[rtc-linux] [PATCH] rtc: sunxi: use external oscillator
From: Stephan Roslen <hidden>
Date: 2016-07-06 08:43:03
Subsystem:
real time clock (rtc) subsystem, the rest · Maintainers:
Alexandre Belloni, Linus Torvalds
We noticed some serious drift problems in Allwinner A20 RTCs. I found out, that the oscillator source needs to be set to an external 32.768 KHz oscillator instead of the internal 32.000 KHz oscillator. Signed-off-by: Stephan Roslen <redacted> --- drivers/rtc/rtc-sunxi.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/drivers/rtc/rtc-sunxi.c b/drivers/rtc/rtc-sunxi.c
index abada60..001256e 100644
--- a/drivers/rtc/rtc-sunxi.c
+++ b/drivers/rtc/rtc-sunxi.c@@ -34,9 +34,19 @@ #include <linux/types.h> #define SUNXI_LOSC_CTRL 0x0000 + +/* magic number required to set bit 0 */ +#define SUNXI_LOSC_CTRL_KEY 0x16AA0000 + +#define SUNXI_LOSC_CTRL_AUTO_SWT_EN BIT(14) + #define SUNXI_LOSC_CTRL_RTC_HMS_ACC BIT(8) #define SUNXI_LOSC_CTRL_RTC_YMD_ACC BIT(7) +#define SUNXI_LOSC_CTRL_EXT_GSM1 BIT(3) +#define SUNXI_LOSC_CTRL_EXT_GSM0 BIT(2) +#define SUNXI_LOSC_CTRL_SRC_SEL BIT(0) + #define SUNXI_RTC_YMD 0x0004 #define SUNXI_RTC_HMS 0x0008
@@ -438,6 +448,8 @@ static int sunxi_rtc_probe(struct platform_device *pdev) struct resource *res; int ret; + uint32_t loscctrl; + chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL); if (!chip) return -ENOMEM;
@@ -468,6 +480,19 @@ static int sunxi_rtc_probe(struct platform_device *pdev) return -ENODEV; } + loscctrl = readl(chip->base + SUNXI_LOSC_CTRL); + loscctrl &= ~(SUNXI_LOSC_CTRL_AUTO_SWT_EN); + loscctrl |= (SUNXI_LOSC_CTRL_SRC_SEL | SUNXI_LOSC_CTRL_KEY); + loscctrl |= SUNXI_LOSC_CTRL_EXT_GSM1; + writel(loscctrl, chip->base + SUNXI_LOSC_CTRL); + udelay(100); + + loscctrl = readl(chip->base + SUNXI_LOSC_CTRL); + if (!(loscctrl & SUNXI_LOSC_CTRL_SRC_SEL)) { + dev_err(&pdev->dev, "Error: Set LOSC to external failed.\n"); + dev_err(&pdev->dev, "Warning: RTC time will be wrong!\n"); + } + /* clear the alarm count value */ writel(0, chip->base + SUNXI_ALRM_DHMS);
--
2.7.4
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