[PATCH 3/4] platform/chrome: Add cros_ec_accel_legacy driver

[Thierry Escande]

From: Gwendal Grignou <gwendal@xxxxxxxxxxxx>

Add driver to support older EC firmware that only support deprecated
ec command. Rely on ACPI memory map register to access sensor
information.
Present same interface as the regular cros_ec sensor stack:
- one iio device per accelerometer
- use HTML5 axis definition
- use iio abi units
- accept calibration calls, but do nothing
Chrome can use the same code than regular cros_ec sensor stack to
calculate orientation and lid angle.

Signed-off-by: Gwendal Grignou <gwendal@xxxxxxxxxxxx>
Signed-off-by: Thierry Escande <thierry.escande@xxxxxxxxxxxxx>
---
 drivers/iio/accel/Kconfig                |  11 +
 drivers/iio/accel/Makefile               |   2 +
 drivers/iio/accel/cros_ec_accel_legacy.c | 444 +++++++++++++++++++++++++++++++
 3 files changed, 457 insertions(+)
 create mode 100644 drivers/iio/accel/cros_ec_accel_legacy.c

diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
index 15de262..5a1ef29 100644
--- a/drivers/iio/accel/Kconfig
+++ b/drivers/iio/accel/Kconfig
@@ -148,6 +148,17 @@ config HID_SENSOR_ACCEL_3D
 	  To compile this driver as a module, choose M here: the
 	  module will be called hid-sensor-accel-3d.
 
+config IIO_CROS_EC_ACCEL_LEGACY
+	tristate "ChromeOS EC Legacy Accelerometer Sensor"
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	select CROS_EC_LPC_REGISTER_DEVICE
+	help
+	  Say yes here to get support for accelerometers on Chromebook using
+	  legacy EC firmware.
+	  Sensor data is retrieved through IO memory.
+	  Newer devices should use IIO_CROS_EC_SENSORS.
+
 config IIO_ST_ACCEL_3AXIS
 	tristate "STMicroelectronics accelerometers 3-Axis Driver"
 	depends on (I2C || SPI_MASTER) && SYSFS
diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile
index 31fba19..fdd054a 100644
--- a/drivers/iio/accel/Makefile
+++ b/drivers/iio/accel/Makefile
@@ -43,6 +43,8 @@ obj-$(CONFIG_SCA3000)		+= sca3000.o
 obj-$(CONFIG_STK8312)		+= stk8312.o
 obj-$(CONFIG_STK8BA50)		+= stk8ba50.o
 
+obj-$(CONFIG_IIO_CROS_EC_ACCEL_LEGACY) += cros_ec_accel_legacy.o
+
 obj-$(CONFIG_IIO_SSP_SENSORS_COMMONS) += ssp_accel_sensor.o
 
