From c34880f460e6aee75550ef105f1c8aabc3089a68 Mon Sep 17 00:00:00 2001
From: Vadim Bendebury <vbendeb@chromium.org>
Date: Tue, 10 Mar 2020 17:31:19 -0700
Subject: system: avoid printing one character at a time

With the upcoming transition to handling console traffic in packet
mode it is very expensive to be shipping one character at a time, each
character results in sending a packet of 16 or so bytes.

This patch modifies print_build_string() such that it splits the long
build version string into manageable substrings and prints them
instead of printing one character at a time.

BRANCH=cr50, cr50-mp
BUG=b:149964350
TEST=built a Cr50 image, verified that build string is printed as
     expected.

Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Change-Id: I743205932892b0f14c161ade5ea856a658fb26e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2097444
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
---
 common/system.c | 48 +++++++++++++++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 13 deletions(-)

diff --git a/common/system.c b/common/system.c
index 61ef4882fc..036de2235e 100644
--- a/common/system.c
+++ b/common/system.c
@@ -27,6 +27,7 @@
 #include "mpu.h"
 #endif
 #include "panic.h"
+#include "shared_mem.h"
 #include "sysjump.h"
 #include "system.h"
 #include "task.h"
@@ -1016,15 +1017,19 @@ DECLARE_CONSOLE_COMMAND(hibernate, command_hibernate,
 static void print_build_string(void)
 {
 	const char *full_build_string;
-	const char *p;
+	char *p;
 	char symbol;
+	char *next;
+	int index;
+	size_t len;
 	int seen_colonv;
 
 	ccprintf("Build:   ");
 	full_build_string = system_get_build_info();
 
+	len = strlen(full_build_string);
 	/* 50 characters or less, will fit into the terminal line. */
-	if (strlen(full_build_string) < 50) {
+	if (len < 50) {
 		ccprintf("%s\n", full_build_string);
 		return;
 	}
@@ -1034,24 +1039,41 @@ static void print_build_string(void)
 	 * space (this is where the main version ends), and then on each space
 	 * after the ":v" substring, this is where subcomponent versions are
 	 * separated.
+	 *
+	 * To avoid invoking ccprintf() for one character at a time let's
+	 * create a mutable copy and modify it to print in multiple lines.
 	 */
-	p = full_build_string;
+	if (shared_mem_acquire(len + 1, &p) != EC_SUCCESS) {
+		/*
+		 * Should never happen, but if it does let's
+		 * just print it in single line.
+		 */
+		ccprintf("%s\n", full_build_string);
+		return;
+	}
+
+	memcpy(p, full_build_string, len + 1);
+	next = p;
+	index = 0;
 	seen_colonv = 1;
 
-	symbol = *p++;
-	while (symbol) {
+	do {
+		symbol = next[index++];
 		if ((symbol == ' ') && seen_colonv) {
+			next[index - 1] = '\0';
 			seen_colonv = 0;
 			/* Indent each line under 'Build:    ' */
-			ccprintf("\n         ");
-		} else {
-			if ((symbol == ':') && (*p == 'v'))
-				seen_colonv = 1;
-			ccprintf("%c", symbol);
+			ccprintf("%s\n         ", next);
+			next += index;
+			index = 0;
+			continue;
 		}
-		symbol = *p++;
-	}
-	ccprintf("\n");
+		if ((symbol == ':') && (next[index] == 'v'))
+			seen_colonv = 1;
+	} while (symbol);
+	ccprintf("%s\n", next);
+
+	shared_mem_release(p);
 }
 
 static int command_version(int argc, char **argv)
-- 
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