zephyr: emul: set/read accel data support for LIS2DW12 emulator

Add support to the LIS2DW12 emulator for the following. This is needed
by an upcoming driver unit test for reading data from the sensor

 * Add support for reading the status and output data registers via I2C.
   Multi-byte reads are supported for the data regs. All of these will
   assert if written to because they are listed as read-only.
 * Add two new emulator control functions:
   * lis2dw12_emul_set_accel_reading - Allows the test to set a fake
     accelerometer reading. The X, Y, Z values are copied in to the
     internal register store in the appropriate format. The data ready
     bit in the status register is set.
   * lis2dw12_emul_clear_accel_reading - Reset the data registers to
     0 and clear the data ready flag.
 * Add macro definitions for the min and max acceleromter values. These
   are used for validating readings passed to
   lis2dw12_emul_set_accel_reading().

BRANCH=None
BUG=b:200046770
TEST=zmake -D configure --test test-drivers; make runhosttests

Signed-off-by: Tristan Honscheid <honscheid@google.com>
Change-Id: I56c93677e3e5d067f070d9b3fd98e2b25f80eac7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3318818
Reviewed-by: Denis Brockus <dbrockus@chromium.org>

3 files changed, 114 insertions, 0 deletions

diff --git a/driver/accel_lis2dw12.h b/driver/accel_lis2dw12.h
index 71116cb13b..9d0be0ac0a 100644
--- a/driver/accel_lis2dw12.h
+++ b/driver/accel_lis2dw12.h
@@ -45,6 +45,11 @@
 #define LIS2DW12_FIFO_THS_UP		0x80
 
 #define LIS2DW12_OUT_X_L_ADDR		0x28
+#define LIS2DW12_OUT_X_H_ADDR		0x29
+#define LIS2DW12_OUT_Y_L_ADDR		0x2a
+#define LIS2DW12_OUT_Y_H_ADDR		0x2b
+#define LIS2DW12_OUT_Z_L_ADDR		0x2c
+#define LIS2DW12_OUT_Z_H_ADDR		0x2d
 
 #define LIS2DW12_FIFO_CTRL_ADDR		0x2e
 
@@ -206,6 +211,12 @@ enum lis2dw12_fs {
  */
 #define LIS2DW12_RESOLUTION		14
 
+/** Maximum possible sample */
+#define LIS2DW12_SAMPLE_MAX		((1<<(LIS2DW12_RESOLUTION-1))-1)
+
+/** Smallest possible sample */
+#define LIS2DW12_SAMPLE_MIN		(-(1<<(LIS2DW12_RESOLUTION-1)))
+
 #ifdef CONFIG_ZTEST
 int lis2dw12_set_power_mode(const struct motion_sensor_t *s,
 			    enum lis2sw12_mode mode,
diff --git a/zephyr/emul/emul_lis2dw12.c b/zephyr/emul/emul_lis2dw12.c
index 3a29b74816..a4e6b46413 100644
--- a/zephyr/emul/emul_lis2dw12.c
+++ b/zephyr/emul/emul_lis2dw12.c
@@ -35,8 +35,12 @@ struct lis2dw12_emul_data {
 	uint8_t ctrl2_reg;
 	/** Emulated ctrl6 register */
 	uint8_t ctrl6_reg;
+	/** Emulated status register */
+	uint8_t status_reg;
 	/** Soft reset count */
 	uint32_t soft_reset_count;
+	/** Current X, Y, and Z output data registers */
+	int16_t accel_data[3];
 };
 
 struct lis2dw12_emul_cfg {
@@ -63,8 +67,13 @@ void lis2dw12_emul_reset(const struct emul *emul)
 	i2c_common_emul_set_read_func(i2c_emul, NULL, NULL);
 	i2c_common_emul_set_write_func(i2c_emul, NULL, NULL);
 	data->who_am_i_reg = LIS2DW12_WHO_AM_I;
+	data->ctrl1_reg = 0;
 	data->ctrl2_reg = 0;
+	data->ctrl6_reg = 0;
+	data->status_reg = 0;
 	data->soft_reset_count = 0;
+
+	memset(data->accel_data, 0, sizeof(data->accel_data));
 }
 
