Platform: OLPC: Add XO-1.75 EC driver

It's based off the driver from the OLPC kernel sources. Somewhat
modernized and cleaned up, for better or worse.

Modified to plug into the olpc-ec driver infrastructure (so that battery
interface and debugfs could be reused) and the SPI slave framework.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

5 files changed, 771 insertions, 2 deletions

diff --git a/drivers/platform/Kconfig b/drivers/platform/Kconfig
index d4c2e424a700..4313d73d3618 100644
--- a/drivers/platform/Kconfig
+++ b/drivers/platform/Kconfig
@@ -10,3 +10,5 @@ source "drivers/platform/goldfish/Kconfig"
 source "drivers/platform/chrome/Kconfig"
 
 source "drivers/platform/mellanox/Kconfig"
+
+source "drivers/platform/olpc/Kconfig"
diff --git a/drivers/platform/Makefile b/drivers/platform/Makefile
index 4b2ce58bcd9c..6fda58c021ca 100644
--- a/drivers/platform/Makefile
+++ b/drivers/platform/Makefile
@@ -6,6 +6,6 @@
 obj-$(CONFIG_X86)		+= x86/
 obj-$(CONFIG_MELLANOX_PLATFORM)	+= mellanox/
 obj-$(CONFIG_MIPS)		+= mips/
-obj-$(CONFIG_OLPC)		+= olpc/
+obj-$(CONFIG_OLPC_EC)		+= olpc/
 obj-$(CONFIG_GOLDFISH)		+= goldfish/
 obj-$(CONFIG_CHROME_PLATFORMS)	+= chrome/
diff --git a/drivers/platform/olpc/Kconfig b/drivers/platform/olpc/Kconfig
new file mode 100644
index 000000000000..559f843199d7
--- /dev/null
+++ b/drivers/platform/olpc/Kconfig
@@ -0,0 +1,14 @@
+config OLPC_EC
+	bool
+
+config OLPC_XO175_EC
+	tristate "OLPC XO 1.75 Embedded Controller"
+	depends on ARCH_MMP || COMPILE_TEST
+	select SPI_SLAVE
+	select OLPC_EC
+	help
+	  Include support for the OLPC XO Embedded Controller (EC). The EC
+	  provides various platform services, including support for the power,
+	  button, restart, shutdown and battery charging status.
+
+	  Unless you have an OLPC XO laptop, you will want to say N.
diff --git a/drivers/platform/olpc/Makefile b/drivers/platform/olpc/Makefile
index dc8b26bc7209..01fe6ba01665 100644
--- a/drivers/platform/olpc/Makefile
+++ b/drivers/platform/olpc/Makefile
@@ -1,4 +1,5 @@
 #
 # OLPC XO platform-specific drivers
 #
-obj-$(CONFIG_OLPC)		+= olpc-ec.o
+obj-$(CONFIG_OLPC_EC)		+= olpc-ec.o
+obj-$(CONFIG_OLPC_XO175_EC)	+= olpc-xo175-ec.o
diff --git a/drivers/platform/olpc/olpc-xo175-ec.c b/drivers/platform/olpc/olpc-xo175-ec.c
new file mode 100644
index 000000000000..344d14f3da54
--- /dev/null
+++ b/drivers/platform/olpc/olpc-xo175-ec.c
@@ -0,0 +1,752 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for the OLPC XO-1.75 Embedded Controller.
+ *
+ * The EC protocol is documented at:
+ * http://wiki.laptop.org/go/XO_1.75_HOST_to_EC_Protocol
+ *
+ * Copyright (C) 2010 One Laptop per Child Foundation.
