On Thu, Nov 03, 2016 at 03:29:24PM +0100, Neil Armstrong wrote:

The Amlogic Meson GX SoCs uses a special register to store the
time in seconds to wakeup after a system suspend.

Where does this register live, exactly? What IP block is it part of?

In order to be able to reuse the RTC wakealarm feature, this
driver implements a fake RTC device which uses the system time
to deduce a suspend delay.

This sounds like an always-on oneshot timer device, not an RTC.

+static int meson_vrtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	unsigned long local_time;
+	struct timeval time;
+
+	do_gettimeofday(&time);
+	local_time = time.tv_sec - (sys_tz.tz_minuteswest * 60);
+	rtc_time_to_tm(local_time, tm);
+
+	return 0;
+}

... if this were a timer, you wouldn't need this hack.

+static int meson_vrtc_probe(struct platform_device *pdev)
+{
+	struct meson_vrtc_data *vrtc;
+	struct resource *res;
+
+	vrtc = devm_kzalloc(&pdev->dev, sizeof(*vrtc), GFP_KERNEL);
+	if (!vrtc)
+		return -ENOMEM;
+
+	vrtc->pdev = pdev;
+
+	/* Alarm registers */
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	vrtc->io_alarm = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(vrtc->io_alarm))
+		return PTR_ERR(vrtc->io_alarm);
+
+	device_init_wakeup(&pdev->dev, 1);
+
+	platform_set_drvdata(pdev, vrtc);
+
+	vrtc->rtc = devm_rtc_device_register(&pdev->dev, "meson-vrtc",
+			&meson_vrtc_ops, THIS_MODULE);
+	if (IS_ERR(vrtc->rtc))
+		return PTR_ERR(vrtc->rtc);
+
+	return 0;
+}

I see that no interrupt is described. How exactly does this wake the system
from suspend? Is there some interrupt managed by FW for this, for example?

+static const struct of_device_id meson_vrtc_dt_match[] = {
+	{ .compatible = "amlogic,meson-vrtc"},

There was no binding documentation in this patch series.

Thanks,
Mark.