[PATCH v2 3/6] hw/riscv: Make FDT optional for MPFS

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

Real-time kernels such as RTEMS or Zephyr may use a static device tree
built into the kernel image.  Do not require to use the -dtb option if
-kernel is used for the microchip-icicle-kit machine.  Issue a warning
if no device tree is provided by the user since the machine does not
generate one.

Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de>
---
 hw/riscv/microchip_pfsoc.c | 56 +++++++++++++++++++-------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/hw/riscv/microchip_pfsoc.c b/hw/riscv/microchip_pfsoc.c
index f477d2791e..844dc0545c 100644
--- a/hw/riscv/microchip_pfsoc.c
+++ b/hw/riscv/microchip_pfsoc.c
@@ -516,7 +516,6 @@ static void microchip_icicle_kit_machine_init(MachineState *machine)
     uint64_t mem_low_size, mem_high_size;
     hwaddr firmware_load_addr;
     const char *firmware_name;
-    bool kernel_as_payload = false;
     target_ulong firmware_end_addr, kernel_start_addr;
     uint64_t kernel_entry;
     uint64_t fdt_load_addr;
@@ -589,25 +588,12 @@ static void microchip_icicle_kit_machine_init(MachineState *machine)
      *
      * This ensures backwards compatibility with how we used to expose -bios
      * to users but allows them to run through direct kernel booting as well.
-     *
-     * When -kernel is used for direct boot, -dtb must be present to provide
-     * a valid device tree for the board, as we don't generate device tree.
      */
 
-    if (machine->kernel_filename && machine->dtb) {
-        int fdt_size;
-        machine->fdt = load_device_tree(machine->dtb, &fdt_size);
-        if (!machine->fdt) {
-            error_report("load_device_tree() failed");
-            exit(1);
-        }
-
+    if (machine->kernel_filename) {
         firmware_name = RISCV64_BIOS_BIN;
         firmware_load_addr = memmap[MICROCHIP_PFSOC_DRAM_LO].base;
-        kernel_as_payload = true;
-    }
-
-    if (!kernel_as_payload) {
+    } else {
         firmware_name = BIOS_FILENAME;
         firmware_load_addr = RESET_VECTOR;
     }
@@ -617,7 +603,7 @@ static void microchip_icicle_kit_machine_init(MachineState *machine)
                                                      &firmware_load_addr, NULL);
 
     riscv_boot_info_init(&boot_info, &s->soc.u_cpus);
-    if (kernel_as_payload) {
+    if (machine->kernel_filename) {
         kernel_start_addr = riscv_calc_kernel_start_addr(&boot_info,
                                                          firmware_end_addr);
 
@@ -625,19 +611,33 @@ static void microchip_icicle_kit_machine_init(MachineState *machine)
                           true, NULL);
         kernel_entry = boot_info.image_low_addr;
 
-        /* Compute the fdt load address in dram */
-        hwaddr kernel_ram_base = memmap[MICROCHIP_PFSOC_DRAM_LO].base;
-        hwaddr kernel_ram_size = memmap[MICROCHIP_PFSOC_DRAM_LO].size;
-
-        if (kernel_entry - kernel_ram_base >= kernel_ram_size) {
-            kernel_ram_base = memmap[MICROCHIP_PFSOC_DRAM_HI].base;
-            kernel_ram_size = mem_high_size;
+        if (machine->dtb) {
+            int fdt_size;
+            machine->fdt = load_device_tree(machine->dtb, &fdt_size);
+            if (!machine->fdt) {
+                error_report("load_device_tree() failed");
+                exit(1);
+            }
+
+            /* Compute the FDT load address in DRAM */
+            hwaddr kernel_ram_base = memmap[MICROCHIP_PFSOC_DRAM_LO].base;
+            hwaddr kernel_ram_size = memmap[MICROCHIP_PFSOC_DRAM_LO].size;
+
+            if (kernel_entry - kernel_ram_base >= kernel_ram_size) {
+                kernel_ram_base = memmap[MICROCHIP_PFSOC_DRAM_HI].base;
+                kernel_ram_size = mem_high_size;
+            }
+
+            fdt_load_addr = riscv_compute_fdt_addr(kernel_ram_base, kernel_ram_size,
+                                                   machine, &boot_info);
+            riscv_load_fdt(fdt_load_addr, machine->fdt);
+        } else {
+            warn_report_once("The QEMU microchip-icicle-kit machine does not "
+                             "generate a device tree, so no device tree is "
+                             "being provided to the guest.");
+            fdt_load_addr = 0;
         }
 
-        fdt_load_addr = riscv_compute_fdt_addr(kernel_ram_base, kernel_ram_size,
-                                               machine, &boot_info);
-        riscv_load_fdt(fdt_load_addr, machine->fdt);
-
         /* Load the reset vector */
         riscv_setup_rom_reset_vec(machine, &s->soc.u_cpus, firmware_load_addr,
                                   memmap[MICROCHIP_PFSOC_ENVM_DATA].base,
-- 
2.43.0