+ * Copyright (C) 2018 Lubomir Rintel <lkundrak@v3.sk>
+ */
+
+#include <linux/completion.h>
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/input.h>
+#include <linux/kfifo.h>
+#include <linux/module.h>
+#include <linux/olpc-ec.h>
+#include <linux/platform_device.h>
+#include <linux/power_supply.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/spi/spi.h>
+
+struct ec_cmd_t {
+	u8 cmd;
+	u8 bytes_returned;
+};
+
+enum ec_chan_t {
+	CHAN_NONE = 0,
+	CHAN_SWITCH,
+	CHAN_CMD_RESP,
+	CHAN_KEYBOARD,
+	CHAN_TOUCHPAD,
+	CHAN_EVENT,
+	CHAN_DEBUG,
+	CHAN_CMD_ERROR,
+};
+
+/*
+ * EC events
+ */
+#define EVENT_AC_CHANGE			1  /* AC plugged/unplugged */
+#define EVENT_BATTERY_STATUS		2  /* Battery low/full/error/gone */
+#define EVENT_BATTERY_CRITICAL		3  /* Battery critical voltage */
+#define EVENT_BATTERY_SOC_CHANGE	4  /* 1% SOC Change */
+#define EVENT_BATTERY_ERROR		5  /* Abnormal error, query for cause */
+#define EVENT_POWER_PRESSED		6  /* Power button was pressed */
+#define EVENT_POWER_PRESS_WAKE		7  /* Woken up with a power button */
+#define EVENT_TIMED_HOST_WAKE		8  /* Host wake timer */
+#define EVENT_OLS_HIGH_LIMIT		9  /* OLS crossed dark threshold */
+#define EVENT_OLS_LOW_LIMIT		10 /* OLS crossed light threshold */
+
+/*
+ * EC commands
+ * (from http://dev.laptop.org/git/users/rsmith/ec-1.75/tree/ec_cmd.h)
+ */
+#define CMD_GET_API_VERSION		0x08 /* out: u8 */
+#define CMD_READ_VOLTAGE		0x10 /* out: u16, *9.76/32, mV */
+#define CMD_READ_CURRENT		0x11 /* out: s16, *15.625/120, mA */
+#define CMD_READ_ACR			0x12 /* out: s16, *6250/15, uAh */
+#define CMD_READ_BATT_TEMPERATURE	0x13 /* out: u16, *100/256, deg C */
+#define CMD_READ_AMBIENT_TEMPERATURE	0x14 /* unimplemented, no hardware */
+#define CMD_READ_BATTERY_STATUS		0x15 /* out: u8, bitmask */
+#define CMD_READ_SOC			0x16 /* out: u8, percentage */
+#define CMD_READ_GAUGE_ID		0x17 /* out: u8 * 8 */
+#define CMD_READ_GAUGE_DATA		0x18 /* in: u8 addr, out: u8 data */
+#define CMD_READ_BOARD_ID		0x19 /* out: u16 (platform id) */
+#define CMD_READ_BATT_ERR_CODE		0x1f /* out: u8, error bitmask */
+#define CMD_SET_DCON_POWER		0x26 /* in: u8 */
+#define CMD_RESET_EC			0x28 /* none */
+#define CMD_READ_BATTERY_TYPE		0x2c /* out: u8 */
+#define CMD_SET_AUTOWAK			0x33 /* out: u8 */
+#define CMD_SET_EC_WAKEUP_TIMER		0x36 /* in: u32, out: ? */
+#define CMD_READ_EXT_SCI_MASK		0x37 /* ? */
+#define CMD_WRITE_EXT_SCI_MASK		0x38 /* ? */
+#define CMD_CLEAR_EC_WAKEUP_TIMER	0x39 /* none */
+#define CMD_ENABLE_RUNIN_DISCHARGE	0x3B /* none */
+#define CMD_DISABLE_RUNIN_DISCHARGE	0x3C /* none */
+#define CMD_READ_MPPT_ACTIVE		0x3d /* out: u8 */
+#define CMD_READ_MPPT_LIMIT		0x3e /* out: u8 */
+#define CMD_SET_MPPT_LIMIT		0x3f /* in: u8 */
+#define CMD_DISABLE_MPPT		0x40 /* none */
+#define CMD_ENABLE_MPPT			0x41 /* none */
+#define CMD_READ_VIN			0x42 /* out: u16 */
