Re: [Qemu-devel] [PATCH] arm: add device tree support

[Grant Likely]

On Sun, Jan 29, 2012 at 11:15:42AM +0000, Paul Brook wrote:
> Clearly we need to have some sort of FDT support.  However I'm unconvinced 
> that it's the correct format for the primary data structure.  For one thing 
> it's a hierarchical tree structure, and in my experience describing links 
> outside that structure gets hairy.  One of the things we're doing with QOM is 
> move from a hierarchical tree/bus to a more general connected web of links 
> between devices.

Okay, well at least let's start with this.  Here is an updated version of the
patch that doesn't touch the board code.  It makes the -dtb option available
to all ARM platforms.

Even if dtb is not the primary structure, we absolutely need this option.
Developers using qemu to simulate real hardware are going to still want
to pass in the exact same .dtb file to qemu as they use for the real target,
and those .dtb files are maintained completely separately from qemu.

g.

---
diff --git a/Makefile.target b/Makefile.target
index 68481a3..5e465ec 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -363,6 +363,7 @@ obj-arm-y += vexpress.o
 obj-arm-y += strongarm.o
 obj-arm-y += collie.o
 obj-arm-y += pl041.o lm4549.o
+obj-arm-$(CONFIG_FDT) += device_tree.o
 
 obj-sh4-y = shix.o r2d.o sh7750.o sh7750_regnames.o tc58128.o
 obj-sh4-y += sh_timer.o sh_serial.o sh_intc.o sh_pci.o sm501.o
diff --git a/configure b/configure
index f69e08f..0c2deab 100755
--- a/configure
+++ b/configure
@@ -3411,6 +3411,9 @@ case "$target_arch2" in
     gdb_xml_files="arm-core.xml arm-vfp.xml arm-vfp3.xml arm-neon.xml"
     target_phys_bits=32
     target_llong_alignment=4
+    if test "$fdt" = "yes" ; then
+      target_libs_softmmu="$fdt_libs"
+    fi
   ;;
   cris)
     target_nptl="yes"
diff --git a/hw/arm_boot.c b/hw/arm_boot.c
index 5f163fd..35bfa62 100644
--- a/hw/arm_boot.c
+++ b/hw/arm_boot.c
@@ -7,11 +7,14 @@
  * This code is licensed under the GPL.
  */
 
+#include "config.h"
 #include "hw.h"
 #include "arm-misc.h"
 #include "sysemu.h"
+#include "boards.h"
 #include "loader.h"
 #include "elf.h"
+#include "device_tree.h"
 
 #define KERNEL_ARGS_ADDR 0x100
 #define KERNEL_LOAD_ADDR 0x00010000
@@ -207,6 +210,66 @@ static void set_kernel_args_old(const struct arm_boot_info 
*info,
     }
 }
 
+static int load_dtb(target_phys_addr_t addr, const struct arm_boot_info *binfo)
+{
+#ifdef CONFIG_FDT
+    uint32_t mem_reg_property[] = { cpu_to_be32(binfo->loader_start),
+                                    cpu_to_be32(binfo->ram_size) };
+    void *fdt = NULL;
+    char *filename;
+    int size, rc;
+
+    if (!current_dtb_filename)
+        return 0;
+
+    filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, current_dtb_filename);
+    if (!filename) {
+        fprintf(stderr, "Couldn't open dtb file %s\n", current_dtb_filename);
+        return -1;
+    }
+
+    fdt = load_device_tree(filename, &size);
+    if (!fdt) {
+        fprintf(stderr, "Couldn't open dtb file %s\n", filename);
+        g_free(filename);
+        return -1;
+    }
+    g_free(filename);
+
+    rc = qemu_devtree_setprop(fdt, "/memory", "reg", mem_reg_property,
+                               sizeof(mem_reg_property));
+    if (rc < 0)
+        fprintf(stderr, "couldn't set /memory/reg\n");
+
+    rc = qemu_devtree_setprop_string(fdt, "/chosen", "bootargs",
+                                      binfo->kernel_cmdline);
+    if (rc < 0)
+        fprintf(stderr, "couldn't set /chosen/bootargs\n");
+
+    if (binfo->initrd_size) {
+        rc = qemu_devtree_setprop_cell(fdt, "/chosen", "linux,initrd-start",
+                binfo->loader_start + INITRD_LOAD_ADDR);
+        if (rc < 0)
+            fprintf(stderr, "couldn't set /chosen/linux,initrd-start\n");
+
+        rc = qemu_devtree_setprop_cell(fdt, "/chosen", "linux,initrd-end",
+                    binfo->loader_start +INITRD_LOAD_ADDR +
+                    binfo->initrd_size);
+        if (rc < 0)
+            fprintf(stderr, "couldn't set /chosen/linux,initrd-end\n");
+    }
+
+    cpu_physical_memory_write (addr, fdt, size);
+
+    return 0;
+
+#else
+    fprintf(stderr, "Platform requested a device tree, "
+                "but qemu was compiled without fdt support\n");
+    return -1;
+#endif
+}
+
 static void do_cpu_reset(void *opaque)
 {
     CPUState *env = opaque;
@@ -221,12 +284,14 @@ static void do_cpu_reset(void *opaque)
         } else {
             if (env == first_cpu) {
                 env->regs[15] = info->loader_start;
-                if (old_param) {
-                    set_kernel_args_old(info, info->initrd_size,
+                if (!current_dtb_filename) {
+                    if (old_param) {
+                        set_kernel_args_old(info, info->initrd_size,
+                                            info->loader_start);
+                    } else {
+                        set_kernel_args(info, info->initrd_size,
                                         info->loader_start);
-                } else {
-                    set_kernel_args(info, info->initrd_size,
-                                    info->loader_start);
+                    }
                 }
             } else {
                 info->secondary_cpu_reset_hook(env, info);
@@ -239,10 +304,10 @@ void arm_load_kernel(CPUState *env, struct arm_boot_info 
*info)
 {
     int kernel_size;
     int initrd_size;
-    int n;
+    int n, rc;
     int is_linux = 0;
     uint64_t elf_entry;
-    target_phys_addr_t entry;
+    target_phys_addr_t entry, dtb_start;
     int big_endian;
 
