core: reset i2c bus when detected busy

core/embed/trezorhal/touch_t.h

@@ -91,16 +91,11 @@ void HAL_I2C_MspDeInit(I2C_HandleTypeDef *hi2c) {
   __HAL_RCC_I2C1_CLK_DISABLE();
 }
 
-void touch_power_on(void) {
+static void _i2c_init(void) {
   if (i2c_handle.Instance) {
     return;
   }
 
-  // turn on CTP circuitry
-  touch_active_pin_state();
-  HAL_Delay(50);
-
-  // I2C device interface configuration
   i2c_handle.Instance = I2C1;
   i2c_handle.Init.ClockSpeed = 400000;
   i2c_handle.Init.DutyCycle = I2C_DUTYCYCLE_16_9;
@@ -115,6 +110,84 @@ void touch_power_on(void) {
     ensure(secfalse, NULL);
     return;
   }
+}
+
+static void _i2c_deinit(void) {
+  if (i2c_handle.Instance) {
+    HAL_I2C_DeInit(&i2c_handle);
+    i2c_handle.Instance = NULL;
+  }
+}
+
+static void _i2c_ensure_pin(uint16_t GPIO_Pin, GPIO_PinState PinState) {
+  HAL_GPIO_WritePin(GPIOB, GPIO_Pin, PinState);
+  while (HAL_GPIO_ReadPin(GPIOB, GPIO_Pin) != PinState)
+    ;
+}
+
+// I2C cycle described in section 2.9.7 of STM CD00288116 Errata sheet
+//
+// https://www.st.com/content/ccc/resource/technical/document/errata_sheet/7f/05/b0/bc/34/2f/4c/21/CD00288116.pdf/files/CD00288116.pdf/jcr:content/translations/en.CD00288116.pdf
+
+static void _i2c_cycle(void) {
+  // PIN6 is SCL, PIN7 is SDA
+
+  // 1. Disable I2C peripheral
+  _i2c_deinit();
+
+  // 2. Configure SCL/SDA as GPIO OUTPUT Open Drain
+  GPIO_InitTypeDef GPIO_InitStructure;
+  GPIO_InitStructure.Mode = GPIO_MODE_OUTPUT_OD;
+  GPIO_InitStructure.Pull = GPIO_NOPULL;
+  GPIO_InitStructure.Speed = GPIO_SPEED_FREQ_LOW;
+  GPIO_InitStructure.Pin = GPIO_PIN_6 | GPIO_PIN_7;
+  HAL_GPIO_Init(GPIOB, &GPIO_InitStructure);
+  HAL_Delay(50);
+
+  // 3. Check SCL and SDA High level
+  _i2c_ensure_pin(GPIO_PIN_6, GPIO_PIN_SET);
+  _i2c_ensure_pin(GPIO_PIN_7, GPIO_PIN_SET);
+  // 4+5. Check SDA Low level
+  _i2c_ensure_pin(GPIO_PIN_7, GPIO_PIN_RESET);
+  // 6+7. Check SCL Low level
+  _i2c_ensure_pin(GPIO_PIN_6, GPIO_PIN_RESET);
+  // 8+9. Check SCL High level
+  _i2c_ensure_pin(GPIO_PIN_6, GPIO_PIN_SET);
+  // 10+11.  Check SDA High level
+  _i2c_ensure_pin(GPIO_PIN_7, GPIO_PIN_SET);
+
+  // 12. Configure SCL/SDA as Alternate function Open-Drain
+  GPIO_InitStructure.Mode = GPIO_MODE_AF_OD;
+  GPIO_InitStructure.Pull = GPIO_NOPULL;
+  GPIO_InitStructure.Speed = GPIO_SPEED_FREQ_LOW;
+  GPIO_InitStructure.Alternate = GPIO_AF4_I2C1;
+  GPIO_InitStructure.Pin = GPIO_PIN_6 | GPIO_PIN_7;
+  HAL_GPIO_Init(GPIOB, &GPIO_InitStructure);
+  HAL_Delay(50);
+
+  // 13. Set SWRST bit in I2Cx_CR1 register
+  __HAL_RCC_I2C1_FORCE_RESET();
+  HAL_Delay(50);
+
+  // 14. Clear SWRST bit in I2Cx_CR1 register
+  __HAL_RCC_I2C1_RELEASE_RESET();
+
+  // 15. Enable the I2C peripheral
+  _i2c_init();
+  HAL_Delay(10);
+}
+
+void touch_power_on(void) {
+  if (i2c_handle.Instance) {
+    return;
+  }
+
+  // turn on CTP circuitry
+  touch_active_pin_state();
+  HAL_Delay(50);
+
+  // I2C device interface configuration
+  _i2c_init();
 
   // set register 0xA4 G_MODE to interrupt polling mode (0x00). basically, CTPM
   // keeps this input line (to PC4) low while a finger is on the screen.
@@ -129,10 +202,7 @@ void touch_power_on(void) {
 }
 
 void touch_power_off(void) {
-  if (i2c_handle.Instance) {
-    HAL_I2C_DeInit(&i2c_handle);
-    i2c_handle.Instance = NULL;
-  }
+  _i2c_deinit();
   // turn off CTP circuitry
   HAL_Delay(50);
   touch_default_pin_state();
@@ -175,8 +245,10 @@ uint32_t touch_read(void) {
   }
 
   uint8_t outgoing[] = {0x00};  // start reading from address 0x00
-  if (HAL_OK != HAL_I2C_Master_Transmit(&i2c_handle, TOUCH_ADDRESS, outgoing,
-                                        sizeof(outgoing), 1)) {
+  int result = HAL_I2C_Master_Transmit(&i2c_handle, TOUCH_ADDRESS, outgoing,
+                                       sizeof(outgoing), 1);
+  if (result != HAL_OK) {
+    if (result == HAL_BUSY) _i2c_cycle();
     return 0;
   }