+#define CMD_EXT_SCI_QUERY		0x43 /* ? */
+#define RSP_KEYBOARD_DATA		0x48 /* ? */
+#define RSP_TOUCHPAD_DATA		0x49 /* ? */
+#define CMD_GET_FW_VERSION		0x4a /* out: u8 * 16 */
+#define CMD_POWER_CYCLE			0x4b /* none */
+#define CMD_POWER_OFF			0x4c /* none */
+#define CMD_RESET_EC_SOFT		0x4d /* none */
+#define CMD_READ_GAUGE_U16		0x4e /* ? */
+#define CMD_ENABLE_MOUSE		0x4f /* ? */
+#define CMD_ECHO			0x52 /* in: u8 * 5, out: u8 * 5 */
+#define CMD_GET_FW_DATE			0x53 /* out: u8 * 16 */
+#define CMD_GET_FW_USER			0x54 /* out: u8 * 16 */
+#define CMD_TURN_OFF_POWER		0x55 /* none (same as 0x4c) */
+#define CMD_READ_OLS			0x56 /* out: u16 */
+#define CMD_OLS_SMT_LEDON		0x57 /* none */
+#define CMD_OLS_SMT_LEDOFF		0x58 /* none */
+#define CMD_START_OLS_ASSY		0x59 /* none */
+#define CMD_STOP_OLS_ASSY		0x5a /* none */
+#define CMD_OLS_SMTTEST_STOP		0x5b /* none */
+#define CMD_READ_VIN_SCALED		0x5c /* out: u16 */
+#define CMD_READ_BAT_MIN_W		0x5d /* out: u16 */
+#define CMD_READ_BAR_MAX_W		0x5e /* out: u16 */
+#define CMD_RESET_BAT_MINMAX_W		0x5f /* none */
+#define CMD_READ_LOCATION		0x60 /* in: u16 addr, out: u8 data */
+#define CMD_WRITE_LOCATION		0x61 /* in: u16 addr, u8 data */
+#define CMD_KEYBOARD_CMD		0x62 /* in: u8, out: ? */
+#define CMD_TOUCHPAD_CMD		0x63 /* in: u8, out: ? */
+#define CMD_GET_FW_HASH			0x64 /* out: u8 * 16 */
+#define CMD_SUSPEND_HINT		0x65 /* in: u8 */
+#define CMD_ENABLE_WAKE_TIMER		0x66 /* in: u8 */
+#define CMD_SET_WAKE_TIMER		0x67 /* in: 32 */
+#define CMD_ENABLE_WAKE_AUTORESET	0x68 /* in: u8 */
+#define CMD_OLS_SET_LIMITS		0x69 /* in: u16, u16 */
+#define CMD_OLS_GET_LIMITS		0x6a /* out: u16, u16 */
+#define CMD_OLS_SET_CEILING		0x6b /* in: u16 */
+#define CMD_OLS_GET_CEILING		0x6c /* out: u16 */
+
+/*
+ * Accepted EC commands, and how many bytes they return. There are plenty
+ * of EC commands that are no longer implemented, or are implemented only on
+ * certain older boards.
+ */
+static const struct ec_cmd_t olpc_xo175_ec_cmds[] = {
+	{ CMD_GET_API_VERSION, 1 },
+	{ CMD_READ_VOLTAGE, 2 },
+	{ CMD_READ_CURRENT, 2 },
+	{ CMD_READ_ACR, 2 },
+	{ CMD_READ_BATT_TEMPERATURE, 2 },
+	{ CMD_READ_BATTERY_STATUS, 1 },
+	{ CMD_READ_SOC, 1 },
+	{ CMD_READ_GAUGE_ID, 8 },
+	{ CMD_READ_GAUGE_DATA, 1 },
+	{ CMD_READ_BOARD_ID, 2 },
+	{ CMD_READ_BATT_ERR_CODE, 1 },
+	{ CMD_SET_DCON_POWER, 0 },
+	{ CMD_RESET_EC, 0 },
+	{ CMD_READ_BATTERY_TYPE, 1 },
+	{ CMD_ENABLE_RUNIN_DISCHARGE, 0 },
+	{ CMD_DISABLE_RUNIN_DISCHARGE, 0 },
+	{ CMD_READ_MPPT_ACTIVE, 1 },
+	{ CMD_READ_MPPT_LIMIT, 1 },
+	{ CMD_SET_MPPT_LIMIT, 0 },
+	{ CMD_DISABLE_MPPT, 0 },
+	{ CMD_ENABLE_MPPT, 0 },
+	{ CMD_READ_VIN, 2 },
+	{ CMD_GET_FW_VERSION, 16 },
+	{ CMD_POWER_CYCLE, 0 },
+	{ CMD_POWER_OFF, 0 },
+	{ CMD_RESET_EC_SOFT, 0 },
+	{ CMD_ECHO, 5 },
+	{ CMD_GET_FW_DATE, 16 },
+	{ CMD_GET_FW_USER, 16 },
+	{ CMD_TURN_OFF_POWER, 0 },
