UPDI data breakpoint(s)?

[urjaman]

Okay, so, i added support for attiny3217, and the first thing i tried to do was to watch a global 8-bit variable and run, like this:

[urjaman@veyron bikeoledsw]$ ~/avr-tools8/bin/avr-gdb bikeoled.out 
GNU gdb (GDB) 13.0.50.20221120-git
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Type "show copying" and "show warranty" for details.
This GDB was configured as "--host=armv7l-unknown-linux-gnueabihf --target=avr".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from bikeoled.out...
(gdb) target remote :4242
Remote debugging using :4242
0x00000000 in __vectors ()
(gdb) watch pulses_per_rotation
Hardware watchpoint 1: pulses_per_rotation
(gdb) continue
Continuing.
Remote connection closed
(gdb) 

Meanwhile avarice reported this:

[urjaman@veyron bikeoledsw]$ ~/avr-tools8/bin/avarice -d -4 -u -P attiny3217 :4242 
AVaRICE version 2.14svn20200906, Jul 21 2023 23:07:55

Found HID PID:VID 0x03eb:0x2141, serno J41800058896
Probing for HID max. packet size
Setting max. packet size to 512 from DAP_Info
HID thread started
JTAG config starting.

command "sign-on" [0x01, 0x10]
0E 00 00 00 01 10 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x00
read:  0e 00 00 01 80 00

Got message seqno 0 (command_sequence == 0)
response: 01 80 00 

command "get info (serial number)" [0x00, 0x00]
0E 00 01 00 00 00 00 81 
Received 0x81 0x11 0x00 0x12 0x0e 0x01
read:  0e 01 00 00 81 00 4a 34 31 38 30 30 30 35 38 38 39 36

Got message seqno 1 (command_sequence == 1)
response: 00 81 00 4A 34 31 38 30 30 30 35 38 38 39 36 
Found a device, serial number: J41800058896

command "get parameter" [0x01, 0x02]
0E 00 02 00 01 02 00 00 00 05 
Received 0x81 0x11 0x00 0x0c 0x0e 0x02
read:  0e 02 00 01 84 01 00 01 29 89 00 00

Got message seqno 2 (command_sequence == 2)
response: 01 84 01 00 01 29 89 00 00 
ICE hardware version: 0
ICE firmware version: 1.41 (rel. 137)

command "set parameter" [0x12, 0x01]
0E 00 03 00 12 01 00 00 00 01 05 
Received 0x81 0x11 0x00 0x06 0x0e 0x03
read:  0e 03 00 12 80 00

Got message seqno 3 (command_sequence == 3)
response: 12 80 00 

command "set parameter" [0x12, 0x01]
0E 00 04 00 12 01 00 00 01 01 02 
Received 0x81 0x11 0x00 0x06 0x0e 0x04
read:  0e 04 00 12 80 00

Got message seqno 4 (command_sequence == 4)
response: 12 80 00 

command "set parameter" [0x12, 0x01]
0E 00 05 00 12 01 00 01 00 01 08 
Received 0x81 0x11 0x00 0x06 0x0e 0x05
read:  0e 05 00 12 80 00

Got message seqno 5 (command_sequence == 5)
response: 12 80 00 

command "set parameter" [0x12, 0x01]
0E 00 06 00 12 01 00 02 00 08 00 40 80 40 00 10 80 0F 
Received 0x81 0x11 0x00 0x06 0x0e 0x06
read:  0e 06 00 12 80 00

Got message seqno 6 (command_sequence == 6)
response: 12 80 00 

command "AVR sign-on" [0x12, 0x10]
0E 00 07 00 12 10 00 00 
Received 0x81 0x11 0x00 0x0b 0x0e 0x07
read:  0e 07 00 12 84 00 74 69 6e 79 00

Got message seqno 7 (command_sequence == 7)
response: 12 84 00 74 69 6E 79 00 
AVR sign-on responded with tiny
Automatic device detection: jtagRead 
command "enter progmode" [0x12, 0x15]
0E 00 08 00 12 15 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x08
read:  0e 08 00 12 80 00

