linux-kernel - [PATCH V5 1/5] clocksource: imx-sysctr: Add internal clock divider handle

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Date:   Wed, 10 Jul 2019 14:30:52 +0800
From:   Anson.Huang@....com
To:     catalin.marinas@....com, will@...nel.org, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        daniel.lezcano@...aro.org, tglx@...utronix.de,
        leonard.crestez@....com, aisheng.dong@....com,
        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-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Cc:     Linux-imx@....com
Subject: [PATCH V5 1/5] clocksource: imx-sysctr: Add internal clock divider handle

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

The system counter block guide states that the base clock is
internally divided by 3 before use, that means the clock input of
system counter defined in DT should be base clock which is normally
from OSC, and then internally divided by 3 before use.

Signed-off-by: Anson Huang <Anson.Huang@....com>
---
Changes since V4:
	- to solve the clock driver probed after system counter driver issue, now we can easily switch to
	  use fixed clock defined in DT and get its rate, then divided by 3 to get real clock rate for
	  system counter driver, no need to add "clock-frequency" property in DT.
---
 drivers/clocksource/timer-imx-sysctr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/clocksource/timer-imx-sysctr.c b/drivers/clocksource/timer-imx-sysctr.c
index fd7d680..b7c80a3 100644
--- a/drivers/clocksource/timer-imx-sysctr.c
+++ b/drivers/clocksource/timer-imx-sysctr.c
@@ -20,6 +20,8 @@
 #define SYS_CTR_EN		0x1
 #define SYS_CTR_IRQ_MASK	0x2
 
+#define SYS_CTR_CLK_DIV		0x3
+
 static void __iomem *sys_ctr_base;
 static u32 cmpcr;
 
@@ -134,6 +136,9 @@ static int __init sysctr_timer_init(struct device_node *np)
 	if (ret)
 		return ret;
 
+	/* system counter clock is divided by 3 internally */
+	to_sysctr.of_clk.rate /= SYS_CTR_CLK_DIV;
+
 	sys_ctr_base = timer_of_base(&to_sysctr);
 	cmpcr = readl(sys_ctr_base + CMPCR);
 	cmpcr &= ~SYS_CTR_EN;
-- 
2.7.4