configs/qemu_sh4*: switch back to disk emulation

Back in commit
44a6b7866c95ca5459a53a50eab5ab1d38b6b8e1 ("configs/qemu_sh4*: switch
to initramfs"), the Qemu SuperH defconfigs were switched to initramfs
due to a bug in the Qemu disk emulation.

However, the initramfs solution has an issue: if the initramfs is
slightly too large (like just 6 MB!), the system no longer boots.

Since the disk emulation problem has apparently been resolved in Qemu
10 (according to testing), let's switch back to this.

In addition to essentially reverting
44a6b7866c95ca5459a53a50eab5ab1d38b6b8e1, we also need to adjust the
kernel configuration so that the kernel takes its command line for the
bootloader (in our case from the Qemu -append option). Otherwise an
hardcoded command line is used, which doesn't mount /dev/sda as the
root filesystem.

This update has been tested on Gitlab CI:

  https://gitlab.com/tpetazzoni/buildroot/-/pipelines/1968267919

Thanks to Romain Naour for pointing to the initramfs size as being the
issue.

Cc: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>

board/qemu/sh4-r2d/linux.config

@@ -5,6 +5,7 @@ CONFIG_MEMORY_START=0x0c000000
 CONFIG_FLATMEM_MANUAL=y
 CONFIG_SH_RTS7751R2D=y
 CONFIG_RTS7751R2D_PLUS=y
+CONFIG_CMDLINE_FROM_BOOTLOADER=y
 CONFIG_HEARTBEAT=y
 CONFIG_PCI=y
 CONFIG_NET=y

board/qemu/sh4-r2d/readme.txt

@@ -1,6 +1,6 @@
 Run the emulation with:
 
-  qemu-system-sh4 -M r2d -kernel output/images/zImage -append "console=ttySC1,115200 noiotrap" -serial null -serial stdio -net nic,model=rtl8139 -net user # qemu_sh4_r2d_defconfig
+  qemu-system-sh4 -M r2d -kernel output/images/zImage -drive file=output/images/rootfs.ext2,if=ide,format=raw -append "rootwait root=/dev/sda console=ttySC1,115200 noiotrap" -serial null -serial stdio -net nic,model=rtl8139 -net user # qemu_sh4_r2d_defconfig
 
 The login prompt will appear in the terminal that started Qemu.
 The graphical window is the framebuffer.

board/qemu/sh4eb-r2d/linux.config

@@ -6,6 +6,7 @@ CONFIG_FLATMEM_MANUAL=y
 CONFIG_CPU_BIG_ENDIAN=y
 CONFIG_SH_RTS7751R2D=y
 CONFIG_RTS7751R2D_PLUS=y
+CONFIG_CMDLINE_FROM_BOOTLOADER=y
 CONFIG_HEARTBEAT=y
 CONFIG_PCI=y
 CONFIG_NET=y

board/qemu/sh4eb-r2d/readme.txt

@@ -1,6 +1,6 @@
 Run the emulation with:
 
-  qemu-system-sh4eb -M r2d -kernel output/images/zImage -append "console=ttySC1,115200 noiotrap" -serial null -serial stdio -net nic,model=rtl8139 -net user # qemu_sh4eb_r2d_defconfig
+  qemu-system-sh4eb -M r2d -kernel output/images/zImage -drive file=output/images/rootfs.ext2,if=ide,format=raw -append "rootwait root=/dev/sda console=ttySC1,115200 noiotrap" -serial null -serial stdio -net nic,model=rtl8139 -net user # qemu_sh4eb_r2d_defconfig
 
 The login prompt will appear in the terminal that started Qemu.
 The graphical window is the framebuffer.

configs/qemu_sh4_r2d_defconfig

@@ -12,7 +12,7 @@ BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.12.27"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/qemu/sh4-r2d/linux.config"
 BR2_LINUX_KERNEL_ZIMAGE=y
-BR2_TARGET_ROOTFS_INITRAMFS=y
+BR2_TARGET_ROOTFS_EXT2=y
 # BR2_TARGET_ROOTFS_TAR is not set
 BR2_PACKAGE_HOST_QEMU=y
 BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y

configs/qemu_sh4eb_r2d_defconfig

@@ -12,7 +12,7 @@ BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="6.12.27"
 BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
 BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="board/qemu/sh4eb-r2d/linux.config"
 BR2_LINUX_KERNEL_ZIMAGE=y
-BR2_TARGET_ROOTFS_INITRAMFS=y
+BR2_TARGET_ROOTFS_EXT2=y
 # BR2_TARGET_ROOTFS_TAR is not set
 BR2_PACKAGE_HOST_QEMU=y
 BR2_PACKAGE_HOST_QEMU_SYSTEM_MODE=y