 void lis2dw12_emul_set_who_am_i(const struct emul *emul, uint8_t who_am_i)
@@ -103,6 +112,38 @@ static int lis2dw12_emul_read_byte(struct i2c_emul *emul, int reg, uint8_t *val,
 		__ASSERT_NO_MSG(bytes == 0);
 		*val = data->ctrl6_reg;
 		break;
+	case LIS2DW12_STATUS_REG:
+		__ASSERT_NO_MSG(bytes == 0);
+		*val = data->status_reg;
+		break;
+	case LIS2DW12_OUT_X_L_ADDR:
+	case LIS2DW12_OUT_X_H_ADDR:
+	case LIS2DW12_OUT_Y_L_ADDR:
+	case LIS2DW12_OUT_Y_H_ADDR:
+	case LIS2DW12_OUT_Z_L_ADDR:
+	case LIS2DW12_OUT_Z_H_ADDR:
+		/* Allow multi-byte reads within this range of registers.
+		 * `bytes` is actually an offset past the starting register
+		 * `reg`.
+		 */
+
+		__ASSERT_NO_MSG(LIS2DW12_OUT_X_L_ADDR + bytes <=
+				LIS2DW12_OUT_Z_H_ADDR);
+
+		/* 0 is OUT_X_L_ADDR .. 5 is OUT_Z_H_ADDR */
+		int offset_into_odrs = reg - LIS2DW12_OUT_X_L_ADDR + bytes;
+
+		/* Which of the 3 channels we're reading. 0 = X, 1 = Y, 2 = Z */
+		int channel = offset_into_odrs / 2;
+
+		if (offset_into_odrs % 2 == 0) {
+			/* Get the LSB (L reg) */
+			*val = data->accel_data[channel] & 0xFF;
+		} else {
+			/* Get the MSB (H reg) */
+			*val = (data->accel_data[channel] >> 8) & 0xFF;
+		}
+		break;
 	default:
 		__ASSERT(false, "No read handler for register 0x%02x", reg);
 		return -EINVAL;
@@ -175,6 +216,20 @@ static int lis2dw12_emul_write_byte(struct i2c_emul *emul, int reg, uint8_t val,
 	case LIS2DW12_CTRL6_ADDR:
 		data->ctrl6_reg = val;
 		break;
+	case LIS2DW12_STATUS_REG:
+		__ASSERT(false,
+			 "Attempt to write to read-only status register");
+		return -EINVAL;
+	case LIS2DW12_OUT_X_L_ADDR:
+	case LIS2DW12_OUT_X_H_ADDR:
+	case LIS2DW12_OUT_Y_L_ADDR:
+	case LIS2DW12_OUT_Y_H_ADDR:
+	case LIS2DW12_OUT_Z_L_ADDR:
+	case LIS2DW12_OUT_Z_H_ADDR:
+		__ASSERT(false,
+			 "Attempt to write to data output register 0x%02x",
+			 reg);
+		return -EINVAL;
 	default:
 		__ASSERT(false, "No write handler for register 0x%02x", reg);
 		return -EINVAL;
@@ -199,6 +254,37 @@ static int emul_lis2dw12_init(const struct emul *emul,
 	return i2c_emul_register(parent, emul->dev_label, &data->common.emul);
 }
 
+int lis2dw12_emul_set_accel_reading(const struct emul *emul, intv3_t reading)
+{
+	__ASSERT(emul, "emul is NULL");
+	struct lis2dw12_emul_data *data = emul->data;
+
+	for (int i = X; i <= Z; i++) {
+		/* Ensure we fit in a 14-bit signed integer */
+		if (reading[i] < LIS2DW12_SAMPLE_MIN ||
+		    reading[i] > LIS2DW12_SAMPLE_MAX) {
+			return -EINVAL;
+		}
+		/* Readings are left-aligned, so shift over by 2 */
+		data->accel_data[i] = reading[i] * 4;
+	}
+
+	/* Set the DRDY (data ready) bit */
+	data->status_reg |= LIS2DW12_STS_DRDY_UP;
+
+	return 0;
+}
+
+void lis2dw12_emul_clear_accel_reading(const struct emul *emul)
+{
+	__ASSERT(emul, "emul is NULL");
+	struct lis2dw12_emul_data *data = emul->data;
+
+	/* Zero out the registers and reset DRDY bit */
+	memset(data->accel_data, 0, sizeof(data->accel_data));
+	data->status_reg &= ~LIS2DW12_STS_DRDY_UP;
+}
+
 #define INIT_LIS2DW12(n)                                                  \
 	static struct lis2dw12_emul_data lis2dw12_emul_data_##n = {       \
 		.common = {                                               \
diff --git a/zephyr/include/emul/emul_lis2dw12.h b/zephyr/include/emul/emul_lis2dw12.h
index 91ad5c0948..0d630af215 100644
--- a/zephyr/include/emul/emul_lis2dw12.h
+++ b/zephyr/include/emul/emul_lis2dw12.h
@@ -80,4 +80,21 @@ uint8_t lis2dw12_emul_peek_mode(struct i2c_emul *emul);
  */
 uint8_t lis2dw12_emul_peek_lpmode(struct i2c_emul *emul);
 
+/**
+ * @brief Updates the current 3-axis acceleromter reading and
+ *        sets the DRDY (data ready) flag.
+ * @param emul Reference to current LIS2DW12 emulator.
+ * @param reading array of int X, Y, and Z readings.
+ * @return 0 on success, or -EINVAL if readings are out of bounds.
+ */
+int lis2dw12_emul_set_accel_reading(const struct emul *emul,
+				    intv3_t reading);
+
+/**
+ * @brief Clears the current accelerometer reading and resets the
+ *        DRDY (data ready) flag.
+ * @param emul Reference to current LIS2DW12 emulator.
+ */
+void lis2dw12_emul_clear_accel_reading(const struct emul *emul);
+
 #endif /* ZEPHYR_INCLUDE_EMUL_EMUL_LIS2DW12_H_ */