zephyr: switch to using shell_*, not printk

Reimplement the printf functions for Zephyr to use shell_* functions
instead of printk.

The main differences are:
-UART output is buffered by the shell layer. The size of the buffer
should be adjusted per board (SHELL_BACKEND_SERIAL_TX_RING_BUFFER_SIZE)
-The shell uses non-blocking UART FIFO operations while printk waits
actively for every sent byte.
-The shell prints can not be split by the other shell prints so it
should increase the quality of the output. However the shell_* functions
can not be used in interrupts, so use printk instead which can divide
the shell output. The output may be messy for boards that have a lot
of prints in interrupts e.g. volteer.

EC uses unusual print format e.g. "%pT" to print a timestamp, so use the
CrosEC's vfnprintf function and then pass the generated string to the
shell_* print. Use the sprintf function for that purpose.
Long term, the EC codebase should switch to a usual print format,
so shell_* can be used directly and not 2 versions of vfnprintf.

This change should also help to pass tests that wait for a certain
pattern on output e.g. ECBootTime.

BUG=b:191724484, b:178033156
BRANCH=none
TEST=Verify the console output works

Signed-off-by: Dawid Niedzwiecki <dn@semihalf.com>
Change-Id: Ifaed2093ab8c43038c7d3e0ded1449a93f7f7da5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2988194
Reviewed-by: Keith Short <keithshort@chromium.org>
Commit-Queue: Keith Short <keithshort@chromium.org>

0 files changed, 0 insertions, 0 deletions