Got message seqno 8 (command_sequence == 8)
response: 12 80 00 

command "read memory" [0x12, 0x21]
0E 00 09 00 12 21 00 B4 00 11 00 00 03 00 00 00 
Received 0x81 0x11 0x00 0x0a 0x0e 0x09
read:  0e 09 00 12 84 00 1e 95 22 00

Got message seqno 9 (command_sequence == 9)
response: 12 84 00 1E 95 22 00 

command "leave progmode" [0x12, 0x16]
0E 00 0A 00 12 16 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x0a
read:  0e 0a 00 12 80 00

Got message seqno 10 (command_sequence == 10)
response: 12 80 00 
Reported device ID: 0x9522
Looking for device: attiny3217
Configured for device ID: 0x9522 attiny3217 -- Matched with attiny3217

command "set parameter" [0x12, 0x01]
0E 00 0B 00 12 01 00 02 00 08 00 80 80 40 00 10 80 0F 
Received 0x81 0x11 0x00 0x06 0x0e 0x0b
read:  0e 0b 00 12 80 00

Got message seqno 11 (command_sequence == 11)
response: 12 80 00 
JTAG config complete.
Preparing the target device for On Chip Debugging.

command "set parameter" [0x12, 0x01]
0E 00 0C 00 12 01 00 03 00 01 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x0c
read:  0e 0c 00 12 80 00

Got message seqno 12 (command_sequence == 12)
response: 12 80 00 

command "reset" [0x12, 0x30]
0E 00 0D 00 12 30 00 01 
Received 0x81 0x11 0x00 0x06 0x0e 0x0d
read:  0e 0d 00 12 80 00

Got message seqno 13 (command_sequence == 13)
response: 12 80 00 
read:  0e 00 02 00 12 40 00 00 00 00 01 84 00 30
Event serial 0x0002
caching PC: 0x0000
Waiting for connection on port 4242.
Connection opened by host 127.0.0.1, port 40962.
GDB: <qSupported:multiprocess+;swbreak+;hwbreak+;qRelocInsn+;fork-events+;vfork-events+;exec-events+;vContSupported+;QThreadEvents+;no-resumed+;memory-tagging+>
->GDB: PacketSize=40;qXfer:memory-map:read+
GDB: <vMustReplyEmpty>
->GDB: 
GDB: <Hg0>
->GDB: 
GDB: <qTStatus>
->GDB: 
GDB: <?>
->GDB: S05
GDB: <qfThreadInfo>
->GDB: 
GDB: <qL1020000000000000000>
->GDB: 
GDB: <Hc-1>
->GDB: 
GDB: <qC>
->GDB: 
GDB: <qAttached>
->GDB: 
GDB: <qOffsets>
->GDB: 
GDB: <g>

GDB: (Registers)Read 32 bytes from 0x800000
jtagRead 
command "read memory" [0x12, 0x21]
0E 00 0E 00 12 21 00 20 00 00 00 00 20 00 00 00 
Received 0x81 0x11 0x00 0x27 0x0e 0x0e
read:  0e 0e 00 12 84 00 00 00 7e 00 00 00 03 00 00 00 3f 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Got message seqno 14 (command_sequence == 14)
response: 12 84 00 00 00 7E 00 00 00 03 00 00 00 3F 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
jtagRead 
command "read memory" [0x12, 0x21]
0E 00 0F 00 12 21 00 20 5D 00 00 00 03 00 00 00 
Received 0x81 0x11 0x00 0x0a 0x0e 0x0f
read:  0e 0f 00 12 84 00 00 00 00 00

Got message seqno 15 (command_sequence == 15)
response: 12 84 00 00 00 00 00 

command "read PC" [0x12, 0x35]
0E 00 10 00 12 35 00 
Received 0x81 0x11 0x00 0x0a 0x0e 0x10
read:  0e 10 00 12 83 00 00 00 00 00

