[PATCH v1 1/6] mfd: Add driver for Embedded Controller found on Acer Iconia Tab A500

[Dmitry Osipenko <digetx@gmail.com>]

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              |  10 ++
 drivers/mfd/Makefile             |   1 +
 drivers/mfd/acer-ec-a500.c       | 196 +++++++++++++++++++++++++++++++
 include/linux/mfd/acer-ec-a500.h |  80 +++++++++++++
 4 files changed, 287 insertions(+)
 create mode 100644 drivers/mfd/acer-ec-a500.c
 create mode 100644 include/linux/mfd/acer-ec-a500.h

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 33df0837ab41..9e5cf88a52d8 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -2062,6 +2062,16 @@ 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_TEGRA && ARCH_TEGRA_2x_SOC) || COMPILE_TEST
+	select MFD_CORE
+	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 a60e5f835283..6e3a6162ad94 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -262,5 +262,6 @@ 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
diff --git a/drivers/mfd/acer-ec-a500.c b/drivers/mfd/acer-ec-a500.c
new file mode 100644
index 000000000000..f75bb60ab408
--- /dev/null
+++ b/drivers/mfd/acer-ec-a500.c
@@ -0,0 +1,196 @@
+// 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/irqflags.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/reboot.h>
+
+#include <linux/mfd/acer-ec-a500.h>
+#include <linux/mfd/core.h>
+
+#define A500_EC_I2C_ERR_TIMEOUT		500
+
+/*				cmd	delay ms */
+A500_EC_COMMAND(SHUTDOWN,	0x52,	1000);
+A500_EC_COMMAND(WARM_REBOOT,	0x54,	1000);
+A500_EC_COMMAND(COLD_REBOOT,	0x55,	1000);
+
+static struct a500_ec *a500_ec_scratch;
+
+static void a500_ec_delay(unsigned int delay_ms)
+{
+	/* interrupts could be disabled on shutdown or reboot */
+	if (irqs_disabled())
+		mdelay(delay_ms);
+	else
+		msleep(delay_ms);
+}
+
+int a500_ec_read_locked(struct a500_ec *ec_chip,
+			const struct a500_ec_cmd *cmd_desc)
+{
+	struct i2c_client *client = ec_chip->client;
+	unsigned int retries = 5;
+	s32 ret = 0;
+
+	while (retries-- > 0) {
+		ret = i2c_smbus_read_word_data(client, cmd_desc->cmd);
+		if (ret >= 0)
+			break;
+
+		a500_ec_delay(A500_EC_I2C_ERR_TIMEOUT);
+	}
+
+	if (ret < 0) {
+		dev_err(&client->dev, "i2c read command 0x%x failed: %d\n",
+			cmd_desc->cmd, ret);
+		return ret;
+	}
+
+	a500_ec_delay(cmd_desc->post_delay);
+
+	return le16_to_cpu(ret);
+}
+EXPORT_SYMBOL_GPL(a500_ec_read_locked);
+
+int a500_ec_write_locked(struct a500_ec *ec_chip,
+			 const struct a500_ec_cmd *cmd_desc, u16 value)
+{
+	struct i2c_client *client = ec_chip->client;
+	unsigned int retries = 5;
+	s32 ret = 0;
+
+	while (retries-- > 0) {
+		ret = i2c_smbus_write_word_data(client, cmd_desc->cmd,
+						le16_to_cpu(value));
+		if (ret >= 0)
+			break;
+
+		a500_ec_delay(A500_EC_I2C_ERR_TIMEOUT);
+	}
+
+	if (ret < 0) {
+		dev_err(&client->dev, "i2c write command 0x%x failed: %d\n",
+			cmd_desc->cmd, ret);
+		return ret;
+	}
+
+	a500_ec_delay(cmd_desc->post_delay);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(a500_ec_write_locked);
+
+static void a500_ec_poweroff(void)
+{
+	struct a500_ec *ec_chip = a500_ec_scratch;
+
