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################################################################################
# memtest.s -- Test external RAM memory (XRAM)
#-------------------------------------------------------------------------------
# This program tests the external RAM (connected to the core through the cache
# module). Currently it only finds the RAM top address if given the bottom
# address. Subsequent versions will add some minimal diagnostic capability,
# which will be needed when DRAM access is implemented.
#
# This program does only support a single continuous chunk of RAM. If the cache
# module ever supports more than one chunk (e.g. DRAM and SRAM as in the DE-1
# board) this program will be modified accordingly.
#
# The program assumes there's no useable r/w memory other than the XRAM so it
# does not use any memory for variables or stack.
#
#-------------------------------------------------------------------------------
# To be run from reset vector, standalone. Interrupts must be disabled.
#
################################################################################
 
    #---- Set to >0 to enable a few debug messages
    .set DEBUG,         0
 
    #----
    #.set XRAM_BASE,     0x80000000          # 1st XRAM address
    .set XRAM_MAX,      1024                # max. no. of KB to test for
 
    .set UART_BASE,     0x20000000          # UART base address
    .set UART_TX,       0x0000              # TX reg offset
    .set UART_STATUS,   0x0020              # status reg offset
 
    #---------------------------------------------------------------------------
 
    .text
    .align  2
    .globl  entry
    .ent    entry
entry:
    .set    noreorder
 
    b       start_test
    nop
 
    .ifgt   0
    #--- Trap handler address: we don't expect any traps -----------------------
    #.org    0x3c
    .org    0x0180
interrupt_vector:
    b       interrupt_vector
    nop
    .endif
 
#-------------------------------------------------------------------------------
 
start_test:
    mtc0    $0,$12              # disable interrupts
 
    la      $a0,msg0
    jal     puts
    nop
    li      $a0,XRAM_BASE
    li      $a1,8
    jal     put_hex
    nop
    la      $a0,crlf
    jal     puts
    nop
 
    la      $t0,XRAM_BASE+4     # address of memory word being tested
    li      $t2,XRAM_MAX        # max amount of KBs to test for
    li      $t3,1               # (used to decrement $t2)
    li      $t4,0               # no. of KBs found
    move    $t5,$t0             # keep the start addr at hand for comparison
 
    sw      $zero,0($t0)        # clear 1st test word (in case of prev. run)
 
test_loop:
    lw      $t1,0($t0)          # read word contents
    beq     $t5,$t1,hit_mirror  # if it's the start address, we hit a mirror
    nop                         # we rolled off the end of the RAM back here
    sw      $t0,0($t0)          # word = word address
    lw      $t1,0($t0)          # read word back...
    bne     $t1,$t0,bad_word    # ...and if no match, we run off the RAM
    nop                         #
    sub     $t2,$t2,$t3         # decrement loop counter...
    bnez    $t2,test_loop       # ...and go back if there's more to go
    addiu   $t0,0x400           # in any case, increment test address by 1KB
 
    b       end_test            # end of memory found, result is in $t4
    nop
 
hit_mirror:                     # memory mirror detected
    .ifgt   DEBUG
    la      $a0,msg_mirror
    jal     puts
    nop
    .endif
    b       end_test
    nop
 
bad_word:                       # readback error detected (maybe r/o area?)
    .ifgt   DEBUG
    la      $a0,msg_bad
    jal     puts
    nop
    .endif
    b       end_test
    nop
 
end_test:                       # test done, ramtop+4 in $t0, #KB in $t4
 
 
    la      $a0,msg1            # Print ramtop message...
    jal     puts
    nop
    addi    $a0,$t0,-4          # substract the +4 offset we added before
    move    $sp,$t0             # init SP at the top of RAM space
    addi    $sp,$sp,-4
    li      $a1,8
    jal     put_hex
    nop
    la      $a0,crlf
    jal     puts
    nop
 
