diff mbox series

[07/25] clocksource/drivers/meson6_timer: Implement the ARM delay timer

Message ID 20181218212844.30445-7-daniel.lezcano@linaro.org (mailing list archive)
State Not Applicable
Headers show
Series None | expand

Commit Message

Daniel Lezcano Dec. 18, 2018, 9:28 p.m. UTC
From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

Implement an ARM delay timer to be used for udelay(). This allows us to
skip the delay loop calibration at boot.

With this patch udelay() is now independent of CPU frequency changes.
This is a good thing on Meson8, Meson8b and Meson8m2 because changing
the CPU frequency requires running the CPU clock off the XTAL while
changing the PLL or it's dividers. After changing the CPU clocks we need
to wait a few usecs for the clock to become stable. So having an
udelay() implementation that doesn't depend on the CPU frequency is

Suggested-by: Jianxin Pan <jianxin.pan@amlogic.com>
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
 drivers/clocksource/meson6_timer.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
diff mbox series


diff --git a/drivers/clocksource/meson6_timer.c b/drivers/clocksource/meson6_timer.c
index 23c7638e2bb3..84bd9479c3f8 100644
--- a/drivers/clocksource/meson6_timer.c
+++ b/drivers/clocksource/meson6_timer.c
@@ -22,6 +22,10 @@ 
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#ifdef CONFIG_ARM
+#include <linux/delay.h>
 #define MESON_ISA_TIMER_MUX					0x00
@@ -54,6 +58,18 @@ 
 static void __iomem *timer_base;
+#ifdef CONFIG_ARM
+static unsigned long meson6_read_current_timer(void)
+	return readl_relaxed(timer_base + MESON_ISA_TIMERE);
+static struct delay_timer meson6_delay_timer = {
+	.read_current_timer = meson6_read_current_timer,
+	.freq = 1000 * 1000,
 static u64 notrace meson6_timer_sched_read(void)
 	return (u64)readl(timer_base + MESON_ISA_TIMERE);
@@ -192,6 +208,12 @@  static int __init meson6_timer_init(struct device_node *node)
 	clockevents_config_and_register(&meson6_clockevent, USEC_PER_SEC,
 					1, 0xfffe);
+#ifdef CONFIG_ARM
+	/* Also use MESON_ISA_TIMERE for delays */
+	register_current_timer_delay(&meson6_delay_timer);
 	return 0;
 TIMER_OF_DECLARE(meson6, "amlogic,meson6-timer",