machine: add the "hifive_unleashed" machine data configuration method

Add a "hifive_unleashed" machine data configuration method.  This can
be used when the output BBL image is explicitly targeted for the
SiFive HiFive Unleashed board with the FU540-C000 SoC.  The primary
virtue of this configuration method is that it does not rely on DT
parsing at all.  BBL will pass whatever DTB it was given to the
operating system kernel, without trying to parse or edit it.

machine/configure-hifive-unleashed.c

@@ -0,0 +1,68 @@
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include "common.h"
+#include "config.h"
+#include "disabled_hart_mask.h"
+#include "fdt.h"
+#include "fdtutil.h"
+#include "htif.h"
+#include "mtrap.h"
+#include "probe.h"
+#include "uart.h"
+#include "uart16550.h"
+
+//////////////////////////////////////////// MEMORY SCAN /////////////////////////////////////////
+
+
+static void query_mem(void *context)
+{
+  mem_size = 0x200000000; /* 8GiB on the HiFive Unleashed */
+}
+
+///////////////////////////////////////////// SOC SCAN /////////////////////////////////////////
+
+static void query_soc(void *context)
+{
+  uintptr_t clint_base = 0x2000000;
+  int hart_count = 5;
+
+  plic_ndevs = 53;
+  hart_mask |= (1 << hart_count) - 1; /* 5 harts on the FU540 */
+  disabled_hart_mask = 0x1; /* hart 0, the E51 core */
+
+  common_setup_soc(clint_base, hart_count);
+}
+
+///////////////////////////////////////////// PLIC SCAN /////////////////////////////////////////
+
+static void query_plic(void *context)
+{
+  common_setup_plic(0xc000000); /* PLIC address */
+}
+
+
+//////////////////////////// UART //////////////////////////////
+
+static void query_uart(void *context)
+{
+  // Enable Rx/Tx channels
+  uart = (void *)0x10010000;
+  uart_enable_rx_tx();
+}
+
+//////////////////////////////////////////// CONFIG RECORD ///////////////////////////////////////////
+
+struct machine_config_method hifive_unleashed_config_method = {
+   .config_mem = query_mem,
+   .config_harts = query_soc,
+   .config_clint = query_noop,
+   .config_plic = query_plic,
+   .config_uart = query_uart,
+   .config_uart16550 = query_noop,
+   .config_htif = query_noop,
+   .config_finisher = query_noop,
+   .filter_harts = filter_harts_noop,
+   .filter_plic = query_noop,
+   .filter_compat = filter_compat_noop,
+};

machine/machine.mk.in

@@ -22,6 +22,7 @@ machine_hdrs = \
 machine_c_srcs = \
   common.c \
   configure-fdt.c \
+  configure-hifive-unleashed.c \
   mtrap.c \
   minit.c \
   htif.c \

machine/probe.h

@@ -18,6 +18,7 @@ struct machine_config_method {
 };
 
 extern struct machine_config_method fdt_config_method;
+extern struct machine_config_method hifive_unleashed_config_method;
 
 struct machine_config_method *cm;