drivers/i2c: Add a new RTC RV-3028-C7 from Micro Crystal

This patch adds a driver for a new RTC from Micro Crystal. Supported
features are:
 * configure backup voltage switchover via devicetree
 * configure backup capacitor charging mode via devicetree
 * set date if a voltage drop on backup voltage was detected
   to either a user definable (devicetree) or coreboot build date

Change-Id: I37176ea726e50e4e74d409488981d7618ecff8bb
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67099
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>

1 files changed, 194 insertions, 0 deletions

diff --git a/src/drivers/i2c/rv3028c7/rv3028c7.c b/src/drivers/i2c/rv3028c7/rv3028c7.c
new file mode 100644
index 0000000000..e7e3b47ece
--- /dev/null
+++ b/src/drivers/i2c/rv3028c7/rv3028c7.c
@@ -0,0 +1,194 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <commonlib/bsd/bcd.h>
+#include <console/console.h>
+#include <delay.h>
+#include <device/device.h>
+#include <device/i2c.h>
+#include <device/i2c_bus.h>
+#include <timer.h>
+#include <types.h>
+#include <version.h>
+#include "chip.h"
+#include "rv3028c7.h"
+
+static enum cb_err rtc_eep_wait_ready(struct device *dev)
+{
+	struct stopwatch sw;
+	uint8_t status;
+
+	stopwatch_init_msecs_expire(&sw, EEP_SYNC_TIMEOUT_MS);
+	do {
+		status = (uint8_t)i2c_dev_readb_at(dev, STATUS_REG);
+		mdelay(1);
+	} while ((status & EE_BUSY_BIT) && !stopwatch_expired(&sw));
+
+	if (status & EE_BUSY_BIT) {
+		return CB_ERR;
+	} else {
+		return CB_SUCCESS;
+	}
+}
+
+static enum cb_err rtc_eep_auto_refresh(struct device *dev, uint8_t state)
+{
+	uint8_t reg;
+
+	reg = (uint8_t)i2c_dev_readb_at(dev, CTRL1_REG);
+	reg &= ~EERD_BIT;
+	if (state == EEP_REFRESH_DIS)
+		reg |= EERD_BIT;
+	i2c_dev_writeb_at(dev, CTRL1_REG, reg);
+	/* Wait until the EEPROM has finished a possible running operation. */
+	if (rtc_eep_wait_ready(dev) != CB_SUCCESS) {
+		printk(BIOS_ERR, "%s: EEPROM access timed out (%d ms)!\n",
+			dev->chip_ops->name, EEP_SYNC_TIMEOUT_MS);
+		return CB_ERR;
+	}
+	return CB_SUCCESS;
+}
+
+static enum cb_err rtc_eep_start_update(struct device *dev)
+{
+	/* Disable EEPROM auto refresh before writing RAM to EEPROM
+	   to avoid race conditions. */
+	if (rtc_eep_auto_refresh(dev, EEP_REFRESH_DIS))
+		return CB_ERR;
+
+	/* Now start the update cycle.*/
+	i2c_dev_writeb_at(dev, EEP_CMD_REG, EEP_CMD_PREFIX);
+	i2c_dev_writeb_at(dev, EEP_CMD_REG, EEP_CMD_UPDATE);
+	return CB_SUCCESS;
+}
+
+static void rtc_set_time_date(struct device *dev)
+{
+	struct drivers_i2c_rv3028c7_config *config = dev->chip_info;
+	uint8_t buf[7];
+
+	/* The buffer contains the seconds through years of the new time and date.
+	   Whenever a new date is set, the time is set to 00:00:00. */
+	buf[0] = 0;	/* Entry for seconds. */
+	buf[1] = 0;	/* Entry for minutes. */
+	buf[2] = 0;	/* Entry for hours. */
+	if (config->set_user_date) {
+		buf[3] = config->user_weekday;
+		buf[4] = bin2bcd(config->user_day);
+		buf[5] = bin2bcd(config->user_month);
+		buf[6] = bin2bcd(config->user_year);
+		printk(BIOS_DEBUG, "%s: Set to user date\n", dev->chip_ops->name);
+	} else {
+		buf[3] = coreboot_build_date.weekday;
+		buf[4] = coreboot_build_date.day;
+		buf[5] = coreboot_build_date.month;
+		buf[6] = coreboot_build_date.year;
+		printk(BIOS_DEBUG, "%s: Set to coreboot build date\n", dev->chip_ops->name);
+	}
+	/* According to the datasheet, date and time should be transferred in "one go"
+	   in order to avoid value corruption. */
+	if (i2c_dev_write_at(dev, buf, sizeof(buf), 0) != sizeof(buf)) {
+		printk(BIOS_ERR, "%s: Not able to set date and time!\n", dev->chip_ops->name);
