[PATCH 1/5] drivers/rtc/rtc-xgene: Add prescaler support in APM X-Gene RTC driver

[wefu at redhat.com]

From: Wei Fu <wefu at redhat.com>

This patch add Counter Prescaler support in APM X-Gene RTC driver by
getting prescaler (Optional) property value from dtb.

Signed-off-by: Wei Fu <wefu at redhat.com>
---
 drivers/rtc/Kconfig     | 10 ++++++++++
 drivers/rtc/rtc-xgene.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index c63e32d012f2..3a89f1e6095d 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -1888,6 +1888,16 @@ config RTC_DRV_XGENE
 	  This driver can also be built as a module, if so, the module
 	  will be called "rtc-xgene".
 
+config RTC_DRV_XGENE_PRESCALER
+	bool "Pre-scaler Counter support for APM X-Gene RTC driver"
+	depends on RTC_DRV_XGENE
+	depends on ARCH_THEAD
+	default y
+	help
+	  Say Y here if your Soc has Pre-scaler Counter support on rtc-xgene.
+
+	  This hardware support can only be found in DW_apb_rtc after v2.06a.
+
 config RTC_DRV_PIC32
 	tristate "Microchip PIC32 RTC"
 	depends on MACH_PIC32
diff --git a/drivers/rtc/rtc-xgene.c b/drivers/rtc/rtc-xgene.c
index f78efc9760c0..4d6f1629b973 100644
--- a/drivers/rtc/rtc-xgene.c
+++ b/drivers/rtc/rtc-xgene.c
@@ -26,11 +26,13 @@
 #define  RTC_CCR_MASK		BIT(1)
 #define  RTC_CCR_EN		BIT(2)
 #define  RTC_CCR_WEN		BIT(3)
+#define  RTC_CCR_PSCLR_EN	BIT(4)
 #define RTC_STAT		0x10
 #define  RTC_STAT_BIT		BIT(0)
 #define RTC_RSTAT		0x14
 #define RTC_EOI			0x18
 #define RTC_VER			0x1C
+#define RTC_CPSR		0x20
 
 struct xgene_rtc_dev {
 	struct rtc_device *rtc;
@@ -40,6 +42,33 @@ struct xgene_rtc_dev {
 	unsigned int irq_enabled;
 };
 
+static void xgene_rtc_set_prescaler(struct device *dev)
+{
+#ifdef CONFIG_RTC_DRV_XGENE_PRESCALER
+	u32 ccr;
+	u32 prescaler;
+	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
+
+	if (device_property_read_u32(dev, "prescaler", &prescaler)) {
+		dev_warn(dev, "Missing the pre-scaler config for RTC.\n");
+		dev_warn(dev, "The current pre-scaler config is 0x%x.\n",
+			 readl(pdata->csr_base + RTC_CPSR));
+		return;
+	}
+
+	/* The clock source on some platform to RTC is NOT 1HZ,
+	 * so we need to prescale the clock to make the input clock become 1HZ,
+	 * like (clock_source/prescaler) = 1HZ
+	 */
+	writel(prescaler, pdata->csr_base + RTC_CPSR);
+
+	/* enable RTC Prescaler feature in CCR register */
+	ccr = readl(pdata->csr_base + RTC_CCR);
+	ccr |= RTC_CCR_PSCLR_EN;
+	writel(ccr, pdata->csr_base + RTC_CCR);
+#endif /* CONFIG_RTC_DRV_XGENE_PRESCALER */
+}
+
 static int xgene_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct xgene_rtc_dev *pdata = dev_get_drvdata(dev);
@@ -174,6 +203,8 @@ static int xgene_rtc_probe(struct platform_device *pdev)
 	/* Turn on the clock and the crystal */
 	writel(RTC_CCR_EN, pdata->csr_base + RTC_CCR);
 
+	xgene_rtc_set_prescaler(&pdev->dev);
+
 	ret = device_init_wakeup(&pdev->dev, 1);
 	if (ret) {
 		clk_disable_unprepare(pdata->clk);
-- 
2.44.0