mailbox: Writes dissapear #37

olajep · 2016-01-19T19:27:41Z

I need to insert nops between writes to the mailbox from Epiphany.

aolofsson · 2016-01-19T20:37:22Z

Can you try the following:
-run two scenarios, one with 0 noops inserted and one with 16 nops inserted
-for each scenario, try twoo addresses, 1.) write to mailboxlo, 2) write to
some address in memory

what do you get?

On Tue, Jan 19, 2016 at 2:27 PM, Ola Jeppsson notifications@github.com
wrote:

I need to insert nops between writes to the mailbox from Epiphany.

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#37.

Andreas Olofsson, CEO/Founder at Adapteva
Cell: +1 781 325 6688
Twitter: @adapteva
Web: adapteva.com

Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

olajep · 2016-01-19T20:57:22Z

Do you want:

Write to mailbox
Write to DRAM
nops / no nops

or

Write to mailbox
nops / no nops
Write to DRAM
nops / no nops

// Ola

aolofsson · 2016-01-19T21:11:00Z

I want to see what happens with the exact same Epiphany code with the only
difference being the addressing being written to. My theory is that you
happened on a corner case that affects all writes from Epiphany to FPGA.
The reason we may not have see this is that you wrote a tight assembly
loop. Our other tests either use DMA (streaming) or slow C code loops. (in
other words our elink test regression still needs major work!) Would ftest,
matmul, etc code have the same sequence that you wrote in assembly for
mailbox test?

(a fix has tested and checked in)

On Tue, Jan 19, 2016 at 3:57 PM, Ola Jeppsson notifications@github.com
wrote:

Do you want:

Write to mailbox

Write to DRAM

nops / no nops

or

Write to mailbox

nops / no nops

Write to DRAM

nops / no nops

// Ola

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#37 (comment).

Andreas Olofsson, CEO/Founder at Adapteva
Cell: +1 781 325 6688
Twitter: @adapteva
Web: adapteva.com

Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

olajep · 2016-01-19T21:14:43Z

Without nops but with an added str to 0x8f100000 all ten writes to the mailbox arrives. The ARM side reads until E_MAILBOXSTATUS == 0.

00000660 <_main>:
 660:   4a0b 0552       mov r2,0x5550
 664:   754b 0aa2       mov r3,0xaaaa
 668:   060b 4072       mov r16,0x730
 66c:   4aab 1552       movt r2,0x5555
 670:   754b 1aa2       movt r3,0xaaaa
 674:   01eb 5812       movt r16,0x810f
 678:   200b 0002       mov r1,0x0
 67c:   800b 2502       mov r12,0x5000
 680:   407c 0800       strd r2,[r16]
 684:   220b 18f2       movt r1,0x8f10
 688:   954b 3aa2       movt r12,0xaaaa
 68c:   845c 2000       str r12,[r1]
 690:   407c 0800       strd r2,[r16]
 694:   845c 2000       str r12,[r1]
 698:   407c 0800       strd r2,[r16]
 69c:   845c 2000       str r12,[r1]
 6a0:   407c 0800       strd r2,[r16]
 6a4:   845c 2000       str r12,[r1]
 6a8:   407c 0800       strd r2,[r16]
 6ac:   845c 2000       str r12,[r1]
 6b0:   407c 0800       strd r2,[r16]
 6b4:   845c 2000       str r12,[r1]
 6b8:   407c 0800       strd r2,[r16]
 6bc:   845c 2000       str r12,[r1]
 6c0:   407c 0800       strd r2,[r16]
 6c4:   845c 2000       str r12,[r1]
 6c8:   407c 0800       strd r2,[r16]
 6cc:   845c 2000       str r12,[r1]
 6d0:   407c 0800       strd r2,[r16]
 6d4:   845c 2000       str r12,[r1]
 6d8:   194f 0402       rts
 6dc:   0000            beq 6dc <_main+0x7c>
        ...

