[U-Boot] [PATCH] arm: Add support for semihosting for armv8 fastmodel targets.

[Darwin Rambo]

On 14-03-12 10:18 AM, Tom Rini wrote:
> On Wed, Mar 12, 2014 at 09:41:20AM -0700, Darwin Rambo wrote:
>>
>>
>> On 14-03-12 09:24 AM, Tom Rini wrote:
>>> On Wed, Mar 12, 2014 at 09:04:01AM -0700, Darwin Rambo wrote:
> [snip]
>>>> +	/* Assumes kernel is lower in memory than fdt */
>>>> +	smh_load(CONFIG_KNLNAME, kernel_addr, fdt_addr - kernel_addr, 1);
>>>> +
>>>> +	/* Load fdt to memory */
>>>> +	smh_load(CONFIG_FDTNAME, fdt_addr, 0x20000, 1);
>>>> +
>>>> +	/* Load initrd to memory */
>>>> +	smh_load(CONFIG_RDNAME, initrd_addr, initrd_size, 1);
>>>
>>> Is there a reason we can't also get these from the environment?  Or a
>>> limitation of (how we support) the simulator that we don't have
>>> persistent r/w environment right now?
>> These names can also come from the environment, there's r/w capability
>> there, just no physical eMMC. Thanks.
> 
> I need to play more with the foundation model then, I didn't think we
> could talk with the "mmc" or anything on it.  As you've got it coded
> now, you can't change what's loaded here :)  But if we can have a
> file-backed storage used as the "disk" and keep env there, making this
> load files named in the environment and then fw_getenv/setenv can change
> the values from Linux too, if we don't boot into a full U-Boot at some
> point.
Sorry Tom, what I really meant to say was that with fastmodel, you can
define environment variables at build and run time, but they can't be
saved or viewed as persistent for the next bootup. Semihosting is kind
of a way to get around this lack of persistence since you can load
different image files on different runs. You could even potentially load
an environment file to fake out the eMMC if warranted. By r/w
capability, I meant just for that one instance of execution of u-boot.
But you can potentially access real eMMC on palladium or FPGA for
example, and eMMC would then be persistent in that environment from run
to run. Thanks.
>