[U-Boot] [PATCH v3] qemu-x86: Use config_distro_bootcmd

[Joshua Watt <jpewhacker@gmail.com>]

Converts qemu x86 machines to boot using distro_config. The intent is to
allow u-boot in qemu to be maximally compatible with many boot methods
without having to change the config. Previously, u-boot would only boot
in a very limited set of circumstances where there was a /boot/vmlinuz
on scsi 0:3 with no ramdisk.

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
---
 configs/qemu-x86_64_defconfig |  1 +
 configs/qemu-x86_defconfig    |  1 +
 doc/README.x86                | 17 +++++++++++++++++
 include/configs/qemu-x86.h    | 25 +++++++++++++++++++++++++
 4 files changed, 44 insertions(+)

diff --git a/configs/qemu-x86_64_defconfig b/configs/qemu-x86_64_defconfig
index d89cd44144..89118cc3dc 100644
--- a/configs/qemu-x86_64_defconfig
+++ b/configs/qemu-x86_64_defconfig
@@ -12,6 +12,7 @@ CONFIG_SMP=y
 CONFIG_GENERATE_PIRQ_TABLE=y
 CONFIG_GENERATE_MP_TABLE=y
 CONFIG_GENERATE_ACPI_TABLE=y
+CONFIG_DISTRO_DEFAULTS=y
 CONFIG_BUILD_ROM=y
 CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT=y
diff --git a/configs/qemu-x86_defconfig b/configs/qemu-x86_defconfig
index 898d656ac3..a50285beec 100644
--- a/configs/qemu-x86_defconfig
+++ b/configs/qemu-x86_defconfig
@@ -6,6 +6,7 @@ CONFIG_SMP=y
 CONFIG_GENERATE_PIRQ_TABLE=y
 CONFIG_GENERATE_MP_TABLE=y
 CONFIG_GENERATE_ACPI_TABLE=y
+CONFIG_DISTRO_DEFAULTS=y
 CONFIG_BUILD_ROM=y
 CONFIG_FIT=y
 CONFIG_BOOTSTAGE=y
diff --git a/doc/README.x86 b/doc/README.x86
index 8e0a3f36ed..a00ae69acc 100644
--- a/doc/README.x86
+++ b/doc/README.x86
@@ -466,6 +466,23 @@ If you want to check both consoles, use '-serial stdio'.
 Multicore is also supported by QEMU via '-smp n' where n is the number of cores
 to instantiate. Note, the maximum supported CPU number in QEMU is 255.
 
+U-Boot uses 'distro_bootcmd' by default when booting on x86 QEMU. This tries to
+load a boot script, kernel, and ramdisk from several different interfaces. For
+the default boot order, see 'qemu-x86.h'. For more information, see
+'README.distro'. Most Linux distros can be booted by writing a uboot script.
+For example, Debian (stretch) can be booted by creating a script file named
+'boot.txt' with the contents:
+
+ setenv bootargs root=/dev/sda1 ro
+ load ${devtype} ${devnum}:${distro_bootpart} ${kernel_addr_r} /vmlinuz
+ load ${devtype} ${devnum}:${distro_bootpart} ${ramdisk_addr_r} /initrd.img
+ zboot ${kernel_addr_r} - ${ramdisk_addr_r} ${filesize}
+
+Then compile and install it with:
+
+ $ apt install u-boot-tools && \
+     mkimage -T script -C none -n "Boot script" -d boot.txt /boot/boot.scr
+
 The fw_cfg interface in QEMU also provides information about kernel data,
 initrd, command-line arguments and more. U-Boot supports directly accessing
 these informtion from fw_cfg interface, which saves the time of loading them
diff --git a/include/configs/qemu-x86.h b/include/configs/qemu-x86.h
index 64e7a60b8a..097ed414f8 100644
--- a/include/configs/qemu-x86.h
+++ b/include/configs/qemu-x86.h
@@ -10,8 +10,33 @@
 #ifndef __CONFIG_H
 #define __CONFIG_H
 
+#include <linux/sizes.h>
+
+#define BOOT_TARGET_DEVICES(func) \
+	func(USB, usb, 0) \
+	func(SCSI, scsi, 0) \
+	func(VIRTIO, virtio, 0) \
+	func(IDE, ide, 0) \
+	func(DHCP, dhcp, na)
+
+#include <config_distro_bootcmd.h>
 #include <configs/x86-common.h>
 
+#undef CONFIG_ENV_SIZE
+#define CONFIG_ENV_SIZE			SZ_256K
+
+#define CONFIG_PREBOOT "pci enum"
+
+#undef CONFIG_EXTRA_ENV_SETTINGS
+#define CONFIG_EXTRA_ENV_SETTINGS \
+	CONFIG_STD_DEVICES_SETTINGS \
+	"scriptaddr=0x7000000\0" \
+	"kernel_addr_r=0x1000000\0" \
+	"ramdisk_addr_r=0x4000000\0" \
+	"consoledev=ttyS0\0" \
+	CONFIG_OTHBOOTARGS \
+	BOOTENV
+
 #define CONFIG_SYS_MONITOR_LEN		(1 << 20)
 
 #define CONFIG_STD_DEVICES_SETTINGS	"stdin=serial,i8042-kbd\0" \
-- 
2.21.0