comments for Luminary ICDI layout

Provide $defines for more of the signals involved in the
Luminary ICDI hardware, and comment some of what's going on.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

diff --git a/src/jtag/drivers/ft2232.c b/src/jtag/drivers/ft2232.c
index bf71fa3237de6831ef5e1115ef64954f0ed3ee1b..4dcc045cccdeda67b4a0e2859e0cd1e5c056818a 100644 (file)
--- a/src/jtag/drivers/ft2232.c
+++ b/src/jtag/drivers/ft2232.c
@@ -318,6 +318,9 @@ static const struct ft2232_layout *layout;
 
 /** default bitmask values ddriven on DBUS: TCK/TDI/TDO/TMS and GPIOL(0..4) */
 static uint8_t                  low_output     = 0x0;
+
+/* note that direction bit == 1 means that signal is an output */
+
 /** default direction bitmask for DBUS: TCK/TDI/TDO/TMS and GPIOL(0..4) */
 static uint8_t                  low_direction  = 0x0;
 /** default value bitmask for CBUS GPIOH(0..4) */
@@ -2492,13 +2495,34 @@ static int icdi_jtag_init(void)
 
        /* Most Luminary eval boards support SWO trace output,
         * and should use this "luminary_icdi" layout.
+        *
+        * DBUS 0..3 are used for JTAG as usual.  GPIOs are used
+        * to switch between JTAG and SWD, or switch the ft2232 UART
+        * between (i) the target UART or (ii) SWO trace data.
+        *
+        * We come up in JTAG mode and may switch to SWD later (with
+        * SWO/trace option if SWD is active).
+        *
+        * DBUS == GPIO-Lx
+        * CBUS == GPIO-Hx
         */
+
+
+#define ICDI_JTAG_EN (1 << 7)          /* ADBUS 7 (a.k.a. DBGMOD) */
+#define ICDI_DBG_ENn (1 << 6)          /* ADBUS 6 */
+#define ICDI_SRST (1 << 5)             /* ADBUS 5 */
+#define ICDI_TDI (1 << 2)              /* ADBUS 2 (INPUT) */
+
+#define ICDI_SWO_EN (1 << 4)           /* BDBUS 4 */
+#define ICDI_TX_SWO (1 << 1)           /* BDBUS 1 */
+
        nTRST = 0x0;
        nTRSTnOE = 0x00;
-       nSRST = 0x20;
+       nSRST = ICDI_SRST;
        nSRSTnOE = 0x20;
-       low_output    = 0x88;
-       low_direction = 0xcb;
+
+       low_output    = 0x08 | ICDI_JTAG_EN;
+       low_direction = 0xcb | ICDI_JTAG_EN;
 
        return ftx232_dbus_write();
 }