Re: [PATCH v5 01/11] hw: arm: Add bananapi M2-Ultra and allwinner-r40 support

[Guenter Roeck]

Hi,

On Tue, May 23, 2023 at 06:04:58PM +0800, qianfanguijin@163.com wrote:
> From: qianfan Zhao <qianfanguijin@163.com>
> 
> Allwinner R40 (sun8i) SoC features a Quad-Core Cortex-A7 ARM CPU,
> and a Mali400 MP2 GPU from ARM. It's also known as the Allwinner T3
> for In-Car Entertainment usage, A40i and A40pro are variants that
> differ in applicable temperatures range (industrial and military).
> 
> Signed-off-by: qianfan Zhao <qianfanguijin@163.com>
> Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>

I tried this in mainline linux with the following command.

qemu-system-arm -M bpim2u \
        -kernel arch/arm/boot/zImage -no-reboot \
        -snapshot -drive file=rootfs-armv7a.ext2,format=raw,if=sd \
        -nic user \
        --append "root=/dev/mmcblk0 rootwait console=ttyS0,115200" \
        -dtb arch/arm/boot/dts/sun8i-r40-bananapi-m2-ultra.dtb \
        -nographic -monitor null -serial stdio

Main problem is that the SD card gets instantiated randomly to
mmc0, mmc1, or mmc2, making it all but impossible to specify a
root file system device. The non-instantiated cards are always
reported as non-removable, including mmc0. Example:

mmc0: Failed to initialize a non-removable card

Using "-sd <file>" instead of "-drive file=<file>" does not
make a difference.

I can fix (work around ?) the problem by adding the following information
to the devicetree file.

        aliases {
                ethernet0 = &gmac;
                serial0 = &uart0;
+               mmc0 = &mmc0;
+               mmc1 = &mmc1;
+               mmc2 = &mmc2;
        };

Linux upstream commits fa2d0aa96941 and 2a43322ca7f3 describe the
logic behind this change.

Is this a bug in the Linux kernel, or a problem with the qemu emulation ?
Either case, is there a way to specify a qemu command line that doesn't
result in random assignments of the provided drive to mmc0/1/2 ?

Thanks,
Guenter