mbox series

[RFC,0/3] Add DCC uart console support

Message ID 20240614093026.328271-1-sai.pavan.boddu@amd.com (mailing list archive)
Headers show
Series Add DCC uart console support | expand

Message

Sai Pavan Boddu June 14, 2024, 9:30 a.m. UTC 
This patch series attaches a chardev to  arm Debug Communication channel registers,
As each cpu has it own DBGDTRTX/RX register just tried to hook each cpu
with chardev iff we find a chardev with id "dcc<cpu-id>".

ex:
    Below chardev switch would be connected to A53-0.

    ./qemu-system-aarch64 -M xlnx-zcu102 -kernel u-boot-dtb.bin
      -dtb zynqmp-zcu102-rev1.1.d -display none -m 2G
      -chardev stdio,id=dcc0


Sai Pavan Boddu (3):
  target/arm: Add dcc uart support
  target/arm: Enable dcc console for a53 and R5
  target/arm/debug_helper: Add fieldoffset for MDCCSR_EL0 reg

 target/arm/cpu.h          | 11 +++++
 target/arm/internals.h    |  4 ++
 target/arm/cpu64.c        |  1 +
 target/arm/debug-dcc.c    | 99 +++++++++++++++++++++++++++++++++++++++
 target/arm/debug_helper.c |  2 +-
 target/arm/helper.c       |  3 ++
 target/arm/tcg/cpu32.c    |  1 +
 target/arm/meson.build    |  1 +
 8 files changed, 121 insertions(+), 1 deletion(-)
 create mode 100644 target/arm/debug-dcc.c

Comments

Peter Maydell June 21, 2024, 3:28 p.m. UTC | #1 
On Fri, 14 Jun 2024 at 10:30, Sai Pavan Boddu <sai.pavan.boddu@amd.com> wrote:
>
> This patch series attaches a chardev to  arm Debug Communication channel registers,
> As each cpu has it own DBGDTRTX/RX register just tried to hook each cpu
> with chardev iff we find a chardev with id "dcc<cpu-id>".
>
> ex:
>     Below chardev switch would be connected to A53-0.
>
>     ./qemu-system-aarch64 -M xlnx-zcu102 -kernel u-boot-dtb.bin
>       -dtb zynqmp-zcu102-rev1.1.d -display none -m 2G
>       -chardev stdio,id=dcc0

This is neat -- I've thought before that it would be nice to be able
to use the DCC as a chardev destination, given that Linux has support
for earlycon-over-DCC. The thing that put me off was the question
of what the command-line syntax for setting it up ought to be, though.
I'm not sure we want "look for the chardev with a particular ID string"
but I don't know what existing in-tree precedent we have for this
kind of thing.

thanks
-- PMM