[U-Boot-Users] LIBFDT: first version of fdt_find_compatible_node

[Wolfgang Grandegger <wg@grandegger.com>]

Hi Jerry,

 >Wolfgang Grandegger wrote:
>> Jerry Van Baren wrote:
[snip]
>> Yes, blob parsing will be done from the start of the blob until an 
>> answer is found every time a question is asked of it.  Not a paradigm of 
>> efficiency. :-/
>>
>> WRT the cached version, I have doubts about how much time it will save 
>> since I expect the "find compatible" will only be used during 
>> initialization.  Is it worth optimizing?  Really slow memory - yes. Fast 
>> memory - I doubt it.
>> a) I don't picture blobs being stored in really slow memory (no i2c 
>> memories).
>> b) If the memory really is slow, it seems like it would be as good or 
>> better to copy the blob to RAM and use it out of RAM (but there may be 
>> chicken & egg problems with that - I don't know how deeply you are 
>> looking to embed this).
>>
>> I don't know what board/processor/memory you are ultimately targeting 
>> with this, so my criticisms may not be valid.  I know denx.de 
>> support(s|ed) some very slow to boot boards that lots of tricks were 
>> done WRT optimization of env variables because they were stored in i2c 
>> memory.
> 
> I'm doing that for a MPC823 at 50 MHz, a very low-end system, and almost 
> to slow for 2.6. I will do some real measurements when time permits to 
> get a better feeling.

Here are the results of some quick measurements on my MPC855 at 80/40 
MHz with the attached code example and my DTS test file:

               from FLASH   from Memory
Non-cached:    11116 us       1703 us
Cached    :     2800 us       6226 us

Well, I think we can drop the cached version even if its 4 times faster, 
as it make life more difficult, especially in case the FDT gets updated.

Wolfgang.
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