+	{ CMD_READ_OLS, 2 },
+	{ CMD_OLS_SMT_LEDON, 0 },
+	{ CMD_OLS_SMT_LEDOFF, 0 },
+	{ CMD_START_OLS_ASSY, 0 },
+	{ CMD_STOP_OLS_ASSY, 0 },
+	{ CMD_OLS_SMTTEST_STOP, 0 },
+	{ CMD_READ_VIN_SCALED, 2 },
+	{ CMD_READ_BAT_MIN_W, 2 },
+	{ CMD_READ_BAR_MAX_W, 2 },
+	{ CMD_RESET_BAT_MINMAX_W, 0 },
+	{ CMD_READ_LOCATION, 1 },
+	{ CMD_WRITE_LOCATION, 0 },
+	{ CMD_GET_FW_HASH, 16 },
+	{ CMD_SUSPEND_HINT, 0 },
+	{ CMD_ENABLE_WAKE_TIMER, 0 },
+	{ CMD_SET_WAKE_TIMER, 0 },
+	{ CMD_ENABLE_WAKE_AUTORESET, 0 },
+	{ CMD_OLS_SET_LIMITS, 0 },
+	{ CMD_OLS_GET_LIMITS, 4 },
+	{ CMD_OLS_SET_CEILING, 0 },
+	{ CMD_OLS_GET_CEILING, 2 },
+	{ CMD_READ_EXT_SCI_MASK, 2 },
+	{ CMD_WRITE_EXT_SCI_MASK, 0 },
+
+	{ }
+};
+
+#define EC_MAX_CMD_DATA_LEN	5
+#define EC_MAX_RESP_LEN		16
+
+#define LOG_BUF_SIZE		128
+
+#define PM_WAKEUP_TIME		1000
+
+#define EC_ALL_EVENTS		GENMASK(15, 0)
+
+enum ec_state_t {
+	CMD_STATE_IDLE = 0,
+	CMD_STATE_WAITING_FOR_SWITCH,
+	CMD_STATE_CMD_IN_TX_FIFO,
+	CMD_STATE_CMD_SENT,
+	CMD_STATE_RESP_RECEIVED,
+	CMD_STATE_ERROR_RECEIVED,
+};
+
+struct olpc_xo175_ec_cmd {
+	u8 command;
+	u8 nr_args;
+	u8 data_len;
+	u8 args[EC_MAX_CMD_DATA_LEN];
+};
+
+struct olpc_xo175_ec_resp {
+	u8 channel;
+	u8 byte;
+};
+
+struct olpc_xo175_ec {
+	bool suspended;
+
+	/* SPI related stuff. */
+	struct spi_device *spi;
+	struct spi_transfer xfer;
+	struct spi_message msg;
+	union {
+		struct olpc_xo175_ec_cmd cmd;
+		struct olpc_xo175_ec_resp resp;
+	} tx_buf, rx_buf;
+
+	/* GPIO for the CMD signals. */
+	struct gpio_desc *gpio_cmd;
+
+	/* Command handling related state. */
+	spinlock_t cmd_state_lock;
+	int cmd_state;
+	bool cmd_running;
+	struct completion cmd_done;
+	struct olpc_xo175_ec_cmd cmd;
+	u8 resp_data[EC_MAX_RESP_LEN];
+	int expected_resp_len;
+	int resp_len;
+
+	/* Power button. */
+	struct input_dev *pwrbtn;
+
+	/* Debug handling. */
+	char logbuf[LOG_BUF_SIZE];
+	int logbuf_len;
+};
+
+static struct platform_device *olpc_ec;
+
+static int olpc_xo175_ec_resp_len(u8 cmd)
+{
+	const struct ec_cmd_t *p;
+
+	for (p = olpc_xo175_ec_cmds; p->cmd; p++) {
+		if (p->cmd == cmd)
+			return p->bytes_returned;
+	}
+
+	return -EINVAL;
+}
+
+static void olpc_xo175_ec_flush_logbuf(struct olpc_xo175_ec *priv)
+{
+	dev_dbg(&priv->spi->dev, "got debug string [%*pE]\n",
+				priv->logbuf_len, priv->logbuf);
+	priv->logbuf_len = 0;
+}
+
+static void olpc_xo175_ec_complete(void *arg);
+
+static void olpc_xo175_ec_send_command(struct olpc_xo175_ec *priv, void *cmd,
+								size_t cmdlen)
+{
+	int ret;
+
+	memcpy(&priv->tx_buf, cmd, cmdlen);
+	priv->xfer.len = cmdlen;
+
+	spi_message_init_with_transfers(&priv->msg, &priv->xfer, 1);
+
+	priv->msg.complete = olpc_xo175_ec_complete;
+	priv->msg.context = priv;
+
+	ret = spi_async(priv->spi, &priv->msg);
+	if (ret)
+		dev_err(&priv->spi->dev, "spi_async() failed %d\n", ret);
+}
+