    # FIXME now we should so some strong test on the RAM to see if it's wired
    # correctly, using the right timing, etc.
 
    # Ok, now we know we have some RAM and stack space we can do some further
    # testing.
    # dump the first few words of FLASH
 
    la      $a0,msg2
    jal     puts
    nop
 
    # FIXME flash base address is hardcoded
    li      $a0,0xb0000000
    jal     put_hex
    ori     $a1,$zero,8
 
    la      $a0,crlf
    jal     puts
    nop
 
    la      $a0,crlf
    jal     puts
    nop
 
    li      $a0,0xb0000000
    jal     dump_hex
    ori     $a1,$zero,24
 
 
$DONE:
    j       $DONE               # ...and freeze here
    nop
 
 
#---- Functions ----------------------------------------------------------------
 
# void dump_hex(int *address, int len)
dump_hex:
    move    $t7,$a0
    move    $t8,$a1
    sw      $ra,0($sp)
    addi    $sp,$sp,-4
 
dump_hex_loop:
    lw      $a0,0($t7)
    jal     put_hex
    li      $a1,8
 
    la      $a0,space
    jal     puts
    addi    $t7,4
 
    addi    $t8,$t8,-1
    bnez    $t8,dump_hex_loop
    nop
 
    lw      $ra,4($sp)
    jr      $ra
    addi    $sp,$sp,4
 
 
#--- Special functions that do not use any RAM ---------------------------------
# WARNING: Not for general use!
# All parameters in $a0..$a4, stack unused. No attempt to comply with any ABI
# has been made.
# Since we can't use any RAM, register have been used liberally with no regard
# for intended usage -- have to share reg bank with calling function.
 
# void puts(char *s) -- print zero-terminated string
puts:
    la      $a2,UART_BASE       # UART base address
puts_loop:
    lb      $v0,0($a0)
    beqz    $v0,puts_end
    addiu   $a0,1
puts_wait_tx_rdy:
    lw      $v1,UART_STATUS($a2)
    andi    $v1,$v1,0x02
    beqz    $v1,puts_wait_tx_rdy
    nop
    sw      $v0,UART_TX($a2)
    b       puts_loop
    nop
 
puts_end:
    jr      $ra
    nop
 
# void put_hex(int n, int d) -- print integer as d-digit hex
put_hex:
    la      $a2,UART_BASE
    la      $a3,put_hex_table
    addi    $a1,-1
    add     $a1,$a1,$a1
    add     $a1,$a1,$a1
 
put_hex_loop:
    srlv    $v0,$a0,$a1
    andi    $v0,$v0,0x0f
    addu    $s2,$a3,$v0
    lb      $v0,0($s2)
put_hex_wait_tx_rdy:
    lw      $v1,UART_STATUS($a2)
    andi    $v1,$v1,0x02
    beqz    $v1,put_hex_wait_tx_rdy
    nop
    sw      $v0,UART_TX($a2)
 
    bnez    $a1,put_hex_loop
    addi    $a1,-4
 
    jr      $ra
    nop
 
 
#---- Constant data (note we keep it in the text section) ----------------------
 
put_hex_table:
    .ascii  "0123456789abcdef"
 
msg0:
    .ascii  "\n\r"
    .asciz  "Scanning external memory at 0x"
msg1:
    .asciz  "Found XRAM top at           0x"
crlf:
    .asciz "\n\r"
space:
    .asciz "  "
msg_mirror:
    .asciz "hit mirror!\n\r"
msg_bad:
    .asciz "bad readback!\n\r"
msg2:
    .asciz "\n\rDumping the first few words of FLASH at address 0x"
 
