[U-Boot-Users] Ideas on U-Boot configuration with FDT

Timur Tabi timur at freescale.com
Fri May 18 16:48:20 CEST 2007

Wolfgang Grandegger wrote:

>> I think fdt_checkboard() (or boardcheck) should be run from inside the 
>> fdt_open_into() command.  This takes advantage of the existing 
>> mechanism of fdt_open_into() to return an error.  It also allows for a 
>> device tree to be opened after U-Boot has booted.
> But it's too late for initial initialization (before RAM is available). 

Just make it so that fdt_open_into() is called early:

#if defined(CFG_FDT_ADDR_FLASH)
#if defined(CONFIG_MISC_INIT_F)
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)

and init_fdt() calls fdt_open_into().

> Using the FDT directly from ROM is not recommended because access might 
> be slow, but we likely need it for early initialization.

I don't access speed is important for the reading the FDT, especially flash vs. RAM.  It's 
not that much slower.

Timur Tabi
Linux Kernel Developer @ Freescale

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