+	}
+}
+
+static void rtc_final(struct device *dev)
+{
+	uint8_t buf[7];
+
+	/* Read back current RTC date and time and print it to the console.
+	   Date and time are read in "one go", the buffer contains seconds (byte 0)
+	   through years (byte 6) after this read. */
+	if (i2c_dev_read_at(dev, buf, sizeof(buf), 0) != sizeof(buf)) {
+		printk(BIOS_ERR, "%s: Not able to read current date and time!\n",
+			dev->chip_ops->name);
+	} else {
+		printk(BIOS_INFO, "%s: Current date %02d.%02d.%02d %02d:%02d:%02d\n",
+				dev->chip_ops->name, bcd2bin(buf[5]), bcd2bin(buf[4]),
+				bcd2bin(buf[6]), bcd2bin(buf[2]), bcd2bin(buf[1]),
+				bcd2bin(buf[0]));
+	}
+	/* Make sure the EEPROM automatic refresh is enabled. */
+	if (rtc_eep_auto_refresh(dev, EEP_REFRESH_EN) != CB_SUCCESS) {
+		printk(BIOS_ERR, "%s: Not able to enable EEPROM auto refresh!\n",
+			dev->chip_ops->name);
+	}
+}
+
+static void rtc_init(struct device *dev)
+{
+	struct drivers_i2c_rv3028c7_config *config = dev->chip_info;
+	uint8_t reg, backup_reg, eep_update_needed = 0;
+
+	/* On every startup, the RTC synchronizes the internal EEPROM with RAM.
+	 * During this time no operation shall modify RAM registers. Ensure this
+	 * sync is finished before starting the initialization. */
+	if (rtc_eep_wait_ready(dev) != CB_SUCCESS) {
+		printk(BIOS_WARNING, "%s: Timeout on EEPROM sync after power on!\n",
+			dev->chip_ops->name);
+		return;
+	}
+	reg = backup_reg = (uint8_t)i2c_dev_readb_at(dev, EEP_BACKUP_REG);
+	/* Configure the switch-over setting according to devicetree. */
+	if (config->bckup_sw_mode) {
+		reg &= ~BSM_MASK;
+		reg |= config->bckup_sw_mode << BSM_BIT;
+	}
+	/* Configure the VBACKUP charging mode. */
+	if (config->cap_charge) {
+		reg &= ~TCR_MASK;
+		reg |= ((config->cap_charge - 1) << TCR_BIT);
+		reg |= TCE_BIT;
+	} else {
+		reg &= ~TCE_BIT;
+	}
+	/* According to the datasheet the Fast Edge Detection Enable (FEDE) bit
+	   should always be set. */
+	reg |= FEDE_BIT;
+	if (reg != backup_reg) {
+		/* Write new register value into shadow RAM and request an EEPROM update. */
+		i2c_dev_writeb_at(dev, EEP_BACKUP_REG, reg);
+		eep_update_needed = 1;
+	}
+	/* Make sure the hour register is in 24h format.*/
+	reg = (uint8_t)i2c_dev_readb_at(dev, CTRL2_REG);
+	if (reg & HOUR_12_24_BIT) {
+		reg &= ~HOUR_12_24_BIT;
+		i2c_dev_writeb_at(dev, CTRL2_REG, reg);
+	}
+	/* Check for a possible voltage drop event. */
+	reg = (uint8_t)i2c_dev_readb_at(dev, STATUS_REG);
+	if (reg & PORF_BIT) {
+		/* Voltage drop was detected, date and time needs to be set properly. */
+		rtc_set_time_date(dev);
+		/* Clear the PORF bit to mark that the event was handled. */
+		reg &= ~PORF_BIT;
+		i2c_dev_writeb_at(dev, STATUS_REG, reg);
+	}
+	/*
+	 * Finally, trigger the EEPROM update procedure if needed.
+	 * According to the datasheet, this update will consume ~63 ms.
+	 * In order to not block the boot process here waiting for this update being finished,
+	 * trigger the update now and check for readiness in the final hook.
+	 */
+	if (eep_update_needed && rtc_eep_start_update(dev) != CB_SUCCESS) {
+		printk(BIOS_ERR, "%s: Not able to trigger EEPROM update!\n",
+			dev->chip_ops->name);
+	}
+}
+
+static struct device_operations rv3028c7_ops = {
+	.read_resources		= noop_read_resources,
+	.set_resources		= noop_set_resources,
+	.init			= rtc_init,
+	.final			= rtc_final,
+};
+
+static void rtc_enable(struct device *dev)
+{
+	dev->ops = &rv3028c7_ops;
+}
+
+struct chip_operations drivers_i2c_rv3028c7_ops = {
+	CHIP_NAME("RV-3028-C7")
+	.enable_dev = rtc_enable
+};