 obj-$(CONFIG_IIO_ST_ACCEL_3AXIS) += st_accel.o
diff --git a/drivers/iio/accel/cros_ec_accel_legacy.c b/drivers/iio/accel/cros_ec_accel_legacy.c
new file mode 100644
index 0000000..26e71a1
--- /dev/null
+++ b/drivers/iio/accel/cros_ec_accel_legacy.c
@@ -0,0 +1,444 @@
+/*
+ * Driver for older Chrome OS EC accelerometer
+ *
+ * Copyright 2017 Google, Inc
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * This driver uses the memory mapper cros-ec interface to communicate
+ * with the Chrome OS EC about accelerometer data.
+ * Accelerometer access is presented through iio sysfs.
+ */
+
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/kfifo_buf.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/kernel.h>
+#include <linux/mfd/cros_ec.h>
+#include <linux/mfd/cros_ec_commands.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/platform_device.h>
+
+#define DRV_NAME	"cros-ec-accel-legacy"
+
+/* Indices for EC sensor values. */
+enum {
+	X,
+	Y,
+	Z,
+	MAX_AXIS,
+};
+
+struct cros_ec_accel_legacy_state;
+static ssize_t cros_ec_accel_legacy_id(struct iio_dev *indio_dev,
+				       uintptr_t private,
+				       const struct iio_chan_spec *chan,
+				       char *buf);
+
+static ssize_t cros_ec_accel_legacy_loc(struct iio_dev *indio_dev,
+					uintptr_t private,
+					const struct iio_chan_spec *chan,
+					char *buf);
+
+static const struct iio_chan_spec_ext_info cros_ec_accel_legacy_ext_info[] = {
+	{
+		.name = "id",
+		.shared = IIO_SHARED_BY_ALL,
+		.read = cros_ec_accel_legacy_id,
+	},
+	{
+		.name = "location",
+		.shared = IIO_SHARED_BY_ALL,
+		.read = cros_ec_accel_legacy_loc,
+	},
+	{ }
+};
+
+#define CROS_EC_ACCEL_LEGACY_CHAN(_axis)				\
+	{								\
+		.type = IIO_ACCEL,					\
+		.channel2 = IIO_MOD_X + (_axis),			\
+		.modified = 1,					        \
+		.info_mask_separate =					\
+			BIT(IIO_CHAN_INFO_RAW) |			\
+			BIT(IIO_CHAN_INFO_CALIBSCALE) |			\
+			BIT(IIO_CHAN_INFO_CALIBBIAS),			\
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE),	\
+		.ext_info = cros_ec_accel_legacy_ext_info,		\
+		.scan_type = {						\
+			.sign = 's',					\
+			.realbits = 16,					\
+			.storagebits = 16,				\
+			.shift = 0,					\
+		},							\
+	}								\
+
+static struct iio_chan_spec ec_accel_channels[] = {
+	CROS_EC_ACCEL_LEGACY_CHAN(X),
+	CROS_EC_ACCEL_LEGACY_CHAN(Y),
+	CROS_EC_ACCEL_LEGACY_CHAN(Z),
+	IIO_CHAN_SOFT_TIMESTAMP(MAX_AXIS)
+};
+
+/* State data for cros_ec_accel_legacy iio driver. */
+struct cros_ec_accel_legacy_state {
+	struct cros_ec_device *ec;
+
+	/*
+	 * Static array to hold data from a single capture. For each
+	 * channel we need 2 bytes, except for the timestamp. The timestamp
+	 * is always last and is always 8-byte aligned.
+	 */
+	union {
+		s16 samples[MAX_AXIS];
+		u64 ts[DIV_ROUND_UP(ARRAY_SIZE(ec_accel_channels),
+				    sizeof(u64) / sizeof(u16)) + 1];
+	} capture_data;
+	s8 sign[MAX_AXIS];
+	u8 sensor_num;
+};
+
+static int ec_cmd_read_u8(struct cros_ec_device *ec, unsigned int offset,
+			  u8 *dest)
+{
+	return ec->cmd_readmem(ec, offset, 1, dest);
+}
+
+static int ec_cmd_read_u16(struct cros_ec_device *ec, unsigned int offset,
+			   u16 *dest)
+{
+	u16 tmp;
+	int ret = ec->cmd_readmem(ec, offset, 2, &tmp);
+
+	*dest = le16_to_cpu(tmp);
+
+	return ret;
+}
+
+/**
+ * read_ec_until_not_busy - read from EC status byte until it reads not busy.
+ *
+ * @st Pointer to state information for device.
+ * @return 8-bit status if ok, -ve on error
+ */
+static int read_ec_until_not_busy(struct cros_ec_accel_legacy_state *st)
+{
+	struct cros_ec_device *ec = st->ec;
+	u8 status;
+	int attempts = 0;
+
+	ec_cmd_read_u8(ec, EC_MEMMAP_ACC_STATUS, &status);
+	while (status & EC_MEMMAP_ACC_STATUS_BUSY_BIT) {
+		/* Give up after enough attempts, return error. */
+		if (attempts++ >= 50)
+			return -EIO;
+
+		/* Small delay every so often. */
+		if (attempts % 5 == 0)
+			msleep(25);
+
+		ec_cmd_read_u8(ec, EC_MEMMAP_ACC_STATUS, &status);
+	}
+
+	return status;
