[meta-xilinx] Kernel Command Line problem

[Mike Looijmans]

My experience so far has been that the u-boot provided commandline prevails 
over the one in the devicetree. I also use the commandline to switch between 
rootfs locations (e.g. SD or internal flash via UBI) and have never 
encountered any problems. In my case, the devicetree sets up rootfs in flash, 
while the commandline will override this to boot from SD card.

I think you should check the kernel configuration, there are configuration 
items that allow overriding this behavior.

In addition, check that u-boot is properly passing the commandline along, 
maybe the kernel isn't getting what it expects.

Mike.

On 12/04/2013 03:57 PM, Martin Townsend wrote:
> Hi,
>
> I now have the 3.10 Kernel booting.  I had an issue where my Kernel bootargs
> that I had setup in the U-Boot environment weren't being used by the Kernel.
> After some debugging I found that they were being overwritten by the ones in
> the 'chosen' section of the device tree.  My understanding (which may be
> wrong) is that the bootargs passed by the bootloader have a higher precedence
> than the one in the device tree so I hacked the prom.c file in
> arch/microblaze/kernel/prom.c so it doesn't process 'chosen' to get things
> working.  The reason I want to use U-Boot bootargs is that we are mounting the
> Root Filesystem using NFS and each board will have a different rootpath
> variable in the U-Boot env, we are also storing the unique MAC address here
> too.  It's easier to program a unique environment rather than regenerate the
> device tree.
>
> First am I right in assuming the bootloader should have higher precedence and
> if so I would appreciate if someone could look at this patch that I'm using as
> a hack and advise on the right way to do it :)
>
> Best Regards,
> Martin.
>
> diff --git a/arch/microblaze/kernel/prom.c b/arch/microblaze/kernel/prom.c
> index 0a2c68f..bff2c75 100644
> --- a/arch/microblaze/kernel/prom.c
> +++ b/arch/microblaze/kernel/prom.c
> @@ -118,7 +118,8 @@ void __init early_init_devtree(void *params)
>        * device-tree, including the platform type, initrd location and
>        * size, TCE reserve, and more ...
>        */
> -    of_scan_flat_dt(early_init_dt_scan_chosen, cmd_line);
> +    if(cmd_line[0] == '\0')
> +        of_scan_flat_dt(early_init_dt_scan_chosen, cmd_line);
>
>       /* Scan memory nodes and rebuild MEMBLOCKs */
>       of_scan_flat_dt(early_init_dt_scan_root, NULL);