soc/mediatek: Add early_init for passing data across stages

Add support for "early_init_data" region, which can be used to store
data initialized in an early stage (such as bootblock), and retrieve it
in later stages (such as ramstage).

TEST=Build pass and boot up to kernel successfully via SSD on Dojo
board, here is the SSD information in boot log:
 == NVME IDENTIFY CONTROLLER DATA ==
    PCI VID   : 0x15b7
    PCI SSVID : 0x15b7
    SN        : 21517J440114
    MN        : WDC PC SN530 SDBPTPZ-256G-1006
    RAB       : 0x4
    AERL      : 0x7
    SQES      : 0x66
    CQES      : 0x44
    NN        : 0x1
Identified NVMe model WDC PC SN530 SDBPTPZ-256G-1006

BUG=b:178565024
BRANCH=cherry

Signed-off-by: Jianjun Wang <jianjun.wang@mediatek.com>
Change-Id: I01f91b7fe2cbe4f73b5c616bb7aae778dee27d9a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63019
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>

src/soc/mediatek/common/early_init.c

@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <assert.h>
+#include <soc/early_init.h>
+#include <stdlib.h>
+#include <string.h>
+
+static struct early_init_data *find_early_init(void)
+{
+	assert(sizeof(struct early_init_data) <= REGION_SIZE(early_init_data));
+	return (struct early_init_data *)_early_init_data;
+}
+
+void early_init_clear(void)
+{
+	struct early_init_data *data = find_early_init();
+
+	if (!data)
+		return;
+
+	memset(data, 0, sizeof(*data));
+}
+
+void early_init_save_time(enum early_init_type init_type)
+{
+	struct early_init_data *data = find_early_init();
+
+	if (!data)
+		return;
+
+	timer_monotonic_get(&data->init_time[init_type]);
+}
+
+uint64_t early_init_get_elapsed_time_us(enum early_init_type init_type)
+{
+	struct early_init_data *data = find_early_init();
+	struct mono_time cur_time;
+
+	if (!data)
+		return 0;
+
+	memset(&cur_time, 0, sizeof(cur_time));
+
+	/* If early init data was never saved */
+	if (!memcmp(&data->init_time[init_type], &cur_time, sizeof(cur_time)))
+		return 0;
+
+	timer_monotonic_get(&cur_time);
+
+	return mono_time_diff_microseconds(&data->init_time[init_type],
+					   &cur_time);
+}

src/soc/mediatek/common/include/soc/early_init.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef SOC_MEDIATEK_EARLY_INIT_H
+#define SOC_MEDIATEK_EARLY_INIT_H
+
+#include <soc/symbols.h>
+#include <stdint.h>
+#include <symbols.h>
+#include <timer.h>
+
+DECLARE_REGION(early_init_data);
+
+enum early_init_type {
+	EARLY_INIT_PCIE,
+	EARLY_INIT_MAX,
+};
+
+struct early_init_data {
+	struct mono_time init_time[EARLY_INIT_MAX];
+};
+
+void early_init_clear(void);
+void early_init_save_time(enum early_init_type init_type);
+uint64_t early_init_get_elapsed_time_us(enum early_init_type init_type);
+
+#endif /* SOC_MEDIATEK_EARLY_INIT_H */