Author: wmb Date: Sat Jul 16 14:05:42 2011 New Revision: 2377 URL: http://tracker.coreboot.org/trac/openfirmware/changeset/2377
Log: Checked in linear feedback shift register code, unused at present, but related code is in cpu/arm/memtest.fth .
Added: forth/lib/lfsr.fth
Added: forth/lib/lfsr.fth ============================================================================== --- /dev/null 00:00:00 1970 (empty, because file is newly added) +++ forth/lib/lfsr.fth Sat Jul 16 14:05:42 2011 (r2377) @@ -0,0 +1,238 @@ +\ See license at end of file +purpose: Linear feedback shift register code and related memory tests + +0 value lfsr-state + +0 value lfsr-poly +: lfsr-step ( state -- state' ) + dup 2/ swap 1 and if lfsr-poly xor then +; + +[ifdef] arm-assembler +code lfsr-step ( state -- state' ) + movs tos,tos,lsr #1 + u>= if \ Carry set + set r0,`'user# lfsr-poly` + ldr r0,[up,r0] + eor tos,tos,r0 + then +c; +code lfsr-fill ( adr seed polynomial -- adr' ) + \ tos:polynomial + ldmia sp!,{r0,r1} \ r0:seed r1:adr + mov r2,r0 \ r2:lfsr + begin + str r2,[r1],#4 + movs r2,r2,lsr #1 + eorcs r2,r2,tos + cmp r2,r0 + = until + mov tos,r1 +c; +code random-fill ( adr len data index polynomial -- ) + ldmia sp!,{r1,r2,r3,r4} \ tos:poly r1:index r2:data r3:len r4:adr + + movs r3,r3,lsr #2 \ Convert to longword count + nxteq + + sub r0,r3,#1 \ r0:remaining count + + \ r3:address-lfsr r4:data-lfsr r5:data-poly + set r5,#0x80200003 \ 32-bit polynomial + + begin + \ Compute new data value with an LFSR step + movs r2,r2,lsr #1 + eorcs r2,r2,r5 + + \ Compute new address index, discarding values >= len + begin + movs r1,r1,lsr #1 + eorcs r1,r1,tos + cmp r1,r3 + u< until + + \ Write the "random" value to the "random" address (adr[index]) + str r2,[r4,r1,lsl #2] + + decs r0,#1 + 0= until + + pop tos,sp +c; +code random-check ( adr len data index remain polynomial -- false | adr len data index remain true ) + ldmia sp!,{r0,r1,r2,r3,r4} \ tos:poly r0:remain r1:index r2:data r3:len r4:adr + + cmp r0,#0 + moveq tos,#0 \ Return false + nxteq + + mov r7,r3,lsr #2 \ Convert to longword count + + set r5,#0x80200003 \ 32-bit polynomial + + begin + \ Compute new data value with an LFSR step + movs r2,r2,lsr #1 + eorcs r2,r2,r5 + + \ Compute new address index, discarding values >= len + begin + movs r1,r1,lsr #1 + eorcs r1,r1,tos + cmp r1,r7 + u< until + + \ Read the value at the "random" address (adr[index]) + ldr r6,[r4,r1,lsl #2] + + \ Compare it to the calculated value + cmp r6,r2 + + decne r0,#1 + stmnedb sp!,{r0,r1,r2,r3,r4} \ Push results + mvnne tos,#0 \ True on top of stack + nxtne + + decs r0,#1 + 0= until + + mov tos,#0 +c; +[then] +0 [if] \ This is for testing the period of various polynomials +code lfsr-period ( polynomial -- period ) + \ tos:polynomial + mov r0,#1 \ r0:seed + mov r2,r0 \ r2:lfsr + mov r1,#0 \ r1:count + begin + inc r1,#1 + movs r2,r2,lsr #1 + eorcs r2,r2,tos + cmp r2,r0 + = until + mov tos,r1 +c; +[then] +[then] +[ifdef] x86-assembler +code lfsr-step ( state -- state' ) + ax pop + 1 # ax shr + carry? if + 'user lfsr-poly bx mov + bx ax xor + then + ax push +c; +[then] + +0 [if] +\ Given a list of bit numbers for the polynomial taps, compute the mask value +\ If the polynomial is x^15 + x^14 + 1, the bit numbers are 15, 14, and 0, so +\ the argument list would be 0 14 15 . The 0 must be first to end the list. +\ The order of the others is irrelevant. +: