soc/mediatek/mt8195: add mt6691 driver

Add mt6691 buck control for DRAM to run fast calibration test.
It is needed to get and set voltage during testing.

Signed-off-by: Henry Chen <henryc.chen@mediatek.com>
Change-Id: I4fb9f7245d44383a6a3a0cf8d00f7f503cbdeb06
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55575
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/mediatek/mt8195/Makefile.inc

@@ -45,6 +45,7 @@ romstage-y += ../common/pmif_spi.c pmif_spi.c
 romstage-y += ../common/pmif_spmi.c pmif_spmi.c
 romstage-y += ../common/mt6315.c mt6315.c
 romstage-y += ../common/mt6359p.c mt6359p.c
+romstage-y += mt6691.c
 romstage-y += ../common/rtc.c ../common/rtc_osc_init.c ../common/rtc_mt6359p.c
 
 ramstage-y += ../common/auxadc.c

src/soc/mediatek/mt8195/include/soc/mt6691.h

@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __SOC_MEDIATEK_MT8195_MT6691_H__
+#define __SOC_MEDIATEK_MT8195_MT6691_H__
+
+#include <stdint.h>
+
+void mt6691_probe(uint8_t i2c_num);
+int mt6691_set_voltage(uint8_t i2c_num, unsigned int volt_uv);
+int mt6691_get_voltage(uint8_t i2c_num);
+
+#define MT6691_CID_CODE		0x01
+
+#define MT6691_VDD2_ID		0x0000
+#define MT6691_VDDQ_ID		0x0000
+#define MT6691_PGOOD_SHIFT	7
+#define MT6691_DN_SR_MASK	0x7
+#define MT6691_DN_SR_SHIFT	5
+
+enum {
+	/* Voltage setting */
+	MT6691_VSEL0 =		0x00,
+	MT6691_VSEL1 =		0x01,
+	/* Control register */
+	MT6691_CONTROL =	0x02,
+	/* IC Type */
+	MT6691_ID1 =		0x03,
+	/* IC mask version */
+	MT6691_ID2 =		0x04,
+	/* Monitor register */
+	MT6691_MONITOR =	0x05,
+	MT6691_CTRL2 =		0x06,
+	MT6691_CTRL3 =		0x07,
+	MT6691_CTRL4 =		0x08,
+};
+
+#endif

src/soc/mediatek/mt8195/mt6691.c

@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <console/console.h>
+#include <device/i2c_simple.h>
+#include <soc/mt6691.h>
+
+#define MT6691_MIN_VOLTAGE		300000
+#define MT6691_MAX_VOLTAGE		1300000
+#define MT6691_STEP_UV			5000
+
+enum {
+	MT6691_SLAVE_ADDR = 0x51,
+};
+
+int mt6691_set_voltage(uint8_t i2c_num, unsigned int volt_uv)
+{
+	uint8_t selector;
+
+	if (volt_uv > MT6691_MAX_VOLTAGE || volt_uv < MT6691_MIN_VOLTAGE) {
+		printk(BIOS_ERR, "%s: voltage out of range\n", __func__);
+		return -1;
+	}
+
+	selector = DIV_ROUND_UP(volt_uv - MT6691_MIN_VOLTAGE, MT6691_STEP_UV);
+
+	return i2c_write_field(i2c_num, MT6691_SLAVE_ADDR,
+			       MT6691_VSEL0, selector, 0xFF, 0);
+}
+
+int mt6691_get_voltage(uint8_t i2c_num)
+{
+	uint8_t selector = 0;
+	unsigned int volt;
+
+	if (i2c_read_field(i2c_num, MT6691_SLAVE_ADDR, MT6691_VSEL0,
+			   &selector, 0xFF, 0) < 0) {
+		printk(BIOS_ERR, "%s: failed to get voltage from i2c\n", __func__);
+		return -1;
+	}
+
+	volt = (selector * MT6691_STEP_UV) + MT6691_MIN_VOLTAGE;
+
+	if (volt > MT6691_MAX_VOLTAGE) {
+		printk(BIOS_ERR, "%s: voltage out of range\n", __func__);
+		return -1;
+	}
+
+	return volt;
+}
+
+static uint8_t get_mt6691_chip_id(uint8_t i2c_num)
+{
+	uint8_t id;
+
+	if (i2c_read_field(i2c_num, MT6691_SLAVE_ADDR, MT6691_MONITOR,
+			   &id, 0x1, MT6691_PGOOD_SHIFT) < 0) {
+		printk(BIOS_ERR, "%s: failed to read from i2c", __func__);
+		return 0;
+	}
+
+	return id;
+}
+
+void mt6691_probe(uint8_t i2c_num)
+{
+	/* Check device ID is MT6691 */
+	if (!get_mt6691_chip_id(i2c_num)) {
+		printk(BIOS_ERR, "ERROR: unknown MT6691 chip_id\n");
+		return;
+	}
+	/* Slew rate 12mV */
+	i2c_write_field(i2c_num, MT6691_SLAVE_ADDR, MT6691_CTRL2, 0x1,
+			MT6691_DN_SR_MASK, MT6691_DN_SR_SHIFT);
+}