rockchip: timer: implement timer_get_boot_us

To make the Rockchip DM timer driver useful for the timing of
bootstages, we need a few enhancements:
 - This implements timer_get_boot_us.
 - This avoids reinitialising the timer, if it has already been
   set up (e.g. by our TPL and SPL stages). Now, we have a single
   timebase ticking from TPL through the full U-Boot.
 - This adds support for reading the timer even before the
   device-model is ready: we find the timer via /chosen/tick-timer,
   then read its address and clock-frequency, and finally read the
   timeval directly).

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>

drivers/timer/rockchip_timer.c

@@ -6,6 +6,7 @@
 
 #include <common.h>
 #include <dm.h>
+#include <dm/ofnode.h>
 #include <mapmem.h>
 #include <asm/arch/timer.h>
 #include <dt-structs.h>
@@ -25,17 +26,72 @@ struct rockchip_timer_priv {
 	struct rk_timer *timer;
 };
 
-static int rockchip_timer_get_count(struct udevice *dev, u64 *count)
+static inline int64_t rockchip_timer_get_curr_value(struct rk_timer *timer)
 {
-	struct rockchip_timer_priv *priv = dev_get_priv(dev);
 	uint64_t timebase_h, timebase_l;
 	uint64_t cntr;
 
-	timebase_l = readl(&priv->timer->timer_curr_value0);
-	timebase_h = readl(&priv->timer->timer_curr_value1);
+	timebase_l = readl(&timer->timer_curr_value0);
+	timebase_h = readl(&timer->timer_curr_value1);
 
-	/* timers are down-counting */
 	cntr = timebase_h << 32 | timebase_l;
+	return cntr;
+}
+
+#if CONFIG_IS_ENABLED(BOOTSTAGE)
+ulong timer_get_boot_us(void)
+{
+	uint64_t  ticks = 0;
+	uint32_t  rate;
+	uint64_t  us;
+	int ret;
+
+	ret = dm_timer_init();
+
+	if (!ret) {
+		/* The timer is available */
+		rate = timer_get_rate(gd->timer);
+		timer_get_count(gd->timer, &ticks);
+#if !CONFIG_IS_ENABLED(OF_PLATDATA)
+	} else if (ret == -EAGAIN) {
+		/* We have been called so early that the DM is not ready,... */
+		ofnode node = offset_to_ofnode(-1);
+		struct rk_timer *timer = NULL;
+
+		/*
+		 * ... so we try to access the raw timer, if it is specified
+		 * via the tick-timer property in /chosen.
+		 */
+		node = ofnode_get_chosen_node("tick-timer");
+		if (!ofnode_valid(node)) {
+			debug("%s: no /chosen/tick-timer\n", __func__);
+			return 0;
+		}
+
+		timer = (struct rk_timer *)ofnode_get_addr(node);
+
+		/* This timer is down-counting */
+		ticks = ~0uLL - rockchip_timer_get_curr_value(timer);
+		if (ofnode_read_u32(node, "clock-frequency", &rate)) {
+			debug("%s: could not read clock-frequency\n", __func__);
+			return 0;
+		}
+#endif
+	} else {
+		return 0;
+	}
+
+	us = (ticks * 1000) / rate;
+	return us;
+}
+#endif
+
+static int rockchip_timer_get_count(struct udevice *dev, u64 *count)
+{
+	struct rockchip_timer_priv *priv = dev_get_priv(dev);
+	uint64_t cntr = rockchip_timer_get_curr_value(priv->timer);
+
+	/* timers are down-counting */
 	*count = ~0ull - cntr;
 	return 0;
 }
@@ -58,6 +114,12 @@ static int rockchip_timer_start(struct udevice *dev)
 	const uint32_t reload_val_l = reload_val & 0xffffffff;
 	const uint32_t reload_val_h = reload_val >> 32;
 
+	/* don't reinit, if the timer is already running and set up */
+	if ((readl(&priv->timer->timer_ctrl_reg) & 1) == 1 &&
+	    (readl(&priv->timer->timer_load_count0) == reload_val_l) &&
+	    (readl(&priv->timer->timer_load_count1) == reload_val_h))
+		return 0;
+
 	/* disable timer and reset all control */
 	writel(0, &priv->timer->timer_ctrl_reg);
 	/* write reload value */