+}
+
+/**
+ * read_ec_accel_data_unsafe - read acceleration data from EC shared memory.
+ *
+ * @st Pointer to state information for device.
+ * @scan_mask Bitmap of the sensor indices to scan.
+ * @data Location to store data.
+ *
+ * Note this is the unsafe function for reading the EC data. It does not
+ * guarantee that the EC will not modify the data as it is being read in.
+ */
+static void read_ec_accel_data_unsafe(struct cros_ec_accel_legacy_state *st,
+				      unsigned long scan_mask, s16 *data)
+{
+	int i = 0;
+	int num_enabled = bitmap_weight(&scan_mask, MAX_AXIS);
+
+	/*
+	 * Read all sensors enabled in scan_mask. Each value is 2
+	 * bytes.
+	 */
+	while (num_enabled--) {
+		i = find_next_bit(&scan_mask, MAX_AXIS, i);
+		ec_cmd_read_u16(
+			st->ec,
+			EC_MEMMAP_ACC_DATA +
+				sizeof(s16) *
+				(1 + i + st->sensor_num * MAX_AXIS),
+			data);
+		*data *= st->sign[i];
+		i++;
+		data++;
+	}
+}
+
+/**
+ * read_ec_accel_data - read acceleration data from EC shared memory.
+ *
+ * @st Pointer to state information for device.
+ * @scan_mask Bitmap of the sensor indices to scan.
+ * @data Location to store data.
+ * @return 0 if ok, -ve on error
+ *
+ * Note: this is the safe function for reading the EC data. It guarantees
+ * that the data sampled was not modified by the EC while being read.
+ */
+static int read_ec_accel_data(struct cros_ec_accel_legacy_state *st,
+			      unsigned long scan_mask, s16 *data)
+{
+	u8 samp_id = 0xff;
+	u8 status = 0;
+	int rv;
+	int attempts = 0;
+
+	/*
+	 * Continually read all data from EC until the status byte after
+	 * all reads reflects that the EC is not busy and the sample id
+	 * matches the sample id from before all reads. This guarantees
+	 * that data read in was not modified by the EC while reading.
+	 */
+	while ((status & (EC_MEMMAP_ACC_STATUS_BUSY_BIT |
+			  EC_MEMMAP_ACC_STATUS_SAMPLE_ID_MASK)) != samp_id) {
+		/* If we have tried to read too many times, return error. */
+		if (attempts++ >= 5)
+			return -EIO;
+
+		/* Read status byte until EC is not busy. */
+		rv = read_ec_until_not_busy(st);
+		if (rv < 0)
+			return rv;
+		status = rv;
+
+		/*
+		 * Store the current sample id so that we can compare to the
+		 * sample id after reading the data.
+		 */
+		samp_id = status & EC_MEMMAP_ACC_STATUS_SAMPLE_ID_MASK;
+
+		/* Read all EC data, format it, and store it into data. */
+		read_ec_accel_data_unsafe(st, scan_mask, data);
+
+		/* Read status byte. */
+		ec_cmd_read_u8(st->ec, EC_MEMMAP_ACC_STATUS, &status);
+	}
+
+	return 0;
+}
+
+static int cros_ec_accel_legacy_read(struct iio_dev *indio_dev,
+				     struct iio_chan_spec const *chan,
+				     int *val, int *val2, long mask)
+{
+	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
+	s16 data = 0;
+	int ret = IIO_VAL_INT;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = read_ec_accel_data(st, (1 << chan->scan_index), &data);
+		if (ret)
+			return ret;
+		*val = data;
+		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_SCALE:
+		/* Sensor scale hard coded at 10 bits per g. */
+		*val = 0;
+		*val2 = IIO_G_TO_M_S_2(1024);
+		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		/* Calibration not supported. */
+		*val = 0;
+		return IIO_VAL_INT;
+	default:
+		return -EINVAL;
+	}
+}
+
+static int cros_ec_accel_legacy_write(struct iio_dev *indio_dev,
+				      struct iio_chan_spec const *chan,
+				      int val, int val2, long mask)
+{
+	int ret = 0;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_CALIBBIAS:
+		/* Do nothing, to allow calibration script to work. */
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	return ret;
+}
+
+static const struct iio_info cros_ec_accel_legacy_info = {
+	.read_raw = &cros_ec_accel_legacy_read,
+	.write_raw = &cros_ec_accel_legacy_write,
+	.driver_module = THIS_MODULE,
+};
+
+/**
+ * accel_capture - the trigger handler function
+ *
+ * @irq: the interrupt number
+ * @p: private data - always a pointer to the poll func.
