07:18 <ayaka_> is possible that set different adapter speeds for different target? likes we have many Access ports in a DAP, some of them can't work in a higher speed

08:03 <borneoa___> ayaka_: the adapter speed is only one and is the speed of the JTAG or SWD clock. But there is a parameter configurable on each access port that is the delay between request and response. I don't remember the command .... I need to check the manual....

08:06 <ayaka_> because adjusting the delay is a little complex, than just adjusting the clock speed

08:10 <Hawk777> dap memaccess IIRC

08:12 <borneoa___> Hawk777: yes, thanks!

08:14 <borneoa___> ayaka_: the command is a little tricky because you have to select that AP with dap apsel, then set the value with memaccess. Humm, but that's for JTAG only...

08:21 <ayaka_> I see, I only use JTAG port now. I would try every APs then

08:30 <ayaka_> while there is still a critical problem for me, only software breakpoint would work but not hardware breakpoint

08:31 <ayaka_> I read this https://developer.arm.com/documentation/ddi0601/2023-09/External-Registers/DBGBVR-n--EL1--Debug-Breakpoint-Value-Registers it seems that the code running from cpu could clear those registers which are set from external debugger?

09:20 <ayaka_> Another idea which could is using a https://elixir.bootlin.com/linux/latest/source/samples/hw_breakpoint/data_breakpoint.c#L49 then trap the handler in software breakpoint

09:20 <ayaka_> but gdb would refuse to help in this way(cannot read system control register in this mode: (USR : 0x10))

17:52 <borneoa___> ayaka: yes linux erases all HW breakpoints during boot. You can avoid it by adding to the cmdline: initcall_blacklist=arch_hw_breakpoint_init

18:03 <karlp> thatsounds like helpful most of the time, but "why is this your business linux?!" the rest of the time :)

18:20 <bencoh> uh, that's good to know

19:13 <borneoa___> karlp: I think linux uses the debug unit for some tracing process. And probably for KGDB

20:21 <karlp> yeah, I know it's a compilcated world :)