linux-kernel - [PATCH v2 4/9] clocksource: mediatek: Use GPT as sched clock source

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Date:	Sat, 16 May 2015 15:58:25 +0800
From:	Yingjoe Chen <yingjoe.chen@...iatek.com>
To:	Mark Rutland <mark.rutland@....com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Russell King <linux@....linux.org.uk>
CC:	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	<devicetree@...r.kernel.org>, Stephen Boyd <sboyd@...eaurora.org>,
	Pawel Moll <pawel.moll@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	<linux-kernel@...r.kernel.org>,
	Marc Carino <marc.ceeeee@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	<linux-mediatek@...ts.infradead.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	<srv_heupstream@...iatek.com>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH v2 4/9] clocksource: mediatek: Use GPT as sched clock source

When cpu is in deep idle, arch timer will stop counting. Setup GPT as
sched clock source so it can keep counting in idle.

Signed-off-by: Yingjoe Chen <yingjoe.chen@...iatek.com>
---
 drivers/clocksource/mtk_timer.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/clocksource/mtk_timer.c b/drivers/clocksource/mtk_timer.c
index 91206f9..fe7cf72 100644
--- a/drivers/clocksource/mtk_timer.c
+++ b/drivers/clocksource/mtk_timer.c
@@ -24,6 +24,7 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#include <linux/sched_clock.h>
 #include <linux/slab.h>
 
 #define GPT_IRQ_EN_REG		0x00
@@ -59,6 +60,13 @@ struct mtk_clock_event_device {
 	struct clock_event_device dev;
 };
 
+static void __iomem *gpt_base __read_mostly;
+
+static u64 notrace mtk_read_sched_clock(void)
+{
+	return readl_relaxed(gpt_base + TIMER_CNT_REG(GPT_CLK_SRC));
+}
+
 static inline struct mtk_clock_event_device *to_mtk_clk(
 				struct clock_event_device *c)
 {
@@ -243,6 +251,8 @@ static void __init mtk_timer_init(struct device_node *node)
 	mtk_timer_setup(evt, GPT_CLK_SRC, TIMER_CTRL_OP_FREERUN, 1);
 	clocksource_mmio_init(evt->gpt_base + TIMER_CNT_REG(GPT_CLK_SRC),
 			node->name, rate, 300, 32, clocksource_mmio_readl_up);
+	gpt_base = evt->gpt_base;
+	sched_clock_register(mtk_read_sched_clock, 32, rate);
 
 	/* Configure clock event */
 	mtk_timer_setup(evt, GPT_CLK_EVT, TIMER_CTRL_OP_REPEAT, 0);
-- 
1.8.1.1.dirty

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