Re: [RFC] MPC5200 BestComm microcode [en]/[de]coding draft

Hello Sylvain, Wolfgang

Sorry for silence, I was out of office last week.
(And will be absent at next two weeks too).

Wolfgang, first question to you:
May be you are know where I could find (if it exist)
BestComm (SmartComm) API for mystic MGT5100?

Sylvain Munaut wrote:

But I'm not sure including that into the Documentation/ directory is
such a good idea. Changing documentation that's there requires sending
patch to Linus and get it processed etc ... And since It's mostly
reverse engineering, it's probably going to change often as we get a
better understanding.

I agree with Wolfgang's opinion: when I seek description of some kernel
part, I'm firstly check Documentation/, next grepping kernel tree.
In any case, when doco will be completed it will not changed often.

We could publish it as a Wiki (that's a tendency these days ;) so that
everyone can contribute easily and post code examples etc ... What do
you think ?

Agree, good think. Wolfgang, is it appropriately to use WIKI of denx.de?

See comments below for the "real" comments ;)

quoted

+[18:17]	   WS		Write Size (see above)
+[16:16]			??????????????
+[15:15]	   		Destination index prefix, 
+			if set (i.e. =1), then bitfield [13:10]
+			contain index number, and [14:14] have 
+			meaning of indirect addressing flag.
+			If this field cleared then field 
+			[14:10] contain	index of VARIABLE.
+[14:14]			Indirect addressing by idx, 
+			(and only by idx) flag, or high bit of
+			variable index.
+[13:10]			index of DESTINATION/SOURCE idx/var.
+
+[09:09]			???? For some cases 1, for another 0.????
+
+[08:08]			Same as in [14:10], but for source.
+[07:03]			Same as in [14:10], but for source.
+[02:00]	   EU3		Number of function, which will execute
+			on EU#3.

[2:0] is FN but what do you exactly mean it is. The only thing I notice
is that if it =1 then the source is "EU3()" ... whatever that means.

Also, I'm not sure it has something to do with the FDT since there is
only 3 bits.

With first 7 functions, as I understand. In theory it may be any
function (depend on functions arrangement in FDT).

quoted

+Note: For DRD1A exist special case, aka NOP, which act as 
+task terminator. Fields, in this case, have next meanings:
+
+[31:28]			Reserved must be 0.
+[27:27]	  TFD		Transfer Frame Done. 
+[26:26]	  INT 		Interrupt.
+[25:21]	  INIT		Initiator (aka requestor) number. Usually 0,
+			or ALWAYS INITIATOR.
+[16:00]	  NOP code	Must be 0x1f8 

Where did you see that that you could use theses bit in NOP ?

INT - was used in image_rtos1/TASK_PCI_TX for example.
INIT,TFD - my assumption, not sure certainly.

quoted

+Ex. Please, pay attention to first two lines: since MORE is set,
+codes for idx2 and var13 are in different fields, then for case
+where MORE is not set (var4 = var2).:
+ 0x10601010 -- DRD1A: var4 = var2; FN=0 MORE init=3 WS=0 RS=0
+ 0x00008868 -- DRD1A: idx2 = var13; FN=0 init=0 WS=0 RS=0
+ 0x0404c999 -- DRD1A: *idx2 = EU3(); FN=1 INT init=0 WS=2 RS=0
+ 0x000001f8 -- DRD1A: NOP
+ 0x040001f8 -- DRD1A: INT init=0
+
+Next two DRDs are ALWAYS coupled, i.e it is impossible to using 
+DRD2B1 without preceded DRD2A, but any (?fixme?) number DRD2B1 
+may followed by DRD2A.

? AFAIU it's either
DRD2A, DRD2B1
or
DRD2A, DRDF2B2

Oops, I miss DRD2B2, but then situation become more clean:
DRD2B2 - load accumulator of execution unit.

Then 0x1f code in DRD2B1 OP2 (and may be in OP1) mean EU accumulator.

quoted

+2) DRD2A - setup bestcomm Execution Unit (EU)
+Bitfields encodings:
+
+Bits num.  Name          Desc
+[31:31]    MORE		?????????
+[30:29]    EXT		must be always initialized 
+			by 3 (binary 11)

What I have is that
[31:29] Always 011 - Indicates a DRD2A.
[28:28] MORE -  Same meaning as before. Just tells if the following
(here that's the one that is after the corresponding DRD2B{1,2}) DRD is
in the same loop or if it's in the previous loop level ?

quoted

+[27:27]	   TFD		Transfer Frame Done.
+[26:21]	   INIT		Initiator number.
+[20:19]	   RS		Read Size 
+[18:17]	   WS		Write Size
+[16:04]			reserved, must be 0

They are the function number to use in EU#{0,1,2} but in MPC5200, only
EU3 is implemented.

I extend description.

quoted

+[03:00]	   EU3		Number of function, which will execute
+			on EU#3 at DRD2B1 time.
+Ex:
+ 0x60140002 -- DRD2A: EU3=2 EXT init=0 WS=2 RS=2
+
+3) DRD2B1 - execute function and store result of it. 

Can't find the piece if paper where I wrote about DRD2B1 ...
For DRD2B2 there is only 1 example I know of, so quite hard to deduce
anything.

Two if be more precisely :), both in CRC16 u-code.

quoted

+4) LCD - run followed loop microcode, or may be used for checking
+some conditions. LCD may be nested (only two levels are supported).

Two levels ? Didn't know that but sure there is no example with 3 levels.

Ok, I remove this sentence, it was born, because I doesn't found
how loops are terminated (as you point, it was absence of bit in
DRD :) ).

-- 
Regards
Andrey Volkov