dm: x86: Allow TSC timer to be used before DM is ready

With bootstage we need access to the timer before driver model is set up.
To handle this, put the required state in global_data and provide a new
function to set up the device, separate from the driver's probe() method.

This will be used by the 'early' timer also.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/include/asm/global_data.h

@@ -77,6 +77,7 @@ struct arch_global_data {
 	uint8_t x86_mask;
 	uint32_t x86_device;
 	uint64_t tsc_base;		/* Initial value returned by rdtsc() */
+	unsigned long clock_rate;	/* Clock rate of timer in Hz */
 	void *new_fdt;			/* Relocated FDT */
 	uint32_t bist;			/* Built-in self test value */
 	enum pei_boot_mode_t pei_boot_mode;

drivers/timer/tsc_timer.c

@@ -331,17 +331,17 @@ static int tsc_timer_get_count(struct udevice *dev, u64 *count)
 	return 0;
 }
 
-static int tsc_timer_probe(struct udevice *dev)
+static void tsc_timer_ensure_setup(void)
 {
-	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
-
+	if (gd->arch.tsc_base)
+		return;
 	gd->arch.tsc_base = rdtsc();
 
 	/*
 	 * If there is no clock frequency specified in the device tree,
 	 * calibrate it by ourselves.
 	 */
-	if (!uc_priv->clock_rate) {
+	if (!gd->arch.clock_rate) {
 		unsigned long fast_calibrate;
 
 		fast_calibrate = cpu_mhz_from_msr();
@@ -351,12 +351,32 @@ static int tsc_timer_probe(struct udevice *dev)
 				panic("TSC frequency is ZERO");
 		}
 
-		uc_priv->clock_rate = fast_calibrate * 1000000;
+		gd->arch.clock_rate = fast_calibrate * 1000000;
 	}
+}
+
+static int tsc_timer_probe(struct udevice *dev)
+{
+	struct timer_dev_priv *uc_priv = dev_get_uclass_priv(dev);
+
+	tsc_timer_ensure_setup();
+	uc_priv->clock_rate = gd->arch.clock_rate;
 
 	return 0;
 }
 
+unsigned long notrace timer_early_get_rate(void)
+{
+	tsc_timer_ensure_setup();
+
+	return gd->arch.clock_rate;
+}
+
+u64 notrace timer_early_get_count(void)
+{
+	return rdtsc() - gd->arch.tsc_base;
+}
+
 static const struct timer_ops tsc_timer_ops = {
 	.get_count = tsc_timer_get_count,
 };