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>

1 files changed, 3 insertions, 10 deletions

diff --git a/common/printf.c b/common/printf.c
index 14226800b6..be06d34dd8 100644
--- a/common/printf.c
+++ b/common/printf.c
@@ -463,12 +463,6 @@ int vfnprintf(int (*addchar)(void *context, int c), void *context,
 	return EC_SUCCESS;
 }
 
-/*
- * These symbols are already defined by the Zephyr OS kernel, and we
- * don't want to use the EC implementation.
- */
-#ifndef CONFIG_ZEPHYR
-
 /* Context for snprintf() */
 struct snprintf_context {
 	char *str;
@@ -494,19 +488,19 @@ static int snprintf_addchar(void *context, int c)
 	return 0;
 }
 
-int snprintf(char *str, size_t size, const char *format, ...)
+int crec_snprintf(char *str, size_t size, const char *format, ...)
 {
 	va_list args;
 	int rv;
 
 	va_start(args, format);
-	rv = vsnprintf(str, size, format, args);
+	rv = crec_vsnprintf(str, size, format, args);
 	va_end(args);
 
 	return rv;
 }
 
-int vsnprintf(char *str, size_t size, const char *format, va_list args)
+int crec_vsnprintf(char *str, size_t size, const char *format, va_list args)
 {
 	struct snprintf_context ctx;
 	int rv;
@@ -525,4 +519,3 @@ int vsnprintf(char *str, size_t size, const char *format, va_list args)
 	return (rv == EC_SUCCESS) ? (ctx.str - str) : -rv;
 }
 
-#endif /* !CONFIG_ZEPHYR */