Unsuccessful attempt to use spi as swd tap.

components/blackmagic/CMakeLists.txt

@@ -2,6 +2,7 @@ set(BM_DIR "blackmagic-fw")
 set(PLATFORM_DIR "esp32-platform")
 
 set(BM_SOURCES 
+    # ${PLATFORM_DIR}/custom/swd-spi-tap.c
     ${BM_DIR}/src/platforms/common/swdptap.c
     ${BM_DIR}/src/platforms/common/jtagtap.c
     ${BM_DIR}/src/gdb_main.c

components/blackmagic/esp32-platform/custom/swd-spi-tap.c

@@ -0,0 +1,134 @@
+/**
+ * @file swd-spi-tap.c
+ * Does not work due to bug with switching 3-wire mode to RX.
+ * 
+ * https://github.com/espressif/esp-idf/issues/7800
+ * 
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <adiv5.h>
+
+#include <esp_log.h>
+#include <driver/spi_master.h>
+#include "../platform.h"
+#include <string.h>
+
+#define SWDTAP_DEBUG 0
+
+typedef enum {
+    SpiSwdDirFloat,
+    SpiSwdDirDrive,
+} SpiSwdDirection;
+
+static bool spi_bus_initialized = false;
+static spi_device_handle_t swd_spi_device;
+
+inline static void swd_spi_transmit(spi_transaction_t* swd_spi_transaction) {
+    ESP_ERROR_CHECK(spi_device_polling_transmit(swd_spi_device, swd_spi_transaction));
+}
+
+inline static uint32_t swd_spi_rx(int ticks) {
+    uint32_t data = 0;
+    spi_transaction_t swd_spi_transaction = {
+        .rxlength = ticks,
+        .tx_buffer = NULL,
+        .rx_buffer = &data,
+    };
+
+    swd_spi_transmit(&swd_spi_transaction);
+
+#if SWDTAP_DEBUG == 1
+    ESP_LOGW("spi_rx", "< [%02u] 0x%08x", ticks, data);
+#endif
+
+    return data;
+}
+
+inline static void swd_spi_tx(uint32_t data, int ticks) {
+    spi_transaction_t swd_spi_transaction = {
+        .length = ticks,
+        .tx_buffer = &data,
+        .rx_buffer = NULL,
+    };
+
+    swd_spi_transmit(&swd_spi_transaction);
+
+#if SWDTAP_DEBUG == 1
+    ESP_LOGI("spi_tx", "> [%02u] 0x%08x", ticks, data);
+#endif
+}
+
+static void swdspitap_turnaround(SpiSwdDirection direction) {
+    static SpiSwdDirection old_direction = SpiSwdDirFloat;
+
+    if(direction == old_direction) return;
+    old_direction = direction;
+
+    swd_spi_tx(1, 1);
+}
+
+static uint32_t swdspitap_seq_in(int ticks) {
+    swdspitap_turnaround(SpiSwdDirFloat);
+    return swd_spi_rx(ticks);
+}
+
+static bool swdspitap_seq_in_parity(uint32_t* ret, int ticks) {
+    swdspitap_turnaround(SpiSwdDirFloat);
+    *ret = swd_spi_rx(ticks);
+    int parity = __builtin_popcount(*ret);
+    uint32_t data = swd_spi_rx(1);
+    parity += (data & 1);
+    swdspitap_turnaround(SpiSwdDirDrive);
+    return (parity & 1);
+}
+
+static void swdspitap_seq_out(uint32_t MS, int ticks) {
+    swdspitap_turnaround(SpiSwdDirDrive);
+    swd_spi_tx(MS, ticks);
+}
+
+static void swdspitap_seq_out_parity(uint32_t MS, int ticks) {
+    int parity = __builtin_popcount(MS);
+    swdspitap_turnaround(SpiSwdDirDrive);
+    swd_spi_tx(MS, ticks);
+    swd_spi_tx(parity & 1, 1);
+}
+
+int swdptap_init(ADIv5_DP_t* dp) {
+    if(!spi_bus_initialized) {
+        // config bus
+        spi_bus_config_t swd_spi_pins = {
+            .mosi_io_num = SWDIO_PIN, // SWD I/O
+            .miso_io_num = -1,
+            .sclk_io_num = SWCLK_PIN, // SWD CLK
+            .quadwp_io_num = -1,
+            .quadhd_io_num = -1,
+        };
+        ESP_ERROR_CHECK(spi_bus_initialize(HSPI_HOST, &swd_spi_pins, SPI_DMA_DISABLED));
+
+        // add device to bus with config
+        spi_device_interface_config_t swd_spi_config = {
+            .mode = 0,
+            .clock_speed_hz = 10 * 1000,
+            .spics_io_num = -1,
+            .flags = SPI_DEVICE_3WIRE | SPI_DEVICE_HALFDUPLEX | SPI_DEVICE_BIT_LSBFIRST,
+            .queue_size = 24,
+            .pre_cb = NULL,
+            .post_cb = NULL,
+        };
+        ESP_ERROR_CHECK(spi_bus_add_device(HSPI_HOST, &swd_spi_config, &swd_spi_device));
+
+        spi_bus_initialized = true;
+    }
+
+    // set functions
+    dp->seq_in = swdspitap_seq_in;
+    dp->seq_in_parity = swdspitap_seq_in_parity;
+    dp->seq_out = swdspitap_seq_out;
+    dp->seq_out_parity = swdspitap_seq_out_parity;
+
+    return 0;
+}