+static void olpc_xo175_ec_read_packet(struct olpc_xo175_ec *priv)
+{
+	u8 nonce[] = {0xA5, 0x5A};
+
+	olpc_xo175_ec_send_command(priv, nonce, sizeof(nonce));
+}
+
+static void olpc_xo175_ec_complete(void *arg)
+{
+	struct olpc_xo175_ec *priv = arg;
+	struct device *dev = &priv->spi->dev;
+	struct power_supply *psy;
+	unsigned long flags;
+	u8 channel;
+	u8 byte;
+	int ret;
+
+	ret = priv->msg.status;
+	if (ret) {
+		dev_err(dev, "SPI transfer failed: %d\n", ret);
+
+		spin_lock_irqsave(&priv->cmd_state_lock, flags);
+		if (priv->cmd_running) {
+			priv->resp_len = 0;
+			priv->cmd_state = CMD_STATE_ERROR_RECEIVED;
+			complete(&priv->cmd_done);
+		}
+		spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+
+		if (ret != -EINTR)
+			olpc_xo175_ec_read_packet(priv);
+
+		return;
+	}
+
+	channel = priv->rx_buf.resp.channel;
+	byte = priv->rx_buf.resp.byte;
+
+	switch (channel) {
+	case CHAN_NONE:
+		spin_lock_irqsave(&priv->cmd_state_lock, flags);
+
+		if (!priv->cmd_running) {
+			/* We can safely ignore these */
+			dev_err(dev, "spurious FIFO read packet\n");
+			spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+			return;
+		}
+
+		priv->cmd_state = CMD_STATE_CMD_SENT;
+		if (!priv->expected_resp_len)
+			complete(&priv->cmd_done);
+		olpc_xo175_ec_read_packet(priv);
+
+		spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+		return;
+
+	case CHAN_SWITCH:
+		spin_lock_irqsave(&priv->cmd_state_lock, flags);
+
+		if (!priv->cmd_running) {
+			/* Just go with the flow */
+			dev_err(dev, "spurious SWITCH packet\n");
+			memset(&priv->cmd, 0, sizeof(priv->cmd));
+			priv->cmd.command = CMD_ECHO;
+		}
+
+		priv->cmd_state = CMD_STATE_CMD_IN_TX_FIFO;
+
+		/* Throw command into TxFIFO */
+		gpiod_set_value_cansleep(priv->gpio_cmd, 0);
+		olpc_xo175_ec_send_command(priv, &priv->cmd, sizeof(priv->cmd));
+
+		spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+		return;
+
+	case CHAN_CMD_RESP:
+		spin_lock_irqsave(&priv->cmd_state_lock, flags);
+
+		if (!priv->cmd_running) {
+			dev_err(dev, "spurious response packet\n");
+		} else if (priv->resp_len >= priv->expected_resp_len) {
+			dev_err(dev, "too many response packets\n");
+		} else {
+			priv->resp_data[priv->resp_len++] = byte;
+			if (priv->resp_len == priv->expected_resp_len) {
+				priv->cmd_state = CMD_STATE_RESP_RECEIVED;
+				complete(&priv->cmd_done);
+			}
+		}
+
+		spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+		break;
+
+	case CHAN_CMD_ERROR:
+		spin_lock_irqsave(&priv->cmd_state_lock, flags);
+
+		if (!priv->cmd_running) {
+			dev_err(dev, "spurious cmd error packet\n");
+		} else {
+			priv->resp_data[0] = byte;
+			priv->resp_len = 1;
+			priv->cmd_state = CMD_STATE_ERROR_RECEIVED;
+			complete(&priv->cmd_done);
+		}
+		spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+		break;
+
+	case CHAN_KEYBOARD:
+		dev_warn(dev, "keyboard is not supported\n");
