[PATCH v5 2/4] mfd: Add driver for Embedded Controller found on Acer Iconia Tab A500

Dmitry Osipenko
2020-11-04T20:34:48Z

Acer Iconia Tab A500 is an Android tablet device, it has ENE KB930
Embedded Controller which provides battery-gauge, LED, GPIO and some
other functions. The EC uses firmware that is specifically customized
for Acer A500. This patch adds MFD driver for the Embedded Controller
which allows to power-off / reboot the A500 device, it also provides
a common register read/write API that will be used by the sub-devices.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/mfd/Kconfig | 12 +++
drivers/mfd/Makefile | 1 +
drivers/mfd/acer-ec-a500.c | 203 +++++++++++++++++++++++++++++++++++++
3 files changed, 216 insertions(+)
create mode 100644 drivers/mfd/acer-ec-a500.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 8b99a13669bf..527ba5054d80 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -2097,6 +2097,18 @@ config MFD_KHADAS_MCU
additional drivers must be enabled in order to use the functionality
of the device.

+config MFD_ACER_A500_EC
+ tristate "Embedded Controller driver for Acer Iconia Tab A500"
+ depends on I2C
+ depends on ARCH_TEGRA_2x_SOC || COMPILE_TEST
+ select MFD_CORE
+ select REGMAP
+ help
+ Support for Acer Iconia Tab A500 Embedded Controller.
+
+ The controller itself is ENE KB930, it is running firmware
+ customized for the specific needs of the Acer A500 hardware.
+
menu "Multimedia Capabilities Port drivers"
depends on ARCH_SA1100

diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 1780019d2474..7bfc57c8b363 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -263,6 +263,7 @@ obj-$(CONFIG_MFD_ROHM_BD71828) += rohm-bd71828.o
obj-$(CONFIG_MFD_ROHM_BD718XX) += rohm-bd718x7.o
obj-$(CONFIG_MFD_STMFX) += stmfx.o
obj-$(CONFIG_MFD_KHADAS_MCU) += khadas-mcu.o
+obj-$(CONFIG_MFD_ACER_A500_EC) += acer-ec-a500.o