EDIT: With commit
b26255d

olajep · 2016-01-19T21:35:23Z

Bug is still present in e865672
Running through epiphany examples now ...

olajep · 2016-01-19T21:53:56Z

(examples still work)

The magic number with e865672 is 10 cycles (no stalls AFAIK) between each strd

I.e., this works:

00000660 <_main>:
 660:   0a0b 0552       mov r0,0x5550
 664:   354b 0aa2       mov r1,0xaaaa
 668:   460b 0072       mov r2,0x730
 66c:   0aab 1552       movt r0,0x5555
 670:   354b 1aa2       movt r1,0xaaaa
 674:   41eb 1812       movt r2,0x810f
 678:   0874            strd r0,[r2]
 67a:   01a2            nop
 67c:   01a2            nop
 67e:   01a2            nop
 680:   01a2            nop
 682:   01a2            nop
 684:   01a2            nop
 686:   0a0b 0552       mov r0,0x5550
 68a:   354b 0aa2       mov r1,0xaaaa
 68e:   0aab 1552       movt r0,0x5555
 692:   354b 1aa2       movt r1,0xaaaa
 696:   0874            strd r0,[r2]
 698:   01a2            nop
...

Remove one nop and things break (only 6 entries in fifo)

olajep · 2016-01-19T22:00:36Z

@aolofsson

Which are the right values for ELINK_RXDELAY0 and ELINK_RXDELAY1 ?

aolofsson · 2016-01-19T23:08:35Z

The following should work:

idelay0=0xaaaaaaaa
idleya1=0x0000000a

On Tue, Jan 19, 2016 at 5:00 PM, Ola Jeppsson notifications@github.com
wrote:

@aolofsson https://github.com/aolofsson

Which are the right values for ELINK_RXDELAY0 and ELINK_RXDELAY1 ?

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#37 (comment).

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Cell: +1 781 325 6688
Twitter: @adapteva
Web: adapteva.com

Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

olajep · 2016-01-19T23:13:16Z

thanks, as expected it doesn't fix this issue but I had to test

// Ola

On 2016-01-20 00:08, Andreas Olofsson wrote:

The following should work:

idelay0=0xaaaaaaaa
idleya1=0x0000000a

On Tue, Jan 19, 2016 at 5:00 PM, Ola Jeppsson notifications@github.com
wrote:

@aolofsson https://github.com/aolofsson

Which are the right values for ELINK_RXDELAY0 and ELINK_RXDELAY1 ?

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#37 (comment).

Andreas Olofsson, CEO/Founder at Adapteva
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Twitter: @adapteva
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Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

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aolofsson · 2016-01-19T23:30:55Z

Does the following break?

00000660 <_main>:
660: 0a0b 0552 mov r0,0x5550
664: 354b 0aa2 mov r1,0xaaaa

668: 460b 0072 mov r2,0x0000*
66c: 0aab 1552 movt r0,0x5555
670: 354b 1aa2 movt r1,0xaaaa
674: 41eb 1812 movt r2,0x8f10*
678: 0874 strd r0,[r2]
67a: 01a2 nop
67c: 01a2 nop
67e: 01a2 nop
680: 01a2 nop
682: 01a2 nop
684: 01a2 nop
686: 0a0b 0552 mov r0,0x5550
68a: 354b 0aa2 mov r1,0xaaaa
68e: 0aab 1552 movt r0,0x5555
692: 354b 1aa2 movt r1,0xaaaa
696: 0874 strd r0,[r2]
698: 01a2 nop
...

On Tue, Jan 19, 2016 at 6:13 PM, Ola Jeppsson notifications@github.com
wrote:

thanks, as expected it doesn't fix this issue but I had to test

// Ola

On 2016-01-20 00:08, Andreas Olofsson wrote:

The following should work:

idelay0=0xaaaaaaaa
idleya1=0x0000000a

On Tue, Jan 19, 2016 at 5:00 PM, Ola Jeppsson notifications@github.com
wrote:

@aolofsson https://github.com/aolofsson

Which are the right values for ELINK_RXDELAY0 and ELINK_RXDELAY1 ?

—
Reply to this email directly or view it on GitHub
#37 (comment).

Andreas Olofsson, CEO/Founder at Adapteva
Cell: +1 781 325 6688
Twitter: @adapteva
Web: adapteva.com

Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

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https://github.com/parallella/oh/issues/37#issuecomment-173017631>.

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#37 (comment).

Andreas Olofsson, CEO/Founder at Adapteva
Cell: +1 781 325 6688
Twitter: @adapteva
Web: adapteva.com

Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

olajep · 2016-01-19T23:33:11Z

The reason we may not have see this is that you wrote a tight assembly
loop. Our other tests either use DMA (streaming) or slow C code loops. (in
other words our elink test regression still needs major work!) Would ftest,
matmul, etc code have the same sequence that you wrote in assembly for
mailbox test?

