Improve I2C power-cycling logic:

We only power, clock and enable the peripepheral when / if we need it

* We no longer automatically turn on the SERIAL PD when the CM3 is running
* Make sure the I2C peripheral is accessible (powered and clocked) before any operation
* If the peripheral is not accessible, automatically power it up and run the clock
* Put SDA, SCL, SDA HP and SCL HP in a low-leakage state when shutting down
* Don't automatically fire up the I2C controller when we wake up

platform/srf06-cc26xx/sensortag/board-i2c.c

@@ -39,9 +39,55 @@
 #include "contiki-conf.h"
 #include "ti-lib.h"
 #include "board-i2c.h"
+#include "lpm.h"
+
+#include <string.h>
+#include <stdbool.h>
+/*---------------------------------------------------------------------------*/
+#define NO_INTERFACE 0xFF
 /*---------------------------------------------------------------------------*/
 static uint8_t slave_addr = 0x00;
-static uint8_t interface = 0xFF;
+static uint8_t interface = NO_INTERFACE;
+/*---------------------------------------------------------------------------*/
+static bool
+accessible(void)
+{
+  /* First, check the PD */
+  if(ti_lib_prcm_power_domain_status(PRCM_DOMAIN_SERIAL)
+     != PRCM_DOMAIN_POWER_ON) {
+    return false;
+  }
+
+  /* Then check the 'run mode' clock gate */
+  if(!(HWREG(PRCM_BASE + PRCM_O_I2CCLKGR) & PRCM_I2CCLKGR_CLK_EN)) {
+    return false;
+  }
+
+  return true;
+}
+/*---------------------------------------------------------------------------*/
+void
+board_i2c_wakeup()
+{
+  /* First, make sure the SERIAL PD is on */
+  ti_lib_prcm_power_domain_on(PRCM_DOMAIN_SERIAL);
+  while((ti_lib_prcm_power_domain_status(PRCM_DOMAIN_SERIAL)
+        != PRCM_DOMAIN_POWER_ON));
+
+  /* Enable the clock to I2C */
+  ti_lib_prcm_peripheral_run_enable(PRCM_PERIPH_I2C0);
+  ti_lib_prcm_load_set();
+  while(!ti_lib_prcm_load_get());
+
+  /* Reset the I2C controller */
+  HWREG(PRCM_BASE + PRCM_O_RESETI2C) = PRCM_RESETI2C_I2C;
+
+  /* Enable and initialize the I2C master module */
+  ti_lib_i2c_master_init_exp_clk(I2C0_BASE,
+                                 ti_lib_sys_ctrl_peripheral_clock_get(
+                                   PRCM_PERIPH_I2C0, SYSCTRL_SYSBUS_ON),
+                                 true);
+}
 /*---------------------------------------------------------------------------*/
 static bool
 i2c_status()
@@ -57,21 +103,34 @@ i2c_status()
 }
 /*---------------------------------------------------------------------------*/
 void
-board_i2c_init()
+board_i2c_shutdown()
 {
-  /* The I2C peripheral must be enabled */
+  interface = NO_INTERFACE;
-  ti_lib_prcm_peripheral_run_enable(PRCM_PERIPH_I2C0);
+
+  if(accessible()) {
+    ti_lib_i2c_master_disable(I2C0_BASE);
+  }
+
+  ti_lib_prcm_peripheral_run_disable(PRCM_PERIPH_I2C0);
   ti_lib_prcm_load_set();
   while(!ti_lib_prcm_load_get());
 
-  /* Reset the I2C controller */
+  /*
-  HWREG(PRCM_BASE + PRCM_O_RESETI2C) = PRCM_RESETI2C_I2C;
+   * Set all pins to GPIO Input and disable the output driver. Set internal
+   * pull to match external pull
+   *
+   * SDA and SCL: external PU resistor
+   * SDA HP and SCL HP: MPU PWR low
+   */
+  ti_lib_ioc_pin_type_gpio_input(BOARD_IOID_SDA_HP);
+  ti_lib_ioc_io_port_pull_set(BOARD_IOID_SDA_HP, IOC_IOPULL_DOWN);
+  ti_lib_ioc_pin_type_gpio_input(BOARD_IOID_SCL_HP);
+  ti_lib_ioc_io_port_pull_set(BOARD_IOID_SCL_HP, IOC_IOPULL_DOWN);
 