+		break;
+
+	case CHAN_TOUCHPAD:
+		dev_warn(dev, "touchpad is not supported\n");
+		break;
+
+	case CHAN_EVENT:
+		dev_dbg(dev, "got event %.2x\n", byte);
+		switch (byte) {
+		case EVENT_AC_CHANGE:
+			psy = power_supply_get_by_name("olpc-ac");
+			if (psy) {
+				power_supply_changed(psy);
+				power_supply_put(psy);
+			}
+			break;
+		case EVENT_BATTERY_STATUS:
+		case EVENT_BATTERY_CRITICAL:
+		case EVENT_BATTERY_SOC_CHANGE:
+		case EVENT_BATTERY_ERROR:
+			psy = power_supply_get_by_name("olpc-battery");
+			if (psy) {
+				power_supply_changed(psy);
+				power_supply_put(psy);
+			}
+			break;
+		case EVENT_POWER_PRESSED:
+			input_report_key(priv->pwrbtn, KEY_POWER, 1);
+			input_sync(priv->pwrbtn);
+			input_report_key(priv->pwrbtn, KEY_POWER, 0);
+			input_sync(priv->pwrbtn);
+			/* fall through */
+		case EVENT_POWER_PRESS_WAKE:
+		case EVENT_TIMED_HOST_WAKE:
+			pm_wakeup_event(priv->pwrbtn->dev.parent,
+						PM_WAKEUP_TIME);
+			break;
+		default:
+			dev_dbg(dev, "ignored unknown event %.2x\n", byte);
+			break;
+		}
+		break;
+
+	case CHAN_DEBUG:
+		if (byte == '\n') {
+			olpc_xo175_ec_flush_logbuf(priv);
+		} else if (isprint(byte)) {
+			priv->logbuf[priv->logbuf_len++] = byte;
+			if (priv->logbuf_len == LOG_BUF_SIZE)
+				olpc_xo175_ec_flush_logbuf(priv);
+		}
+		break;
+
+	default:
+		dev_warn(dev, "unknown channel: %d, %.2x\n", channel, byte);
+		break;
+	}
+
+	/* Most non-command packets get the TxFIFO refilled and an ACK. */
+	olpc_xo175_ec_read_packet(priv);
+}
+
+/*
+ * This function is protected with a mutex. We can safely assume that
+ * there will be only one instance of this function running at a time.
+ * One of the ways in which we enforce this is by waiting until we get
+ * all response bytes back from the EC, rather than just the number that
+ * the caller requests (otherwise, we might start a new command while an
+ * old command's response bytes are still incoming).
+ */
+static int olpc_xo175_ec_cmd(u8 cmd, u8 *inbuf, size_t inlen, u8 *resp,
+					size_t resp_len, void *ec_cb_arg)
+{
+	struct olpc_xo175_ec *priv = ec_cb_arg;
+	struct device *dev = &priv->spi->dev;
+	unsigned long flags;
+	size_t nr_bytes;
+	int ret = 0;
+
+	dev_dbg(dev, "CMD %x, %zd bytes expected\n", cmd, resp_len);
+
+	if (inlen > 5) {
+		dev_err(dev, "command len %zd too big!\n", resp_len);
+		return -EOVERFLOW;
+	}
+
+	/* Suspending in the middle of an EC command hoses things badly! */
+	if (WARN_ON(priv->suspended))
+		return -EBUSY;
+
+	/* Ensure a valid command and return bytes */
+	ret = olpc_xo175_ec_resp_len(cmd);
+	if (ret < 0) {
+		dev_err_ratelimited(dev, "unknown command 0x%x\n", cmd);
+
+		/*
+		 * Assume the best in our callers, and allow unknown commands
+		 * through. I'm not the charitable type, but it was beaten
+		 * into me. Just maintain a minimum standard of sanity.
