[PATCH 4/9] MXS/i.MX28: there is more than one way to clock the RTC

[Shawn Guo]

On Mon, Mar 04, 2013 at 03:05:43PM +0100, Steffen Trumtrar wrote:
> From: Juergen Beisert <jbe at pengutronix.de>
> 
> Reflect the possibilities via device tree and configure the RTC correctly
> 
> Signed-off-by: Juergen Beisert <jbe at pengutronix.de>
> Signed-off-by: Steffen Trumtrar <s.trumtrar at pengutronix.de>
> ---
>  arch/arm/boot/dts/imx28.dtsi |    2 ++
>  drivers/rtc/rtc-stmp3xxx.c   |   76 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 78 insertions(+)
> 
> diff --git a/arch/arm/boot/dts/imx28.dtsi b/arch/arm/boot/dts/imx28.dtsi
> index dcd0844..d89af79 100644
> --- a/arch/arm/boot/dts/imx28.dtsi
> +++ b/arch/arm/boot/dts/imx28.dtsi
> @@ -818,6 +818,8 @@
>  				compatible = "fsl,imx28-rtc", "fsl,stmp3xxx-rtc";
>  				reg = <0x80056000 0x2000>;
>  				interrupts = <29>;
> +				clocks = <&clks 65>, <&clks 40> ;
> +				clock-names = "32k", "24m";

The changes should be in some mxs/arch patch.

>  			};
>  
>  			i2c0: i2c at 80058000 {
> diff --git a/drivers/rtc/rtc-stmp3xxx.c b/drivers/rtc/rtc-stmp3xxx.c
> index 7311292..fb4b823 100644
> --- a/drivers/rtc/rtc-stmp3xxx.c
> +++ b/drivers/rtc/rtc-stmp3xxx.c
> @@ -21,6 +21,7 @@
>  #include <linux/module.h>
>  #include <linux/io.h>
>  #include <linux/init.h>
> +#include <linux/clk.h>
>  #include <linux/platform_device.h>
>  #include <linux/interrupt.h>
>  #include <linux/rtc.h>
> @@ -176,11 +177,55 @@ static irqreturn_t stmp3xxx_rtc_interrupt(int irq, void *dev_id)
>  	return IRQ_NONE;
>  }
>  
> +/*
> + * To keep the energy consumption low, keep only
> + * the really used oscillator running when the power is down
> + */
> +static void stmp3xxx_alarm_keep_oscillator(const struct stmp3xxx_rtc_data *rtc_data)
> +{
> +	switch (rtc_data->clk_src) {
> +	case MXS_OSC_24M:
> +		/* keep the 24 MHz oscillator running even in power down */
> +		writel(STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ | /* 24 MHz / 750 */
> +			STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP,
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
> +		writel(STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
> +			STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE,
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
> +		break;
> +	case MXS_OSC_32K:
> +		/* keep the 32 kHz oscillator running even in power down */
> +		writel(STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ | /* 32 kHz */
> +			STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
> +			STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE,
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
> +		writel(STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP,
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
> +		break;
> +	case MXS_OSC_32K768:
> +		/* keep the 32 kHz oscillator running even in power down */
> +		writel(STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
> +			STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE,
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
> +		writel(STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ | /* 32.768 kHz */
> +			STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP,
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
> +		break;
> +	case MXS_UNKNOWN:
> +	default:
> +		break;
> +	}
> +}
> +
>  static int stmp3xxx_alarm_irq_enable(struct device *dev, unsigned int enabled)
>  {
>  	struct stmp3xxx_rtc_data *rtc_data = dev_get_drvdata(dev);
>  
> +	stmp3xxx_alarm_keep_oscillator(rtc_data);
> +
>  	if (enabled) {
> +		writel(STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE, /* to be able to sleep */
> +			rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
>  		writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
>  				STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN,
>  				rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
> @@ -248,6 +293,8 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
>  {
>  	struct stmp3xxx_rtc_data *rtc_data;
>  	struct resource *r;
> +	struct clk *clk;
> +	unsigned long rate;
>  	int err;
>  
>  	rtc_data = kzalloc(sizeof *rtc_data, GFP_KERNEL);
> @@ -280,6 +327,35 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, rtc_data);
>  
>  	mxs_reset_block(rtc_data->io);
> +
> +	/*
> +	 * configure the RTC to provide the correct time
> +	 */
> +	clk = clk_get(&pdev->dev, "32k");

devm_clk_get

Shawn

> +	if (IS_ERR(clk)) {
> +		/* just a fall back */
> +		dev_warn(&pdev->dev, "RTC's input clock undefined\n");
> +		rtc_data->clk_src = MXS_OSC_24M;
> +	} else {
> +		rate = clk_get_rate(clk);
> +		if (rate == 0) {
> +			/* no dedicated external crystal */
> +			rtc_data->clk_src = MXS_OSC_24M;
> +			dev_info(&pdev->dev, "Using 24 MHz as RTC's clock\n");
> +		} else if (rate == 32000) {
> +			rtc_data->clk_src = MXS_OSC_32K;
> +			dev_info(&pdev->dev, "Using 32.0 kHz as RTC's clock\n");
> +		} else if (rate == 32768) {
> +			rtc_data->clk_src = MXS_OSC_32K768;
> +			dev_info(&pdev->dev, "Using 32.768 kHz as RTC's clock\n");
> +		} else
> +			dev_warn(&pdev->dev,
> +				"Cannot init the RTC's clock source\n");
> +	}
> +
> +	/* basically configure the RTC's input clock */
> +	stmp3xxx_alarm_keep_oscillator(rtc_data);
> +
>  	writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
>  			STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN |
>  			STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE,
> -- 
> 1.7.10.4
>