-  /* Enable and initialize the I2C master module */
+  ti_lib_ioc_pin_type_gpio_input(BOARD_IOID_SDA);
-  ti_lib_i2c_master_init_exp_clk(I2C0_BASE,
+  ti_lib_ioc_io_port_pull_set(BOARD_IOID_SDA, IOC_IOPULL_UP);
-                                 ti_lib_sys_ctrl_peripheral_clock_get(
+  ti_lib_ioc_pin_type_gpio_input(BOARD_IOID_SCL);
-                                   PRCM_PERIPH_I2C0, SYSCTRL_SYSBUS_ON),
+  ti_lib_ioc_io_port_pull_set(BOARD_IOID_SCL, IOC_IOPULL_UP);
-                                 true);
 }
 /*---------------------------------------------------------------------------*/
 bool
@@ -248,8 +307,15 @@ board_i2c_select(uint8_t new_interface, uint8_t address)
 {
   slave_addr = address;
 
+  if(accessible() == false) {
+    board_i2c_wakeup();
+  }
+
   if(new_interface != interface) {
     interface = new_interface;
+
+    ti_lib_i2c_master_disable(I2C0_BASE);
+
     if(interface == BOARD_I2C_INTERFACE_0) {
       ti_lib_ioc_io_port_pull_set(BOARD_IOID_SDA, IOC_NO_IOPULL);
       ti_lib_ioc_io_port_pull_set(BOARD_IOID_SCL, IOC_NO_IOPULL);
@@ -263,6 +329,12 @@ board_i2c_select(uint8_t new_interface, uint8_t address)
       ti_lib_ioc_pin_type_gpio_input(BOARD_IOID_SDA);
       ti_lib_ioc_pin_type_gpio_input(BOARD_IOID_SCL);
     }
+
+    /* Enable and initialize the I2C master module */
+    ti_lib_i2c_master_init_exp_clk(I2C0_BASE,
+                                   ti_lib_sys_ctrl_peripheral_clock_get(
+                                     PRCM_PERIPH_I2C0, SYSCTRL_SYSBUS_ON),
+                                   true);
   }
 }
 /*---------------------------------------------------------------------------*/

platform/srf06-cc26xx/sensortag/board-i2c.h

@@ -101,6 +101,27 @@ bool board_i2c_write_single(uint8_t data);
  */
 bool board_i2c_write_read(uint8_t *wdata, uint8_t wlen, uint8_t *rdata,
                           uint8_t rlen);
+
+/**
+ * \brief Enables the I2C peripheral with defaults
+ *
+ * This function is called to wakeup and initialise the I2C.
+ *
+ * This function can be called explicitly, but it will also be called
+ * automatically by board_i2c_select() when required. One of those two
+ * functions MUST be called before any other I2C operation after a chip
+ * sleep / wakeup cycle or after a call to board_i2c_shutdown(). Failing to do
+ * so will lead to a bus fault.
+ */
+void board_i2c_wakeup(void);
+
+/**
+ * \brief Stops the I2C peripheral and restores pins to s/w control
+ *
+ * This function is called automatically by the board's LPM logic, but it
+ * can also be called explicitly.
+ */
+void board_i2c_shutdown(void);
 /*---------------------------------------------------------------------------*/
 #endif /* BOARD_I2C_H_ */
 /*---------------------------------------------------------------------------*/

platform/srf06-cc26xx/sensortag/board.c

@@ -65,8 +65,6 @@ static void
 lpm_wakeup_handler(void)
 {
   power_domains_on();
-
-  board_i2c_init();
 }
 /*---------------------------------------------------------------------------*/
 static void
@@ -80,6 +78,9 @@ shutdown_handler(uint8_t mode)
     SENSORS_DEACTIVATE(hdc_1000_sensor);
     mpu_9250_sensor.configure(MPU_9250_SENSOR_SHUTDOWN, 0);
   }
+
+  /* In all cases, stop the I2C */
+  board_i2c_shutdown();
 }
 /*---------------------------------------------------------------------------*/
 /*
@@ -125,7 +126,6 @@ board_init()
   ti_lib_ioc_io_port_pull_set(BOARD_IOID_KEY_RIGHT, IOC_IOPULL_UP);
 
   /* I2C controller */
-  board_i2c_init();
 
   /* Sensor interface */
   ti_lib_rom_ioc_pin_type_gpio_input(BOARD_IOID_MPU_INT);
@@ -139,6 +139,7 @@ board_init()
   /* Flash interface */
   ti_lib_rom_ioc_pin_type_gpio_output(BOARD_IOID_FLASH_CS);
   ti_lib_gpio_pin_write(BOARD_FLASH_CS, 1);
+  board_i2c_wakeup();
 
   buzzer_init();