Got message seqno 16 (command_sequence == 16)
response: 12 83 00 00 00 00 00 
PC = 0
->GDB: 00007e000000030000003f00000000000000000000000000000000000000000000000000000000
GDB: <qL1020000000000000000>
->GDB: 
GDB: <qSymbol::>
->GDB: 
GDB: <qXfer:memory-map:read::0,3b>
->GDB: l<memory-map>
  <memory type="ram" start="0x800000" length="0x20000" />
  <memory type="flash" start="0" length="0x8000">
     <property name="blocksize">0x80</property>
  </memory>
</memory-map>

GDB: <m803801,1>

GDB: Read 1 bytes from 0x803801
jtagRead 
command "read memory" [0x12, 0x21]
0E 00 11 00 12 21 00 20 01 38 00 00 01 00 00 00 
Received 0x81 0x11 0x00 0x08 0x0e 0x11
read:  0e 11 00 12 84 00 07 00

Got message seqno 17 (command_sequence == 17)
response: 12 84 00 07 00 
->GDB: 07
GDB: <m803801,1>

GDB: Read 1 bytes from 0x803801
jtagRead 
command "read memory" [0x12, 0x21]
0E 00 12 00 12 21 00 20 01 38 00 00 01 00 00 00 
Received 0x81 0x11 0x00 0x08 0x0e 0x12
read:  0e 12 00 12 84 00 07 00

Got message seqno 18 (command_sequence == 18)
response: 12 84 00 07 00 
->GDB: 07
GDB: <Z2,803801,1>
BP ADD type: 2  addr: 0x803801 ->GDB: OK
GDB: <vCont?>
->GDB: 
GDB: <Hc0>
->GDB: 
GDB: <c>
Breakpoint added in ICE. slot: 2  type: 2  addr: 0x803801

command "set BP" [0x12, 0x40]
0E 00 13 00 12 40 00 02 02 01 38 00 00 01 
Received 0x81 0x11 0x00 0x07 0x0e 0x13
read:  0e 13 00 12 a0 00 80

Got message seqno 19 (command_sequence == 19)
response: 12 A0 00 80 
Failed to set breakpoint: Unknown response code 0x80

command "stop debugging" [0x12, 0x14]
0E 00 14 00 12 14 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x14
read:  0e 14 00 12 80 00

Got message seqno 20 (command_sequence == 20)
response: 12 80 00 

command "AVR sign-off" [0x12, 0x11]
0E 00 15 00 12 11 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x15
read:  0e 15 00 12 80 00

Got message seqno 21 (command_sequence == 21)
response: 12 80 00 

command "sign-off" [0x01, 0x11]
0E 00 16 00 01 11 00 
Received 0x81 0x11 0x00 0x06 0x0e 0x16
read:  0e 16 00 01 80 00

Got message seqno 22 (command_sequence == 22)
response: 01 80 00 

That EDBG documentation lists that response as AVR8_FAILURE_ILLEGAL_BREAKPOINT

so I'm assuming UPDI just can't do this (or we're doing it wrong)?

The EDBG doc says UPDI supports one breakpoint, but i'm not sure if it can be a data watchpoint, and then, slot=2 sounds wrong... I dont' have the time to investigate further right now, but wanted to just put this out ASAP.

(Meanwhile i'll put the attiny3217 support patch up...)

[urjaman]

The patch is up (and i'm on a train) -- the device datasheet actually says two hardware breakpoints, but makes no mention of data vs code.

[urjaman]

I loaded up that project for debugging in Microchip (ugh) Studio (yeah you can do that, you just need to configure avr-gcc for -gdwarf-2 ...), and tried to set the same data breakpoint:

I think that answer that, there are no data breakpoints for ATtiny3217. Now i need to investigate how to make avarice expose that properly to gdb..

[urjaman]

So i've figured this stuff out; i'll be reporting the details in a (WIP) PR, no point to leave this dangling, so closing.