct davinci_clockevent {
 	unsigned int enamode_mask;
 };
 
+/*
+ * 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)
 {
@@ -148,6 +160,32 @@ 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();
+}
+
+static void davinci_clocksource_init(void __iomem *base, unsigned int tim_off,
+				     unsigned int prd_off, unsigned int shift)
+{
+	davinci_reg_update(base, DAVINCI_TIMER_REG_TCR,
+			   DAVINCI_TIMER_ENAMODE_MASK << shift,
+			   DAVINCI_TIMER_ENAMODE_DISABLED << shift);
+
+	writel_relaxed(0x0, base + tim_off);
+	writel_relaxed(UINT_MAX, base + prd_off);
+
+	davinci_reg_update(base, DAVINCI_TIMER_REG_TCR,
+			   DAVINCI_TIMER_ENAMODE_MASK << shift,
+			   DAVINCI_TIMER_ENAMODE_PERIODIC << shift);
+}
+
 static void davinci_timer_init(void __iomem *base)
 {
 	/* Set clock to internal mode and disable it. */
@@ -235,6 +273,38 @@ 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(base,
+					 DAVINCI_TIMER_REG_TIM12,
+					 DAVINCI_TIMER_REG_PRD12,
+					 DAVINCI_TIMER_ENAMODE_SHIFT_TIM12);
+	} else {
+		davinci_clocksource.dev.name = "tim34";
+		davinci_clocksource.tim_off = DAVINCI_TIMER_REG_TIM34;
+		davinci_clocksource_init(base,
+					 DAVINCI_TIMER_REG_TIM34,
+					 DAVINCI_TIMER_REG_PRD34,
+					 DAVINCI_TIMER_ENAMODE_SHIFT_TIM34);
+	}
+
+	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