linux-kernel - [PATCH V4 1/5] clocksource: timer-of: Support getting clock frequency from DT

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Date:   Mon,  1 Jul 2019 17:38:22 +0800
From:   Anson.Huang@....com
To:     daniel.lezcano@...aro.org, tglx@...utronix.de, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, leonard.crestez@....com,
        viresh.kumar@...aro.org, daniel.baluta@....com, ping.bai@....com,
        l.stach@...gutronix.de, abel.vesa@....com,
        andrew.smirnov@...il.com, ccaione@...libre.com, angus@...ea.ca,
        agx@...xcpu.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Linux-imx@....com
Subject: [PATCH V4 1/5] clocksource: timer-of: Support getting clock frequency from DT

From: Anson Huang <Anson.Huang@....com>

More and more platforms use platform driver model for clock driver,
so the clock driver is NOT ready during timer initialization phase,
it will cause timer initialization failed.

To support those platforms with upper scenario, introducing a new
flag TIMER_OF_CLOCK_FREQUENCY which is mutually exclusive with
TIMER_OF_CLOCK flag to support getting timer clock frequency from
DT's timer node, the property name should be "clock-frequency",
then of_clk operations can be skipped.

User needs to select either TIMER_OF_CLOCK_FREQUENCY or TIMER_OF_CLOCK
flag if want to use timer-of driver to initialize the clock rate.

Signed-off-by: Anson Huang <Anson.Huang@....com>
---
Changes since V3:
	- use hardcoded "clock-frequency" instead of adding new variable prop_name;
	- add pre-condition check for TIMER_OF_CLOCK and TIMER_OF_CLOCK_FREQUENCY, they MUST be exclusive.
---
 drivers/clocksource/timer-of.c | 29 +++++++++++++++++++++++++++++
 drivers/clocksource/timer-of.h |  7 ++++---
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/timer-of.c b/drivers/clocksource/timer-of.c
index 8054228..ab155cc 100644
--- a/drivers/clocksource/timer-of.c
+++ b/drivers/clocksource/timer-of.c
@@ -161,11 +161,30 @@ static __init int timer_of_base_init(struct device_node *np,
 	return 0;
 }
 
+static __init int timer_of_clk_frequency_init(struct device_node *np,
+					      struct of_timer_clk *of_clk)
+{
+	int ret;
+	u32 rate;
+
+	ret = of_property_read_u32(np, "clock-frequency", &rate);
+	if (!ret) {
+		of_clk->rate = rate;
+		of_clk->period = DIV_ROUND_UP(rate, HZ);
+	}
+
+	return ret;
+}
+
 int __init timer_of_init(struct device_node *np, struct timer_of *to)
 {
+	unsigned long clock_flags = TIMER_OF_CLOCK | TIMER_OF_CLOCK_FREQUENCY;
 	int ret = -EINVAL;
 	int flags = 0;
 
+	if (to->flags & clock_flags == clock_flags)
+		return ret;
+
 	if (to->flags & TIMER_OF_BASE) {
 		ret = timer_of_base_init(np, &to->of_base);
 		if (ret)
@@ -180,6 +199,13 @@ int __init timer_of_init(struct device_node *np, struct timer_of *to)
 		flags |= TIMER_OF_CLOCK;
 	}
 
+	if (to->flags & TIMER_OF_CLOCK_FREQUENCY) {
+		ret = timer_of_clk_frequency_init(np, &to->of_clk);
+		if (ret)
+			goto out_fail;
+		flags |= TIMER_OF_CLOCK_FREQUENCY;
+	}
+
 	if (to->flags & TIMER_OF_IRQ) {
 		ret = timer_of_irq_init(np, &to->of_irq);
 		if (ret)
@@ -201,6 +227,9 @@ int __init timer_of_init(struct device_node *np, struct timer_of *to)
 	if (flags & TIMER_OF_CLOCK)
 		timer_of_clk_exit(&to->of_clk);
 
+	if (flags & TIMER_OF_CLOCK_FREQUENCY)
+		to->of_clk.rate = 0;
+
 	if (flags & TIMER_OF_BASE)
 		timer_of_base_exit(&to->of_base);
 	return ret;
diff --git a/drivers/clocksource/timer-of.h b/drivers/clocksource/timer-of.h
index a5478f3..a08e108 100644
--- a/drivers/clocksource/timer-of.h
+++ b/drivers/clocksource/timer-of.h
@@ -4,9 +4,10 @@
 
 #include <linux/clockchips.h>
 
-#define TIMER_OF_BASE	0x1
-#define TIMER_OF_CLOCK	0x2
-#define TIMER_OF_IRQ	0x4
+#define TIMER_OF_BASE			0x1
+#define TIMER_OF_CLOCK			0x2
+#define TIMER_OF_IRQ			0x4
+#define TIMER_OF_CLOCK_FREQUENCY	0x8
 
 struct of_timer_irq {
 	int irq;
-- 
2.7.4