+		 */
+		if (resp_len > sizeof(priv->resp_data)) {
+			dev_err(dev, "response too big: %zd!\n", resp_len);
+			return -EOVERFLOW;
+		}
+		nr_bytes = resp_len;
+	} else {
+		nr_bytes = (size_t)ret;
+	}
+	resp_len = min(resp_len, nr_bytes);
+
+	spin_lock_irqsave(&priv->cmd_state_lock, flags);
+
+	/* Initialize the state machine */
+	init_completion(&priv->cmd_done);
+	priv->cmd_running = true;
+	priv->cmd_state = CMD_STATE_WAITING_FOR_SWITCH;
+	memset(&priv->cmd, 0, sizeof(priv->cmd));
+	priv->cmd.command = cmd;
+	priv->cmd.nr_args = inlen;
+	priv->cmd.data_len = 0;
+	memcpy(priv->cmd.args, inbuf, inlen);
+	priv->expected_resp_len = nr_bytes;
+	priv->resp_len = 0;
+
+	/* Tickle the cmd gpio to get things started */
+	gpiod_set_value_cansleep(priv->gpio_cmd, 1);
+
+	spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+
+	/* The irq handler should do the rest */
+	if (!wait_for_completion_timeout(&priv->cmd_done,
+			msecs_to_jiffies(4000))) {
+		dev_err(dev, "EC cmd error: timeout in STATE %d\n",
+				priv->cmd_state);
+		gpiod_set_value_cansleep(priv->gpio_cmd, 0);
+		spi_slave_abort(priv->spi);
+		olpc_xo175_ec_read_packet(priv);
+		return -ETIMEDOUT;
+	}
+
+	spin_lock_irqsave(&priv->cmd_state_lock, flags);
+
+	/* Deal with the results. */
+	if (priv->cmd_state == CMD_STATE_ERROR_RECEIVED) {
+		/* EC-provided error is in the single response byte */
+		dev_err(dev, "command 0x%x returned error 0x%x\n",
+						cmd, priv->resp_data[0]);
+		ret = -EREMOTEIO;
+	} else if (priv->resp_len != nr_bytes) {
+		dev_err(dev, "command 0x%x returned %d bytes, expected %zd bytes\n",
+						cmd, priv->resp_len, nr_bytes);
+		ret = -EREMOTEIO;
+	} else {
+		/*
+		 * We may have 8 bytes in priv->resp, but we only care about
+		 * what we've been asked for. If the caller asked for only 2
+		 * bytes, give them that. We've guaranteed that
+		 * resp_len <= priv->resp_len and priv->resp_len == nr_bytes.
+		 */
+		memcpy(resp, priv->resp_data, resp_len);
+	}
+
+	/* This should already be low, but just in case. */
+	gpiod_set_value_cansleep(priv->gpio_cmd, 0);
+	priv->cmd_running = false;
+
+	spin_unlock_irqrestore(&priv->cmd_state_lock, flags);
+
+	return ret;
+}
+
+static int olpc_xo175_ec_set_event_mask(unsigned int mask)
+{
+	u8 args[2];
+
+	args[0] = mask >> 0;
+	args[1] = mask >> 8;
+	return olpc_ec_cmd(CMD_WRITE_EXT_SCI_MASK, args, 2, NULL, 0);
+}
+
+static void olpc_xo175_ec_power_off(void)
+{
+	while (1) {
+		olpc_ec_cmd(CMD_POWER_OFF, NULL, 0, NULL, 0);
+		mdelay(1000);
+	}
+}
+
+static int __maybe_unused olpc_xo175_ec_suspend(struct device *dev)
+{
+	struct olpc_xo175_ec *priv = dev_get_drvdata(dev);
+	static struct {
+		u8 suspend;
+		u32 suspend_count;
+	} __packed hintargs;
+	static unsigned int suspend_count;
+
+	/*
+	 * SOC_SLEEP is not wired to the EC on B3 and earlier boards.
+	 * This command lets the EC know instead. The suspend count doesn't seem
+	 * to be used anywhere but in the EC debug output.
+	 */
+	hintargs.suspend = 1;
+	hintargs.suspend_count = suspend_count++;
+	olpc_ec_cmd(CMD_SUSPEND_HINT, (void *)&hintargs, sizeof(hintargs),
+								NULL, 0);
+
+	/*
+	 * After we've sent the suspend hint, don't allow further EC commands
+	 * to be run until we've resumed. Userspace tasks should be frozen,
+	 * but kernel threads and interrupts could still schedule EC commands.
+	 */
+	priv->suspended = true;
+
+	return 0;
+}
+
+static int __maybe_unused olpc_xo175_ec_resume_noirq(struct device *dev)
+{
+	struct olpc_xo175_ec *priv = dev_get_drvdata(dev);
+
+	priv->suspended = false;
+
+	return 0;
+}
+
+static int __maybe_unused olpc_xo175_ec_resume(struct device *dev)
+{
+	u8 x = 0;
+
+	/*
+	 * The resume hint is only needed if no other commands are
+	 * being sent during resume. all it does is tell the EC
+	 * the SoC is definitely awake.
