/* OMAP_RTC_OSC_REG bit fields: */
#define OMAP_RTC_OSC_32KCLK_EN          BIT(6)
#define OMAP_RTC_OSC_SEL_32KCLK_SRC     BIT(3)
#define OMAP_RTC_OSC_OSC32K_GZ_DISABLE  BIT(4)

static int omap_rtc_probe(struct platform_device *pdev)
{
        ...
        rtc->clk = devm_clk_get(&pdev->dev, "ext-clk");
        if (!IS_ERR(rtc->clk))
                rtc->has_ext_clk = true;
        else
                rtc->clk = devm_clk_get(&pdev->dev, "int-clk");
        if (!IS_ERR(rtc->clk))
                clk_prepare_enable(rtc->clk);
        ...
        /* enable RTC functional clock */
        if (rtc->type->has_32kclk_en) {
                reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
                rtc_writel(rtc, OMAP_RTC_OSC_REG, reg | OMAP_RTC_OSC_32KCLK_EN);
        }
        ...
        /* If we have the external clock then switch to it so we can keep ticking across suspend. */
        if (rtc->has_ext_clk) {
                reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
                reg &= ~OMAP_RTC_OSC_OSC32K_GZ_DISABLE;
                reg |= OMAP_RTC_OSC_32KCLK_EN | OMAP_RTC_OSC_SEL_32KCLK_SRC;
                rtc_writel(rtc, OMAP_RTC_OSC_REG, reg);
        }
        ...
}

static int omap_rtc_remove(struct platform_device *pdev)
{
        ...
        if (!IS_ERR(rtc->clk))
                clk_disable_unprepare(rtc->clk);
        ...
        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);
        }
        ...
}

static int __maybe_unused omap_rtc_runtime_suspend(struct device *dev)
{
        ...
        if (rtc->is_suspending && !rtc->has_ext_clk)
                return -EBUSY;
        return 0;
}