[U-Boot] [PATCH 7/9] mx53loco: Add support to dynamically choose between ftd use or not

[Stefano Babic <sbabic@denx.de>]

On 26/12/2012 19:23, Otavio Salvador wrote:
> On Wed, Dec 26, 2012 at 10:14 AM, Fabio Estevam <festevam@gmail.com> wrote:
>> On Wed, Dec 26, 2012 at 9:31 AM, Stefano Babic <sbabic@denx.de> wrote:
>>
>>> Only to remark that this is the correct behavior. The kernel with fdt is
>>> booted independently if this is wanted or not, but if the fdt file is
>>> loaded successfully from MMC or network. This can have some drawback
>>> effects if, for example, the fdt is simply stored on the TFTP server,
>>> but we want to boot a kernel without DT. For example, when someone wants
>>> to test both kernels or there are multiple instances of the same board
>>> type (mx53loco in this case) loading from the same TFTP server.
>>>
>>> In your patch, the behavior depends if the fdt is simply present on the
>>> media, but this does not always mean that the file must be loaded.
>>> Should be not better to set variable as flag to force the desired
>>> behavior and to be sure that the system does not boot in a different way
>>> as the user thinks ?
>>>
>>> In other words, something like :
>>>
>>>         "if boot_fdt; then " \
>>>                 "if dhcp ${ftd_addr} ${ftd_file}; then " \
>>>                         "bootm ${loadaddr} - ${ftd_addr}; " \
>>>                 "else " \
>>>                         "echo Error: I cannot boot a DT kernel; \"
>>>                 "fi; \"
>>>         " else bootm; fi;\0"
>>
>>
>> Yes, I think this is a good idea and would allow us to easily switch
>> from dt to non-dt kernel during tests.
> 
> I like the idea but maybe we could have three states?
> 
> boot_fdt=yes
> 
> It'd imply force fdt and would behave as you said above;
> 
> boot_fdt=no
> 
> Would ignore the fdt completely
> 
> boot_fdt=auto
> 
> The current code, which try to load fdt and do not fail otherwise.
> 
> Comments?

Reading again your environment, it seems to me that you strictly bind
the network configuration with fdt. But they are two distinct setup.
Let's say, if I desire to start a fdt kernel but I have a static ip
address. In this case, I should load with "tftp" instead using "dhcp".
So the necessity to have a three state is due to the fact you are
setting more as one state in one shot: fdt or not, and dhcp or not. IMHO
you need two variables to manage them independently. I think I did
something like this in another board, but I do not remember which one ;-(.

So you can have:
	boot_fdt
	ip_dyn

to discriminate what the script should do.

         "if boot_fdt; then " \
		"if ip_dyn;then" \
	           "if dhcp ${ftd_addr} ${ftd_file}; then " \
        	       "bootm ${loadaddr} - ${ftd_addr}; " \
                    "else " \
                       "echo Error: I cannot boot a DT kernel; \"
		    "fi;" \
		"else tftp ${ftd_addr} ${ftd_file}
			.....

Regards,
Stefano

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