From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: rtc-linux@googlegroups.com Received: from mail-out1.kundencontroller.de (mail-out1.kundencontroller.de. [85.31.184.34]) by gmr-mx.google.com with ESMTPS id c135si249246wme.2.2016.07.06.01.43.03 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 Jul 2016 01:43:03 -0700 (PDT) From: Stephan Roslen Subject: [rtc-linux] [PATCH] rtc: sunxi: use external oscillator To: a.zummo@towertech.it, alexandre.belloni@free-electrons.com, maxime.ripard@free-electrons.com, wens@csie.org, rtc-linux@googlegroups.com Message-ID: <577CC494.8020103@roslen.de> Date: Wed, 6 Jul 2016 10:43:00 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Reply-To: rtc-linux@googlegroups.com List-ID: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , 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 --- 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 #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 -- You received this message because you are subscribed to "rtc-linux". Membership options at http://groups.google.com/group/rtc-linux . Please read http://groups.google.com/group/rtc-linux/web/checklist before submitting a driver. --- You received this message because you are subscribed to the Google Groups "rtc-linux" group. To unsubscribe from this group and stop receiving emails from it, send an email to rtc-linux+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.