Device migrations and driver implementations (#564)

Platforms/platform-esp32/bindings/espressif,esp32-spi.yaml

@@ -41,3 +41,11 @@ properties:
     element-type: "struct GpioPinSpec"
     default: "{ }"
     description: Null-terminated array of chip select GPIO pin specs for peripherals on this bus
+  miso-pull-up:
+    type: boolean
+    default: false
+    description: >
+      Enables a weak internal pull-up on MISO, which floats between transactions/while another
+      device on the bus is selected. Helps some SPI peripherals (a garbled/invalid response on
+      CMD8/if_cond has been observed for SD-over-SPI on some boards) but has been observed to
+      break others (prevents the SD card from responding to CMD0 at all) - opt in per board.

Platforms/platform-esp32/include/tactility/drivers/esp32_spi.h

@@ -27,6 +27,14 @@ struct Esp32SpiConfig {
     struct GpioPinSpec* cs_gpios;
     /** The item count of cs_gpios */
     uint8_t cs_gpios_count;
+    /**
+     * Enables a weak internal pull-up on MISO, which floats between transactions/while
+     * another device on the bus is selected. Helps some SPI peripherals (a garbled/invalid
+     * response on CMD8/if_cond has been observed for SD-over-SPI on some boards) but has been
+     * observed to break others (e.g. prevents the SD card from responding to CMD0 at all on
+     * some boards) - opt in per board rather than defaulting it on for everyone.
+     */
+    bool miso_pull_up;
 };
 
 /**

Platforms/platform-esp32/source/drivers/esp32_spi.cpp

@@ -129,8 +129,9 @@ static error_t start(Device* device) {
     // MISO is only actively driven by the selected slave; between commands (and briefly during
     // slave selection/response) it floats, which can be read as spurious bits. A weak pull-up
     // costs nothing against an actively-driven line and avoids that, e.g. on SD-over-SPI this
-    // shows up as CMD8/if_cond failing with a garbled/invalid response.
-    if (data->miso_descriptor != nullptr) {
+    // shows up as CMD8/if_cond failing with a garbled/invalid response. Opt-in per board though:
+    // it's been observed to instead prevent an SD card from responding to CMD0 at all elsewhere.
+    if (data->miso_descriptor != nullptr && dts_config->miso_pull_up) {
         gpio_descriptor_set_flags(data->miso_descriptor, GPIO_FLAG_DIRECTION_INPUT | GPIO_FLAG_PULL_UP);
     }