    .set    reorder
    .end    entry
 

Line No.	Rev	Author	Line
1	50	ja_rd	`################################################################################`
2			`# memtest.s -- Test external RAM memory (XRAM)`
3			`#-------------------------------------------------------------------------------`
4			`# This program tests the external RAM (connected to the core through the cache`
5			`# module). Currently it only finds the RAM top address if given the bottom`
6			`# address. Subsequent versions will add some minimal diagnostic capability,`
7			`# which will be needed when DRAM access is implemented.`
8			`#`
9			`# This program does only support a single continuous chunk of RAM. If the cache`
10			`# module ever supports more than one chunk (e.g. DRAM and SRAM as in the DE-1`
11			`# board) this program will be modified accordingly.`
12			`#`
13			`# The program assumes there's no useable r/w memory other than the XRAM so it`
14			`# does not use any memory for variables or stack.`
15			`#`
16			`#-------------------------------------------------------------------------------`
17			`# To be run from reset vector, standalone. Interrupts must be disabled.`
18			`#`
19			`################################################################################`
20
21			`#---- Set to >0 to enable a few debug messages`
22			`.set DEBUG, 0`
23
24			`#----`
25	66	ja_rd	`#.set XRAM_BASE, 0x80000000 # 1st XRAM address`
26	50	ja_rd	`.set XRAM_MAX, 1024 # max. no. of KB to test for`
27
28			`.set UART_BASE, 0x20000000 # UART base address`
29			`.set UART_TX, 0x0000 # TX reg offset`
30			`.set UART_STATUS, 0x0020 # status reg offset`
31
32			`#---------------------------------------------------------------------------`
33
34			`.text`
35			`.align 2`
36			`.globl entry`
37			`.ent entry`
38			`entry:`
39			`.set noreorder`
40
41			`b start_test`
42			`nop`
43
44	66	ja_rd	`.ifgt 0`
45	50	ja_rd	`#--- Trap handler address: we don't expect any traps -----------------------`
46	66	ja_rd	`#.org 0x3c`
47			`.org 0x0180`
48	50	ja_rd	`interrupt_vector:`
49			`b interrupt_vector`
50			`nop`
51	66	ja_rd	`.endif`
52
53	50	ja_rd	`#-------------------------------------------------------------------------------`
54
55			`start_test:`
56			`mtc0 $0,$12 # disable interrupts`
57
58			`la $a0,msg0`
59			`jal puts`
60			`nop`
61			`li $a0,XRAM_BASE`
62			`li $a1,8`
63			`jal put_hex`
64			`nop`
65			`la $a0,crlf`
66			`jal puts`
67			`nop`
68
69	66	ja_rd	`la $t0,XRAM_BASE+4 # address of memory word being tested`
70	50	ja_rd	`li $t2,XRAM_MAX # max amount of KBs to test for`
71			`li $t3,1 # (used to decrement $t2)`
72			`li $t4,0 # no. of KBs found`
73			`move $t5,$t0 # keep the start addr at hand for comparison`
74
75			`sw $zero,0($t0) # clear 1st test word (in case of prev. run)`
76
77			`test_loop:`
78			`lw $t1,0($t0) # read word contents`
79			`beq $t5,$t1,hit_mirror # if it's the start address, we hit a mirror`
80			`nop # we rolled off the end of the RAM back here`
81			`sw $t0,0($t0) # word = word address`
82			`lw $t1,0($t0) # read word back...`
83			`bne $t1,$t0,bad_word # ...and if no match, we run off the RAM`
84			`nop #`
85			`sub $t2,$t2,$t3 # decrement loop counter...`
86			`bnez $t2,test_loop # ...and go back if there's more to go`
87			`addiu $t0,0x400 # in any case, increment test address by 1KB`
88
89			`b end_test # end of memory found, result is in $t4`
90			`nop`
91
92			`hit_mirror: # memory mirror detected`
93			`.ifgt DEBUG`
94			`la $a0,msg_mirror`
95			`jal puts`
96			`nop`
97			`.endif`
98			`b end_test`
99			`nop`
100
101			`bad_word: # readback error detected (maybe r/o area?)`
102			`.ifgt DEBUG`
103			`la $a0,msg_bad`
104			`jal puts`
105			`nop`
106			`.endif`
107			`b end_test`
108			`nop`
109
110	78	ja_rd	`end_test: # test done, ramtop+4 in $t0, #KB in $t4`
111
112