+	a500_ec_write_locked(ec_chip, SHUTDOWN, 0);
+}
+
+static int a500_ec_restart_notify(struct notifier_block *this,
+				  unsigned long reboot_mode, void *data)
+{
+	struct a500_ec *ec_chip = a500_ec_scratch;
+
+	if (reboot_mode == REBOOT_WARM)
+		a500_ec_write_locked(ec_chip, WARM_REBOOT, 0);
+	else
+		a500_ec_write_locked(ec_chip, COLD_REBOOT, 1);
+
+	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,
+			 const struct i2c_device_id *id)
+{
+	struct a500_ec *ec_chip;
+	int err;
+
+	ec_chip = devm_kzalloc(&client->dev, sizeof(*ec_chip), GFP_KERNEL);
+	if (!ec_chip)
+		return -ENOMEM;
+
+	ec_chip->client = client;
+	mutex_init(&ec_chip->lock);
+
+	i2c_set_clientdata(client, ec_chip);
+
+	/* 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_scratch = ec_chip;
+
+		err = register_restart_handler(&a500_ec_restart_handler);
+		if (err) {
+			dev_err(&client->dev,
+				"unable to register restart handler: %d\n",
+				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 = 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 v2");
diff --git a/include/linux/mfd/acer-ec-a500.h b/include/linux/mfd/acer-ec-a500.h
new file mode 100644
index 000000000000..08bc681e6525
--- /dev/null
+++ b/include/linux/mfd/acer-ec-a500.h
@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * API for Embedded Controller of Acer Iconia Tab A500.
+ *
+ * Copyright 2020 GRATE-driver project.
+ */
+
+#ifndef __LINUX_MFD_ACER_A500_EC_H
+#define __LINUX_MFD_ACER_A500_EC_H
+
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+struct a500_ec_cmd {
+	unsigned int cmd;
+	unsigned int post_delay;
+};
+
+#define A500_EC_COMMAND(NAME, CMD, DELAY_MS)				\
+static const struct a500_ec_cmd A500_EC_##NAME = {			\
+	.cmd = CMD,							\
+	.post_delay = DELAY_MS,						\
+};									\
+static const __maybe_unused struct a500_ec_cmd *NAME = &A500_EC_##NAME
+
+struct a500_ec {
+	struct i2c_client *client;
+
+	/*
+	 * Some EC commands shall be executed sequentially and some commands
+	 * shall not be executed instantly after the other commands. Hence the
+	 * locking is needed in order to protect from conflicting accesses to
+	 * the EC.
+	 */
+	struct mutex lock;
+};
+
+int a500_ec_read_locked(struct a500_ec *ec_chip,
+			const struct a500_ec_cmd *cmd_desc);
+
+int a500_ec_write_locked(struct a500_ec *ec_chip,
+			 const struct a500_ec_cmd *cmd_desc, u16 value);
+
+static inline void a500_ec_lock(struct a500_ec *ec_chip)
+{
+	mutex_lock(&ec_chip->lock);
+}
+
+static inline void a500_ec_unlock(struct a500_ec *ec_chip)
+{
+	mutex_unlock(&ec_chip->lock);
+}
+
+static inline int a500_ec_read(struct a500_ec *ec_chip,
+			       const struct a500_ec_cmd *cmd_desc)
+{
+	s32 ret;
+
+	a500_ec_lock(ec_chip);
+	ret = a500_ec_read_locked(ec_chip, cmd_desc);
+	a500_ec_unlock(ec_chip);
+
+	return ret;
+}
+
+static inline int a500_ec_write(struct a500_ec *ec_chip,
+				const struct a500_ec_cmd *cmd_desc,
+				u16 value)
+{
+	s32 ret;
+
+	a500_ec_lock(ec_chip);
+	ret = a500_ec_write_locked(ec_chip, cmd_desc, value);
+	a500_ec_unlock(ec_chip);
+
+	return ret;
+}
+
+#endif /* __LINUX_MFD_ACER_A500_EC_H */
-- 
2.27.0