bits>poly ( 0 bit#0 ... bit#n -- mask ) + 0 begin ( 0 bit#0 ... bit#m mask ) + over ( 0 bit# ... bit#m mask bit#m ) + while ( 0 bit#0 ... bit#m mask ) + 1 rot 1- lshift or ( 0 bit#0 ... bit#m-1 mask' ) + repeat ( 0 mask ) + nip ( mask ) +; +[then] + +\ Polynomials for maximal length LFSRs for different bit lengths +\ The values come from the Wikipedia article for Linear Feedback Shift Register and from +\ http://www.xilinx.com/support/documentation/application_notes/xapp052.pdf +create polynomials \ #bits period +h# 0 , \ 0 0 +h# 1 , \ 1 1 +h# 3 , \ 2 3 +h# 6 , \ 3 7 +h# c , \ 4 f +h# 14 , \ 5 1f +h# 30 , \ 6 3f +h# 60 , \ 7 7f +h# b8 , \ 8 ff +h# 110 , \ 9 1ff +h# 240 , \ 10 3ff +h# 500 , \ 11 7ff +h# e08 , \ 12 fff +h# 1c80 , \ 13 1fff +h# 3802 , \ 14 3fff +h# 6000 , \ 15 7fff +h# b400 , \ 16 ffff +h# 12000 , \ 17 1ffff +h# 20400 , \ 18 3ffff +h# 72000 , \ 19 7ffff +h# 90000 , \ 20 fffff +h# 140000 , \ 21 1fffff +h# 300000 , \ 22 3fffff +h# 420000 , \ 23 7fffff +h# e10000 , \ 24 ffffff +h# 1200000 , \ 25 1ffffff +h# 2000023 , \ 26 3ffffff +h# 4000013 , \ 27 7ffffff +h# 9000000 , \ 28 fffffff +h# 14000000 , \ 29 1fffffff +h# 20000029 , \ 30 3fffffff +h# 48000000 , \ 31 7fffffff +h# 80200003 , \ 32 ffffffff + +: round-up-log2 ( n -- log2 ) + dup log2 ( n log2 ) + tuck 1 swap lshift ( log2 n 2^log2 ) + > - ( log2' ) +; + +defer .lfsr-mem-error +: (.lfsr-mem-error) ( adr len data index remain -- adr len data index remain ) + push-hex + ." Error at address " 4 pick 2 pick la+ dup 8 u.r ( adr len data index remain err-adr ) + ." - expected " 3 pick 8 u.r ( adr len data index remain err-adr ) + ." got " l@ 8 u.r cr + pop-base +; +' (.lfsr-mem-error) to .lfsr-mem-error +: random-test ( adr len -- ) + dup /l <= if 2drop exit then ( adr len #bits ) + dup /l / round-up-log2 ( adr len #bits ) + polynomials swap la+ l@ ( adr len polynomial ) + + 3dup 1 1 rot random-fill ( adr len polynomial ) + + >r ( adr len r: polynomial ) + 1 1 third /l / 1- ( adr len data index remain r: polynomial ) + begin ( adr len data index remain r: polynomial ) + r@ random-check ( false | adr len data index remain true r: polynomial ) + while ( adr len data index remain r: polynomial ) + .lfsr-mem-error ( adr len data index remain r: polynomial ) + repeat ( r: polynomial ) + r> drop +; + +\ LICENSE_BEGIN +\ Copyright (c) 2010 FirmWorks +\ +\ Permission is hereby granted, free of charge, to any person obtaining +\ a copy of this software and associated documentation files (the +\ "Software"), to deal in the Software without restriction, including +\ without limitation the rights to use, copy, modify, merge, publish, +\ distribute, sublicense, and/or sell copies of the Software, and to +\ permit persons to whom the Software is furnished to do so, subject to +\ the following conditions: +\ +\ The above copyright notice and this permission notice shall be +\ included in all copies or substantial portions of the Software. +\ +\ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, +\ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF +\ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND +\ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE +\ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +\ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION +\ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. +\ +\ LICENSE_END
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