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Subject[PATCH v4 3/4] platform/chrome: Add cros_ec_accel_legacy driver
Date
From: Gwendal Grignou <gwendal@chromium.org>

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@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
---
Documentation/ABI/testing/sysfs-bus-iio-cros-ec | 10 +
drivers/iio/accel/Kconfig | 11 +
drivers/iio/accel/Makefile | 2 +
drivers/iio/accel/cros_ec_accel_legacy.c | 425 ++++++++++++++++++++++++
4 files changed, 448 insertions(+)
create mode 100644 drivers/iio/accel/cros_ec_accel_legacy.c

diff --git a/Documentation/ABI/testing/sysfs-bus-iio-cros-ec b/Documentation/ABI/testing/sysfs-bus-iio-cros-ec
index 297b972..0e95c2c 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio-cros-ec
+++ b/Documentation/ABI/testing/sysfs-bus-iio-cros-ec
@@ -16,3 +16,13 @@ Description:
the motion sensor is placed. For example, in a laptop a motion
sensor can be located on the base or on the lid. Current valid
values are 'base' and 'lid'.
+
+What: /sys/bus/iio/devices/iio:deviceX/id
+Date: Septembre 2017
+KernelVersion: 4.14
+Contact: linux-iio@vger.kernel.org
+Description:
+ This attribute is exposed by the CrOS EC legacy accelerometer
+ driver and represents the sensor ID as exposed by the EC. This
+ ID is used by the Android sensor service hardware abstraction
+ layer (sensor HAL) through the Android container on ChromeOS.
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..be13f2a
--- /dev/null
+++ b/drivers/iio/accel/cros_ec_accel_legacy.c
@@ -0,0 +1,425 @@
+/*
+ * 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"
+
+/*
+ * Sensor scale hard coded at 10 bits per g, computed as:
+ * g / (2^10 - 1) = 0.009586168; with g = 9.80665 m.s^-2
+ */
+#define ACCEL_LEGACY_NSCALE 9586168
+
+/* Indices for EC sensor values. */
+enum {
+ X,
+ Y,
+ Z,
+ MAX_AXIS,
+};
+
+/* State data for cros_ec_accel_legacy iio driver. */
+struct cros_ec_accel_legacy_state {
+ struct cros_ec_device *ec;
+
+ /*
+ * Array holding data from a single capture. 2 bytes per channel
+ * for the 3 channels plus the timestamp which is always last and
+ * 8-bytes aligned.
+ */
+ s16 capture_data[8];
+ 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.
+ *
+ * This function reads EC status until its busy bit gets cleared. It does not
+ * wait indefinitely and returns -EIO if the EC status is still busy after a
+ * few hundreds milliseconds.
+ *
+ * Return: 8-bit status if ok, -EIO 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.
+ *
+ * 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.
+ *
+ * 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.
+ *
+ * Return: 0 if ok, -ve on error
+ */
+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 ret;
+ 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. */
+ ret = read_ec_until_not_busy(st);
+ if (ret < 0)
+ return ret;
+ status = ret;
+
+ /*
+ * 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:
+ *val = 0;
+ *val2 = ACCEL_LEGACY_NSCALE;
+ return IIO_VAL_INT_PLUS_NANO;
+ 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)
+{
+ /*
+ * Do nothing but don't return an error code to allow calibration
+ * script to work.
+ */
+ if (mask == IIO_CHAN_INFO_CALIBBIAS)
+ return 0;
+
+ return -EINVAL;
+}
+
+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,
+};
+
+/**
+ * cros_ec_accel_legacy_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.
+ *
+ * Return: IRQ_HANDLED
+ */
+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, 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);
+
+ iio_push_to_buffers_with_timestamp(indio_dev, (void *)st->capture_data,
+ iio_get_time_ns(indio_dev));
+
+ /*
+ * 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 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_SCALE) | \
+ 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, \
+ }, \
+ } \
+
+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)
+};
+
+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@chromium.org>");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" DRV_NAME);
--
2.7.4
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