113	50	ja_rd	`la $a0,msg1 # Print ramtop message...`
114			`jal puts`
115			`nop`
116	66	ja_rd	`addi $a0,$t0,-4 # substract the +4 offset we added before`
117	78	ja_rd	`move $sp,$t0 # init SP at the top of RAM space`
118			`addi $sp,$sp,-4`
119	50	ja_rd	`li $a1,8`
120			`jal put_hex`
121			`nop`
122			`la $a0,crlf`
123			`jal puts`
124			`nop`
125
126	78	ja_rd	`# FIXME now we should so some strong test on the RAM to see if it's wired`
127			`# correctly, using the right timing, etc.`
128
129			`# Ok, now we know we have some RAM and stack space we can do some further`
130			`# testing.`
131			`# dump the first few words of FLASH`
132
133			`la $a0,msg2`
134			`jal puts`
135			`nop`
136
137			`# FIXME flash base address is hardcoded`
138			`li $a0,0xb0000000`
139			`jal put_hex`
140			`ori $a1,$zero,8`
141
142			`la $a0,crlf`
143			`jal puts`
144			`nop`
145
146			`la $a0,crlf`
147			`jal puts`
148			`nop`
149
150			`li $a0,0xb0000000`
151			`jal dump_hex`
152			`ori $a1,$zero,24`
153
154
155	50	ja_rd	`$DONE:`
156			`j $DONE # ...and freeze here`
157			`nop`
158
159
160			`#---- Functions ----------------------------------------------------------------`
161	78	ja_rd
162			`# void dump_hex(int *address, int len)`
163			`dump_hex:`
164			`move $t7,$a0`
165			`move $t8,$a1`
166			`sw $ra,0($sp)`
167			`addi $sp,$sp,-4`
168
169			`dump_hex_loop:`
170			`lw $a0,0($t7)`
171			`jal put_hex`
172			`li $a1,8`
173
174			`la $a0,space`
175			`jal puts`
176			`addi $t7,4`
177
178			`addi $t8,$t8,-1`
179			`bnez $t8,dump_hex_loop`
180			`nop`
181
182			`lw $ra,4($sp)`
183			`jr $ra`
184			`addi $sp,$sp,4`
185
186
187			`#--- Special functions that do not use any RAM ---------------------------------`
188	50	ja_rd	`# WARNING: Not for general use!`
189			`# All parameters in $a0..$a4, stack unused. No attempt to comply with any ABI`
190			`# has been made.`
191			`# Since we can't use any RAM, register have been used liberally with no regard`
192			`# for intended usage -- have to share reg bank with calling function.`
193
194			`# void puts(char *s) -- print zero-terminated string`
195			`puts:`
196	78	ja_rd	`la $a2,UART_BASE # UART base address`
197	50	ja_rd	`puts_loop:`
198			`lb $v0,0($a0)`
199			`beqz $v0,puts_end`
200			`addiu $a0,1`
201			`puts_wait_tx_rdy:`
202	78	ja_rd	`lw $v1,UART_STATUS($a2)`
203	50	ja_rd	`andi $v1,$v1,0x02`
204			`beqz $v1,puts_wait_tx_rdy`
205			`nop`
206	78	ja_rd	`sw $v0,UART_TX($a2)`
207	50	ja_rd	`b puts_loop`
208			`nop`
209
210			`puts_end:`
211			`jr $ra`
212			`nop`
213
214			`# void put_hex(int n, int d) -- print integer as d-digit hex`
215			`put_hex:`
216	78	ja_rd	`la $a2,UART_BASE`
217			`la $a3,put_hex_table`
218	50	ja_rd	`addi $a1,-1`
219			`add $a1,$a1,$a1`
220			`add $a1,$a1,$a1`
221
222			`put_hex_loop:`
223			`srlv $v0,$a0,$a1`
224			`andi $v0,$v0,0x0f`
225	78	ja_rd	`addu $s2,$a3,$v0`
226	50	ja_rd	`lb $v0,0($s2)`
227			`put_hex_wait_tx_rdy:`
228	78	ja_rd	`lw $v1,UART_STATUS($a2)`
229	50	ja_rd	`andi $v1,$v1,0x02`
230			`beqz $v1,put_hex_wait_tx_rdy`
231			`nop`
232	78	ja_rd	`sw $v0,UART_TX($a2)`
233	50	ja_rd
234			`bnez $a1,put_hex_loop`
235			`addi $a1,-4`
236
237			`jr $ra`
238			`nop`
239
240
241			`#---- Constant data (note we keep it in the text section) ----------------------`
242
243			`put_hex_table:`
244			`.ascii "0123456789abcdef"`
245
246			`msg0:`
247			`.ascii "\n\r"`
248			`.asciz "Scanning external memory at 0x"`
249			`msg1:`
250			`.asciz "Found XRAM top at 0x"`
251			`crlf:`
252			`.asciz "\n\r"`
253			`space:`
254			`.asciz " "`
255			`msg_mirror:`
256			`.asciz "hit mirror!\n\r"`
257			`msg_bad:`
258			`.asciz "bad readback!\n\r"`
259	78	ja_rd	`msg2:`
260			`.asciz "\n\rDumping the first few words of FLASH at address 0x"`
261	50	ja_rd
262			`.set reorder`
263			`.end entry`
264

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