     /* Load the kernel.  */
@@ -301,8 +366,22 @@ void arm_load_kernel(CPUState *env, struct arm_boot_info 
*info)
         } else {
             initrd_size = 0;
         }
+        info->initrd_size = initrd_size;
+
+        /* Place the DTB after the initrd in memory */
+        dtb_start = TARGET_PAGE_ALIGN(info->loader_start + INITRD_LOAD_ADDR +
+                                      initrd_size);
+        rc = load_dtb(dtb_start, info);
+        if (rc)
+            exit(1);
+
         bootloader[4] = info->board_id;
-        bootloader[5] = info->loader_start + KERNEL_ARGS_ADDR;
+        /* for device tree boot, we pass the DTB directly in r2. Otherwise
+         * we point to the kernel args */
+        if (current_dtb_filename)
+            bootloader[5] = dtb_start;
+        else
+            bootloader[5] = info->loader_start + KERNEL_ARGS_ADDR;
         bootloader[6] = entry;
         for (n = 0; n < sizeof(bootloader) / 4; n++) {
             bootloader[n] = tswap32(bootloader[n]);
@@ -312,7 +391,6 @@ void arm_load_kernel(CPUState *env, struct arm_boot_info 
*info)
         if (info->nb_cpus > 1) {
             info->write_secondary_boot(env, info);
         }
-        info->initrd_size = initrd_size;
     }
     info->is_linux = is_linux;
 
diff --git a/hw/boards.h b/hw/boards.h
index f6d3784..d06776c 100644
--- a/hw/boards.h
+++ b/hw/boards.h
@@ -34,5 +34,6 @@ typedef struct QEMUMachine {
 int qemu_register_machine(QEMUMachine *m);
 
 extern QEMUMachine *current_machine;
+extern const char *current_dtb_filename;
 
 #endif
diff --git a/qemu-options.hx b/qemu-options.hx
index 3a07ae8..0a01baa 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1964,6 +1964,15 @@ Use @var{file1} and @var{file2} as modules and pass 
arg=foo as parameter to the
 first module.
 ETEXI
 
+DEF("dtb", HAS_ARG, QEMU_OPTION_dtb, \
+    "-dtb file use 'file' as a device tree image\n", QEMU_ARCH_ARM)
+STEXI
address@hidden -dtb @var{file}
address@hidden -dtb
+Use @var{file} as a device tree binary (dtb) image and pass it to the kernel
+on boot.
+ETEXI
+
 STEXI
 @end table
 ETEXI
diff --git a/vl.c b/vl.c
index d88a18c..b22eae3 100644
--- a/vl.c
+++ b/vl.c
@@ -1154,6 +1154,7 @@ void pcmcia_info(Monitor *mon)
 
 static QEMUMachine *first_machine = NULL;
 QEMUMachine *current_machine = NULL;
+const char *current_dtb_filename = NULL;
 
 int qemu_register_machine(QEMUMachine *m)
 {
@@ -2304,6 +2305,9 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_initrd:
                 initrd_filename = optarg;
                 break;
+            case QEMU_OPTION_dtb:
+                current_dtb_filename = optarg;
+                break;
             case QEMU_OPTION_hda:
                 {
                     char buf[256];
@@ -3241,6 +3245,11 @@ int main(int argc, char **argv, char **envp)
         exit(1);
     }
 
+    if (!linux_boot && current_dtb_filename != NULL) {
+        fprintf(stderr, "-dtb only allowed with -kernel option\n");
+        exit(1);
+    }
+
     os_set_line_buffering();
 
     if (init_timer_alarm() < 0) {