[PATCH 2/2] rtc: omap: Add external clock enabling support

[Keerthy <j-keerthy@xxxxxx>]

Configure the clock source to either internal clock
or external clock based on the availability of the clocks.
External clock is preferred as it can be ticking during suspend.

Signed-off-by: Keerthy <j-keerthy@xxxxxx>
---
 drivers/rtc/rtc-omap.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/drivers/rtc/rtc-omap.c b/drivers/rtc/rtc-omap.c
index 8b6355f..479f730 100644
--- a/drivers/rtc/rtc-omap.c
+++ b/drivers/rtc/rtc-omap.c
@@ -25,6 +25,7 @@
 #include <linux/of_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/io.h>
+#include <linux/clk.h>
 
 /*
  * The OMAP RTC is a year/month/day/hours/minutes/seconds BCD clock
@@ -107,6 +108,7 @@
 
 /* OMAP_RTC_OSC_REG bit fields: */
 #define OMAP_RTC_OSC_32KCLK_EN		BIT(6)
+#define OMAP_RTC_OSC_SEL_32KCLK_SRC	BIT(3)
 
 /* OMAP_RTC_IRQWAKEEN bit fields: */
 #define OMAP_RTC_IRQWAKEEN_ALARM_WAKEEN	BIT(1)
@@ -136,6 +138,7 @@ struct omap_rtc {
 	int irq_timer;
 	u8 interrupts_reg;
 	bool is_pmic_controller;
+	bool has_ext_clk;
 	const struct omap_rtc_device_type *type;
 };
 
@@ -525,6 +528,7 @@ static int omap_rtc_probe(struct platform_device *pdev)
 {
 	struct omap_rtc	*rtc;
 	struct resource	*res;
+	struct clk *ext_clk, *int_clk;
 	u8 reg, mask, new_ctrl;
 	const struct platform_device_id *id_entry;
 	const struct of_device_id *of_id;
@@ -553,6 +557,17 @@ static int omap_rtc_probe(struct platform_device *pdev)
 	if (rtc->irq_alarm <= 0)
 		return -ENOENT;
 
+	ext_clk = devm_clk_get(&pdev->dev, "ext-clk");
+	if (!IS_ERR(ext_clk)) {
+		rtc->has_ext_clk = true;
+		clk_prepare(ext_clk);
+	} else {
+		int_clk = devm_clk_get(&pdev->dev, "int-clk");
+
+		if (!IS_ERR(int_clk))
+			clk_prepare(int_clk);
+	}
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	rtc->base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(rtc->base))
@@ -627,6 +642,17 @@ static int omap_rtc_probe(struct platform_device *pdev)
 	if (reg != new_ctrl)
 		rtc_write(rtc, OMAP_RTC_CTRL_REG, new_ctrl);
 
+	/*
+	 * If we have the external clock then
+	 * Switch to external clock so we can keep ticking
+	 * acorss suspend
+	 */
+	if (rtc->has_ext_clk) {
+		reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
+		rtc_write(rtc, OMAP_RTC_OSC_REG, reg |
+			  OMAP_RTC_OSC_SEL_32KCLK_SRC);
+	}
+
 	rtc->type->lock(rtc);
 
 	device_init_wakeup(&pdev->dev, true);
@@ -672,6 +698,8 @@ err:
 static int __exit omap_rtc_remove(struct platform_device *pdev)
 {
 	struct omap_rtc *rtc = platform_get_drvdata(pdev);
+	struct clk *ext_clk, *int_clk;
+	u8 reg;
 
 	if (pm_power_off == omap_rtc_power_off &&
 			omap_rtc_power_off_rtc == rtc) {
@@ -681,10 +709,26 @@ static int __exit omap_rtc_remove(struct platform_device *pdev)
 
 	device_init_wakeup(&pdev->dev, 0);
 
+	ext_clk = devm_clk_get(&pdev->dev, "ext-clk");
+	if (!IS_ERR(ext_clk)) {
+		clk_unprepare(ext_clk);
+	} else {
+		int_clk = devm_clk_get(&pdev->dev, "int-clk");
+
+		if (!IS_ERR(int_clk))
+			clk_unprepare(int_clk);
+	}
+
 	rtc->type->unlock(rtc);
 	/* leave rtc running, but disable irqs */
 	rtc_write(rtc, OMAP_RTC_INTERRUPTS_REG, 0);
 
+	if (rtc->has_ext_clk) {
+		reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
+		reg &= ~OMAP_RTC_OSC_SEL_32KCLK_SRC;
+		rtc_write(rtc, OMAP_RTC_OSC_REG, reg);
+	}
+
 	rtc->type->lock(rtc);
 
 	/* Disable the clock/module */
-- 
1.9.1

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