Merge pull request #946 from lukash/imu-high-prio

imu: Raise the IMU thread priority to NORMALPRIO+2 on HW transports

Author: vedderb

imu/imu_thread.c

@@ -136,7 +136,10 @@ void imu_thread_start(void (*cb)(float *accel, float *gyro, float *mag, float dt
 		m_dev->interface->enable_drdy_output(m_dev, true);
 	}
 
-	m_thd = chThdCreateStatic(m_wa, sizeof(m_wa), NORMALPRIO, thread_func, NULL);
+	// Run above NORMALPRIO threads and the CAN read thread (NORMALPRIO + 1) when the
+	// transport allows it (is not CPU-heavy).
+	tprio_t prio = m_dev->transport->interface->cpu_bound ? NORMALPRIO : NORMALPRIO + 2;
+	m_thd = chThdCreateStatic(m_wa, sizeof(m_wa), prio, thread_func, NULL);
 }
 
 void imu_thread_stop(void) {

imu/transport.h

@@ -44,6 +44,10 @@ typedef struct transport transport_t;
 typedef struct {
 	// Human-readable transport name for diagnostics, e.g. "i2c-bb".
 	const char *name;
+	// True when a transfer occupies the CPU for its whole duration (bit-banged
+	// buses) and takes long to complete. Decides whether the IMU thread can
+	// run above NORMALPRIO.
+	bool cpu_bound;
 	// Highest sample rate (Hz) this bus may be driven at. Setting too high
 	// sample rate has caused rare unexplained MCU resets, probably due to CPU
 	// saturation. Each bus should set a safe maximum.

imu/transport_i2c_bb.c

@@ -50,6 +50,7 @@ static uint16_t max_sample_rate(transport_t *t) {
 
 static const transport_interface_t i2c_bb_interface = {
 	.name = "i2c-bb",
+	.cpu_bound = true,
 	.max_sample_rate = max_sample_rate,
 	.read_reg = read_reg,
 	.write_reg = write_reg,

imu/transport_spi_bb.c

@@ -68,6 +68,7 @@ static uint16_t max_sample_rate(transport_t *t) {
 
 static const transport_interface_t spi_bb_interface = {
 	.name = "spi-bb",
+	.cpu_bound = true,
 	.max_sample_rate = max_sample_rate,
 	.read_reg = read_reg,
 	.write_reg = write_reg,

imu/transport_spi_hw.c

@@ -107,6 +107,7 @@ static void deinit(transport_t *t) {
 
 static const transport_interface_t spi_hw_interface = {
 	.name = "spi-hw",
+	.cpu_bound = false,
 	.max_sample_rate = max_sample_rate,
 	.read_reg = read_reg,
 	.write_reg = write_reg,