This works (will check in complete test tomorrow)

FUNC(etest)
.global SYM(etest)
.align 3
SYM(etest):
    mov r20, %low(EXPECTED_0)
    movt    r20, %high(EXPECTED_0)
    mov r21, %low(EXPECTED_1)
    movt    r21, %high(EXPECTED_1)
    mov r22, %low(EXPECTED_2)
    movt    r22, %high(EXPECTED_2)
    mov r23, %low(EXPECTED_3)
    movt    r23, %high(EXPECTED_3)
    mov r24, %low(EXPECTED_4)
    movt    r24, %high(EXPECTED_4)
    mov r25, %low(EXPECTED_5)
    movt    r25, %high(EXPECTED_5)
    mov r26, %low(EXPECTED_6)
    movt    r26, %high(EXPECTED_6)
    mov r27, %low(EXPECTED_7)
    movt    r27, %high(EXPECTED_7)

    mov r30, %low(RESULT_ADDR)
    movt    r30, %high(RESULT_ADDR)

    str r20,[r30],+1
    str r21,[r30],+1
    str r22,[r30],+1
    str r23,[r30],+1
    str r24,[r30],+1
    str r25,[r30],+1
    str r26,[r30],+1
    str r27,[r30],+1

    ;; repeat w/ 64-bit writes
    strd    r20,[r30],+1
    strd    r22,[r30],+1
    strd    r24,[r30],+1
    strd    r26,[r30],+1

    rts

olajep · 2016-01-19T23:38:29Z

(result_addr is in DRAM)

aolofsson · 2016-01-20T04:32:14Z

Found the bug!! NASTY!!!!!

Remembered that we have a long forgotten mode in the epiphany chip elink
(not impemented in the fpga elink) that creates bursts when you write
doubles to the same address. (F**K!)
So the writes were likely coming in as bursts.
Looks like the mailbox works fine when you write in "int"s (I tested it on
the board with consecutive)
(see "mailbox_test" in elink/sw0)

Should not be a big deal to implement burst with increment set to 0 instead
of 8, for now let's work with ints.

Please verify.

On Tue, Jan 19, 2016 at 6:38 PM, Ola Jeppsson notifications@github.com
wrote:

(result_addr is in DRAM)

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#37 (comment).

Andreas Olofsson, CEO/Founder at Adapteva
Cell: +1 781 325 6688
Twitter: @adapteva
Web: adapteva.com

Linkedin: linkedin.com/in/andreasolofsson

http://www.adapteva.com/

olajep · 2016-01-20T11:01:11Z

32-bit (str) writes work with 1f42630

Add test for writes to same address. Apparently consecutive 64-bit writes to the same address can turn into burst writes. From: aolofsson#37 Andreas: > Remembered that we have a long forgotten mode in the epiphany chip elink > (not impemented in the fpga elink) that creates bursts when you write > doubles to the same address. (F**K!) > So the writes were likely coming in as bursts. > Looks like the mailbox works fine when you write in "int"s (I tested it on > the board with consecutive) > (see "mailbox_test" in elink/sw0) Signed-off-by: Ola Jeppsson <ola@adapteva.com>

F1xes aolofsson#37 Testcase: [src]/elink/sw/burst-test aolofsson commented on Jan 20, 2016 >Found the bug!! NASTY!!!!! > >Remembered that we have a long forgotten mode in the epiphany chip elink >(not impemented in the fpga elink) that creates bursts when you write >doubles to the same address. (F**K!) >So the writes were likely coming in as bursts. >Looks like the mailbox works fine when you write in "int"s (I tested it on >the board with consecutive) >(see "mailbox_test" in elink/sw0) Well, this mysterious mode is not mentioned in any documentation I can find but as it turns out it's implemented in the old elink gold here: https://github.com/parallella/parallella-hw/blob/635227356a946f8/fpga/hdl/elink-gold/ewrapper_link_rxi.v#L518 Signed-off-by: Ola Jeppsson <ola@adapteva.com>

olajep mentioned this issue Jan 20, 2016

Add burst test #39

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mailbox: Writes dissapear #37

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mailbox: Writes dissapear #37

mailbox: Writes dissapear #37

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