rp2040: allow board to customize pin reset state

.. and use it on usb host feather to set the reset state of the USB
power pin to "output high", while leaving it possible to create
a DigitalInOut of this pin from CircuitPython code.

Author: jepler

ports/raspberrypi/boards/adafruit_feather_rp2040_usb_host/board.c

@@ -28,15 +28,26 @@
 
 #include "shared-bindings/digitalio/DigitalInOut.h"
 #include "shared-bindings/usb_host/Port.h"
+#include "hardware/gpio.h"
 
 // Use the MP_WEAK supervisor/shared/board.c versions of routines not defined here.
 
 digitalio_digitalinout_obj_t _host_power;
 
-void board_init(void) {
-    common_hal_digitalio_digitalinout_construct(&_host_power, &pin_GPIO18);
-    common_hal_digitalio_digitalinout_never_reset(&_host_power);
-    common_hal_digitalio_digitalinout_switch_to_output(&_host_power, true, DRIVE_MODE_PUSH_PULL);
+bool board_reset_pin_number(uint8_t pin_number) {
+    if (pin_number == 18) {
+        // doing this (rather than gpio_init) in this specific order ensures no
+        // glitch if pin was already configured as a high output. gpio_init() temporarily
+        // configures the pin as an input, so the power enable value would potentially
+        // glitch.
+        gpio_put(pin_number, 1);
+        gpio_set_dir(pin_number, GPIO_OUT);
+        gpio_set_function(pin_number, GPIO_FUNC_SIO);
 
+        return true;
+    }
+    return false;
+}
+void board_init(void) {
     common_hal_usb_host_port_construct(&pin_GPIO16, &pin_GPIO17);
 }

ports/raspberrypi/common-hal/microcontroller/Pin.c

@@ -73,6 +73,11 @@ void never_reset_pin_number(uint8_t pin_number) {
     never_reset_pins |= 1 << pin_number;
 }
 
+// By default, all pins get reset in the same way
+MP_WEAK bool board_reset_pin_number(uint8_t pin_number) {
+    return false;
+}
+
 void reset_pin_number(uint8_t pin_number) {
     if (pin_number >= NUM_BANK0_GPIOS) {
         return;
@@ -81,6 +86,11 @@ void reset_pin_number(uint8_t pin_number) {
     gpio_bank0_pin_claimed &= ~(1 << pin_number);
     never_reset_pins &= ~(1 << pin_number);
 
+    // Allow the board to override the reset state of any pin
+    if (board_reset_pin_number(pin_number)) {
+        return;
+    }
+
     // We are very aggressive in shutting down the pad fully. Both pulls are
     // disabled and both buffers are as well.
     gpio_init(pin_number);

ports/raspberrypi/common-hal/microcontroller/Pin.h

@@ -34,6 +34,12 @@
 
 #include "peripherals/pins.h"
 
+// If a board needs a different reset state for one or more pins, implement
+// board_reset_pin_number so that it sets this state and returns `true` for those
+// pin numbers, `false` for others.
+// A default weak implementation always returns `false`.
+bool board_reset_pin_number(uint8_t pin_number);
+
 void reset_all_pins(void);
 // reset_pin_number takes the pin number instead of the pointer so that objects don't
 // need to store a full pointer.