obj-$(CONFIG_SGI_MFD_IOC3) += ioc3.o
obj-$(CONFIG_MFD_SIMPLE_MFD_I2C) += simple-mfd-i2c.o
diff --git a/drivers/mfd/acer-ec-a500.c b/drivers/mfd/acer-ec-a500.c
new file mode 100644
index 000000000000..2785a6d9bcc4
--- /dev/null
+++ b/drivers/mfd/acer-ec-a500.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * MFD driver for Acer Iconia Tab A500 Embedded Controller.
+ *
+ * Copyright 2020 GRATE-driver project.
+ *
+ * Based on downstream driver from Acer Inc.
+ */
+
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/reboot.h>
+
+#define A500_EC_I2C_ERR_TIMEOUT 500
+#define A500_EC_POWER_CMD_TIMEOUT 1000
+
+enum {
+ REG_CURRENT_NOW = 0x03,
+ REG_SHUTDOWN = 0x52,
+ REG_WARM_REBOOT = 0x54,
+ REG_COLD_REBOOT = 0x55,
+};
+
+static struct i2c_client *a500_ec_client_pm_off;
+
+static int a500_ec_read(void *context, const void *reg_buf, size_t reg_size,
+ void *val_buf, size_t val_sizel)
+{
+ struct i2c_client *client = context;
+ unsigned int reg, retries = 5;
+ u16 *ret_val = val_buf;
+ s32 ret = 0;
+
+ if (reg_size != 1 || val_sizel != 2)
+ return -EOPNOTSUPP;
+
+ reg = *(u8 *)reg_buf;
+
+ while (retries-- > 0) {
+ ret = i2c_smbus_read_word_data(client, reg);
+ if (ret >= 0)
+ break;
+
+ msleep(A500_EC_I2C_ERR_TIMEOUT);
+ }
+
+ if (ret < 0) {
+ dev_err(&client->dev, "read 0x%x failed: %d\n", reg, ret);
+ return ret;
+ }
+
+ *ret_val = ret;
+
+ if (reg == REG_CURRENT_NOW)
+ fsleep(10000);
+
+ return 0;
+}
+
+static int a500_ec_write(void *context, const void *data, size_t count)
+{
+ struct i2c_client *client = context;
+ unsigned int reg, val, retries = 5;
+ s32 ret = 0;
+
+ if (count != 3)
+ return -EOPNOTSUPP;
+
+ reg = *(u8 *)(data + 0);
+ val = *(u16 *)(data + 1);
+
+ while (retries-- > 0) {
+ ret = i2c_smbus_write_word_data(client, reg, val);
+ if (ret >= 0)
+ break;
+
+ msleep(A500_EC_I2C_ERR_TIMEOUT);
+ }
+
+ if (ret < 0) {
+ dev_err(&client->dev, "write 0x%x failed: %d\n", reg, ret);
+ return ret;
+ }
+
+ return 0;
+}
+
+static const struct regmap_config a500_ec_regmap_config = {
+ .name = "KB930",
+ .reg_bits = 8,
+ .val_bits = 16,
+ .max_register = 0xff,
+};
+
+static const struct regmap_bus a500_ec_regmap_bus = {
+ .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
+ .val_format_endian_default = REGMAP_ENDIAN_LITTLE,
+ .write = a500_ec_write,
+ .read = a500_ec_read,
+ .max_raw_read = 2,
+};
+
+static void a500_ec_poweroff(void)
+{
+ i2c_smbus_write_word_data(a500_ec_client_pm_off, REG_SHUTDOWN, 0);
+
+ mdelay(A500_EC_POWER_CMD_TIMEOUT);
+}
+
+static int a500_ec_restart_notify(struct notifier_block *this,
+ unsigned long reboot_mode, void *data)
+{
+ if (reboot_mode == REBOOT_WARM)
+ i2c_smbus_write_word_data(a500_ec_client_pm_off,
+ REG_WARM_REBOOT, 0);
+ else
+ i2c_smbus_write_word_data(a500_ec_client_pm_off,
+ REG_COLD_REBOOT, 1);
+
+ mdelay(A500_EC_POWER_CMD_TIMEOUT);
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block a500_ec_restart_handler = {
+ .notifier_call = a500_ec_restart_notify,
+ .priority = 200,
+};
+
+static const struct mfd_cell a500_ec_cells[] = {
+ { .name = "acer-a500-iconia-battery", },
+ { .name = "acer-a500-iconia-leds", },
+};
+
+static int a500_ec_probe(struct i2c_client *client)
+{
+ struct regmap *rmap;
+ int err;
+
+ rmap = devm_regmap_init(&client->dev, &a500_ec_regmap_bus,
+ client, &a500_ec_regmap_config);
+ if (IS_ERR(rmap))
+ return PTR_ERR(rmap);
+
+ /* register battery and LED sub-devices */
+ err = devm_mfd_add_devices(&client->dev, PLATFORM_DEVID_AUTO,
+ a500_ec_cells, ARRAY_SIZE(a500_ec_cells),
+ NULL, 0, NULL);
+ if (err) {
+ dev_err(&client->dev, "failed to add sub-devices: %d\n", err);
+ return err;
+ }
+
+ /* set up power management functions */
+ if (of_device_is_system_power_controller(client->dev.of_node)) {
+ a500_ec_client_pm_off = client;
+
+ err = register_restart_handler(&a500_ec_restart_handler);
+ if (err)
+ return err;
+
+ if (!pm_power_off)
+ pm_power_off = a500_ec_poweroff;
+ }
+
+ return 0;
+}
+
+static int a500_ec_remove(struct i2c_client *client)
+{
+ if (of_device_is_system_power_controller(client->dev.of_node)) {
+ if (pm_power_off == a500_ec_poweroff)
+ pm_power_off = NULL;
+
+ unregister_restart_handler(&a500_ec_restart_handler);
+ }
+
+ return 0;
+}
+
+static const struct of_device_id a500_ec_match[] = {
+ { .compatible = "acer,a500-iconia-ec" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, a500_ec_match);
+
+static struct i2c_driver a500_ec_driver = {
+ .driver = {
+ .name = "acer-a500-embedded-controller",
+ .of_match_table = a500_ec_match,
+ },
+ .probe_new = a500_ec_probe,
+ .remove = a500_ec_remove,
+};
+module_i2c_driver(a500_ec_driver);
+
+MODULE_DESCRIPTION("Acer Iconia Tab A500 Embedded Controller driver");
+MODULE_AUTHOR("Dmitry Osipenko <digetx@gmail.com>");
+MODULE_LICENSE("GPL");
--
2.27.0