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Date:      Thu, 25 Jul 2019 18:22:53 +0000
From:      Robert Crowston <crowston@protonmail.com>
To:        David Cornejo <dave@dogwood.com>
Cc:        "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>
Subject:   Re: Raspberry Pi 4 boot hangs in sched_idletd.
Message-ID:  <UH6AEnBTWndK0E0sZDI5vGcKC84-9Zy9mFSRBaq5N23JAtyu2R3YFznJTGAhMPbZWWfZVZaEr_IRziWVlVu8jEIhtbcL7lwDdFB2eYCEvOo=@protonmail.com>
In-Reply-To: <CAFnjQbt3TNdjgis2sZ7vrH0nsiP3R-i3zaQ0FtjL1hmZr6gMcQ@mail.gmail.com>
References:  <bZhr6z5_4M6PcYR8ZarvkmvnLEb9KLGiBgffRczi8BR8tGB4FzDhvddWuubPAJCuRfebzCJA2Uf5RSd9dUF4tNkkhRa9Pn27ruXia9s2C_M=@protonmail.com> <CAFnjQbt3TNdjgis2sZ7vrH0nsiP3R-i3zaQ0FtjL1hmZr6gMcQ@mail.gmail.com>

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> Is there some sort of guide or instructions for using a JTAG debugger
> on the FreeBSD kernel available somewhere?

I haven't seen anything. Once you have the JTAG up and running, it typicall=
y presents itself to you as an GDB server, so you connect to it from gdb, a=
dd the symbols for your kernel so you can make sense of what's going on, an=
d treat it much like a regular executable.

I found this page invaluable for the configuration needed to work on the Pi=
: https://metebalci.com/blog/bare-metal-raspberry-pi-3b-jtag/#enabling-jtag=
-on-raspberry-pi
I use this USB-attached JTAG: https://uk.farnell.com/ftdi/c232hm-ddhsl-0/ca=
ble-usb-mpsse-0-25a-3-3v-o-p/dp/2352015?CMP=3Di-ddd7-00001003 (on a MacBook=
)

You'll need to build openOCD and a version of gdb targeting your intended a=
rchitecture.

There are a few hoops to jump through but I don't think it's too difficult =
at all.

Let me know if you get stuck.



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