+	 */
+	olpc_ec_cmd(CMD_SUSPEND_HINT, &x, 1, NULL, 0);
+
+	/* Enable all EC events while we're awake */
+	olpc_xo175_ec_set_event_mask(EC_ALL_EVENTS);
+
+	return 0;
+}
+
+static struct olpc_ec_driver olpc_xo175_ec_driver = {
+	.ec_cmd = olpc_xo175_ec_cmd,
+};
+
+static int olpc_xo175_ec_remove(struct spi_device *spi)
+{
+	if (pm_power_off == olpc_xo175_ec_power_off)
+		pm_power_off = NULL;
+
+	spi_slave_abort(spi);
+
+	platform_device_unregister(olpc_ec);
+	olpc_ec = NULL;
+
+	return 0;
+}
+
+static int olpc_xo175_ec_probe(struct spi_device *spi)
+{
+	struct olpc_xo175_ec *priv;
+	int ret;
+
+	if (olpc_ec) {
+		dev_err(&spi->dev, "OLPC EC already registered.\n");
+		return -EBUSY;
+	}
+
+	priv = devm_kzalloc(&spi->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->gpio_cmd = devm_gpiod_get(&spi->dev, "cmd", GPIOD_OUT_LOW);
+	if (IS_ERR(priv->gpio_cmd)) {
+		dev_err(&spi->dev, "failed to get cmd gpio: %ld\n",
+					PTR_ERR(priv->gpio_cmd));
+		return PTR_ERR(priv->gpio_cmd);
+	}
+
+	priv->spi = spi;
+
+	spin_lock_init(&priv->cmd_state_lock);
+	priv->cmd_state = CMD_STATE_IDLE;
+	init_completion(&priv->cmd_done);
+
+	priv->logbuf_len = 0;
+
+	/* Set up power button input device */
+	priv->pwrbtn = devm_input_allocate_device(&spi->dev);
+	if (!priv->pwrbtn)
+		return -ENOMEM;
+	priv->pwrbtn->name = "Power Button";
+	priv->pwrbtn->dev.parent = &spi->dev;
+	input_set_capability(priv->pwrbtn, EV_KEY, KEY_POWER);
+	ret = input_register_device(priv->pwrbtn);
+	if (ret) {
+		dev_err(&spi->dev, "error registering input device: %d\n", ret);
+		return ret;
+	}
+
+	spi_set_drvdata(spi, priv);
+
+	priv->xfer.rx_buf = &priv->rx_buf;
+	priv->xfer.tx_buf = &priv->tx_buf;
+
+	olpc_xo175_ec_read_packet(priv);
+
+	olpc_ec_driver_register(&olpc_xo175_ec_driver, priv);
+	olpc_ec = platform_device_register_resndata(&spi->dev, "olpc-ec", -1,
+							NULL, 0, NULL, 0);
+
+	/* Enable all EC events while we're awake */
+	olpc_xo175_ec_set_event_mask(EC_ALL_EVENTS);
+
+	if (pm_power_off == NULL)
+		pm_power_off = olpc_xo175_ec_power_off;
+
+	dev_info(&spi->dev, "OLPC XO-1.75 Embedded Controller driver\n");
+
+	return 0;
+}
+
+static const struct dev_pm_ops olpc_xo175_ec_pm_ops = {
+	SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(NULL, olpc_xo175_ec_resume_noirq)
+	SET_RUNTIME_PM_OPS(olpc_xo175_ec_suspend, olpc_xo175_ec_resume, NULL)
+};
+
+static const struct of_device_id olpc_xo175_ec_of_match[] = {
+	{ .compatible = "olpc,xo1.75-ec" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, olpc_xo175_ec_of_match);
+
+static struct spi_driver olpc_xo175_ec_spi_driver = {
+	.driver = {
+		.name	= "olpc-xo175-ec",
+		.of_match_table = olpc_xo175_ec_of_match,
+		.pm = &olpc_xo175_ec_pm_ops,
+	},
+	.probe		= olpc_xo175_ec_probe,
+	.remove		= olpc_xo175_ec_remove,
+};
+module_spi_driver(olpc_xo175_ec_spi_driver);
+
+MODULE_DESCRIPTION("OLPC XO-1.75 Embedded Controller driver");
+MODULE_AUTHOR("Lennert Buytenhek <buytenh@wantstofly.org>"); /* Functionality */
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>"); /* Bugs */
+MODULE_LICENSE("GPL");