+ *
+ * On a trigger event occurring, if the pollfunc is attached then this
+ * handler is called as a threaded interrupt (and hence may sleep). It
+ * is responsible for grabbing data from the device and pushing it into
+ * the associated buffer.
+ */
+static irqreturn_t cros_ec_accel_legacy_capture(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
+
+	/* Clear capture data. */
+	memset(st->capture_data.samples, 0, sizeof(st->capture_data));
+
+	/*
+	 * Read data based on which channels are enabled in scan mask. Note
+	 * that on a capture we are always reading the calibrated data.
+	 */
+	read_ec_accel_data(st, *indio_dev->active_scan_mask,
+			   st->capture_data.samples);
+
+	/* Store the timestamp last 8 bytes of data. */
+	if (indio_dev->scan_timestamp)
+		st->capture_data.ts[(indio_dev->scan_bytes - 1) / sizeof(s64)] =
+			iio_get_time_ns(indio_dev);
+
+	iio_push_to_buffers(indio_dev, (u8 *)st->capture_data.samples);
+
+	/*
+	 * Tell the core we are done with this trigger and ready for the
+	 * next one.
+	 */
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+static char *cros_ec_accel_legacy_loc_strings[] = {
+	[MOTIONSENSE_LOC_BASE] = "base",
+	[MOTIONSENSE_LOC_LID] = "lid",
+	[MOTIONSENSE_LOC_MAX] = "unknown",
+};
+
+static ssize_t cros_ec_accel_legacy_loc(struct iio_dev *indio_dev,
+					uintptr_t private,
+					const struct iio_chan_spec *chan,
+					char *buf)
+{
+	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
+
+	return sprintf(buf, "%s\n",
+		       cros_ec_accel_legacy_loc_strings[st->sensor_num +
+							MOTIONSENSE_LOC_BASE]);
+}
+
+static ssize_t cros_ec_accel_legacy_id(struct iio_dev *indio_dev,
+				       uintptr_t private,
+				       const struct iio_chan_spec *chan,
+				       char *buf)
+{
+	struct cros_ec_accel_legacy_state *st = iio_priv(indio_dev);
+
+	return sprintf(buf, "%d\n", st->sensor_num);
+}
+
+static int cros_ec_accel_legacy_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cros_ec_dev *ec = dev_get_drvdata(dev->parent);
+	struct cros_ec_sensor_platform *sensor_platform = dev_get_platdata(dev);
+	struct iio_dev *indio_dev;
+	struct cros_ec_accel_legacy_state *state;
+	int ret, i;
+
+	if (!ec || !ec->ec_dev) {
+		dev_warn(&pdev->dev, "No EC device found.\n");
+		return -EINVAL;
+	}
+
+	if (!ec->ec_dev->cmd_readmem) {
+		dev_warn(&pdev->dev, "EC does not support direct reads.\n");
+		return -EINVAL;
+	}
+
+	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*state));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, indio_dev);
+	state = iio_priv(indio_dev);
+	state->ec = ec->ec_dev;
+	state->sensor_num = sensor_platform->sensor_num;
+
+	indio_dev->dev.parent = dev;
+	indio_dev->name = pdev->name;
+	indio_dev->channels = ec_accel_channels;
+	/*
+	 * Present the channel using HTML5 standard:
+	 * need to invert X and Y and invert some lid axis.
+	 */
+	for (i = X ; i < MAX_AXIS; i++) {
+		switch (i) {
+		case X:
+			ec_accel_channels[X].scan_index = Y;
+		case Y:
+			ec_accel_channels[Y].scan_index = X;
+		case Z:
+			ec_accel_channels[Z].scan_index = Z;
+		}
+		if (state->sensor_num == MOTIONSENSE_LOC_LID && i != Y)
+			state->sign[i] = -1;
+		else
+			state->sign[i] = 1;
+	}
+	indio_dev->num_channels = ARRAY_SIZE(ec_accel_channels);
+	indio_dev->dev.parent = &pdev->dev;
+	indio_dev->info = &cros_ec_accel_legacy_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
+					      cros_ec_accel_legacy_capture,
+					      NULL);
+	if (ret)
+		return ret;
+
+	return devm_iio_device_register(dev, indio_dev);
+}
+
+static struct platform_driver cros_ec_accel_platform_driver = {
+	.driver = {
+		.name	= DRV_NAME,
+	},
+	.probe		= cros_ec_accel_legacy_probe,
+};
+module_platform_driver(cros_ec_accel_platform_driver);
+
+MODULE_DESCRIPTION("ChromeOS EC legacy accelerometer driver");
+MODULE_AUTHOR("Gwendal Grignou <gwendal@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" DRV_NAME);
-- 
2.7.4