[PATCH v2] netconsole: various improvements

[Tony Dinh]

Use CONFIG_CONSOLE_MUX for netconsole. When netconsole is running,
stdin/stdout/stder must be set to some primary console, in addtion to nc.
For example, stdin=serial,nc. Some recent Linux kernels will not boot with
only nc on the stdout list, ie. stdout=nc. When netconsole exits, remove
nc from the list of devices in stdin/stdout/stderr.

Signed-off-by: Tony Dinh <mibodhi at gmail.com>
---

Changes in v2:
- Select CONFIG_CONSOLE_MUX if CONFIG_NETCONSOLE is enabled
- Add new functions in netconsole driver to support CONSOLE_MUX
- Add new function to encapsulate the process of stopping netconsole
from bootm
- Remove unecessary net_timeout initial value = 1

 boot/bootm.c             | 13 ++++++---
 drivers/net/Kconfig      | 10 +++++++
 drivers/net/netconsole.c | 60 ++++++++++++++++++++++++++++++++++++++++
 include/stdio_dev.h      |  1 +
 4 files changed, 80 insertions(+), 4 deletions(-)

diff --git a/boot/bootm.c b/boot/bootm.c
index 2eec60ec7b..11203c01ec 100644
--- a/boot/bootm.c
+++ b/boot/bootm.c
@@ -472,11 +472,16 @@ ulong bootm_disable_interrupts(void)
 	 * recover from any failures any more...
 	 */
 	iflag = disable_interrupts();
-#ifdef CONFIG_NETCONSOLE
-	/* Stop the ethernet stack if NetConsole could have left it up */
-	eth_halt();
-#endif
 
+	if (IS_ENABLED(CONFIG_NETCONSOLE)) {
+		/*
+		 * Make sure that the starting kernel message printed out,
+		 * stop netconsole and the ethernet stack
+		 */
+		printf("\n\nStarting kernel ...\n\n");
+		drv_nc_stop();
+		eth_halt();
+	}
 #if defined(CONFIG_CMD_USB)
 	/*
 	 * turn off USB to prevent the host controller from writing to the
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index ceadee98a1..0661059dfa 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -945,4 +945,14 @@ config MDIO_MUX_MESON_G12A
 	  This driver is used for the MDIO mux found on the Amlogic G12A & compatible
 	  SoCs.
 
+config NETCONSOLE
+	bool "Enable netconsole"
+	select CONSOLE_MUX
+	help
+	  NetConsole requires CONSOLE_MUX, i.e. at least one default console such
+	  must be specified in addition to nc console. For example, for boards that
+	  the main console is serial, set each of the envs stdin/stdout/stderr to serial,nc.
+	  See CONFIG_CONSOLE_MUX and CONFIG_SYS_CONSOLE_IS_IN_ENV help for detailed
+	  description of usage.
+
 endif # NETDEVICES
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 151bc55e07..bb92d2e130 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -7,6 +7,7 @@
 #include <common.h>
 #include <command.h>
 #include <env.h>
+#include <iomux.h>
 #include <log.h>
 #include <stdio_dev.h>
 #include <net.h>
@@ -33,6 +34,12 @@ static int output_packet_len;
  */
 enum proto_t net_loop_last_protocol = BOOTP;
 
+/*
+ * Net console helpers
+ */
+static void usage(void);
+static void remove_nc_from(const int console);
+
 static void nc_wait_arp_handler(uchar *pkt, unsigned dest,
 				 struct in_addr sip, unsigned src,
 				 unsigned len)
@@ -111,6 +118,21 @@ static int refresh_settings_from_env(void)
 	return 0;
 }
 
+static void remove_nc_from(const int console)
+{
+	int ret;
+
+	ret = iomux_replace_device(console, "nc", "nulldev");
+	if (ret) {
+		printf("\n*** Warning: Cannot remove nc from %s Error=%d\n",
+			stdio_names[console], ret);
+		printf("%s=", stdio_names[console]);
+		iomux_printdevs(console);
+		usage();
+		flush();
+	}
+}
+
 /**
  * Called from net_loop in net/net.c before each packet
  */
@@ -241,6 +263,29 @@ static int nc_stdio_start(struct stdio_dev *dev)
 	return 0;
 }
 
+void nc_stdio_stop(void)
+{
+	if (IS_ENABLED(CONFIG_CONSOLE_MUX)) {
+		int ret;
+		struct stdio_dev *sdev;
+
+		/* Remove nc from each stdio file  */
+		remove_nc_from(stdin);
+		remove_nc_from(stderr);
+		remove_nc_from(stdout);
+
+		/* Deregister nc device */
+		sdev = stdio_get_by_name("nc");
+		ret = stdio_deregister_dev(sdev, true);
+		if (ret)
+			printf("\nWarning: Cannot deregister nc console Error=%d\n", ret);
+	} else {
+		printf("\n*** Warning: CONFIG_CONSOLE_MUX must be enabled for netconsole\n"
+			"to work properly. The nc console will be removed when\n"
+			"netconsole driver stops\n");
+	}
+}
+
 static void nc_stdio_putc(struct stdio_dev *dev, char c)
 {
 	if (output_recursion)
@@ -316,6 +361,16 @@ static int nc_stdio_tstc(struct stdio_dev *dev)
 	return input_size != 0;
 }
 
+static void usage(void)
+{
+	printf("USAGE:\n"
+		"NetConsole requires CONFIG_CONSOLE_MUX. At least one default console\n"
+		"must be specified in addition to nc console. For example, for boards\n"
+		"that the main console is serial, set the each of envs stdin/stdout/stderr\n"
+		"to serial,nc. Some kernel might fail to boot when nc is the only device in\n"
+		"stdout list\n");
+}
+
 int drv_nc_init(void)
 {
 	struct stdio_dev dev;
@@ -335,3 +390,8 @@ int drv_nc_init(void)
 
 	return (rc == 0) ? 1 : rc;
 }
+
+void drv_nc_stop(void)
+{
+	nc_stdio_stop();
+}
diff --git a/include/stdio_dev.h b/include/stdio_dev.h
index 3105928970..9d2375a67e 100644
--- a/include/stdio_dev.h
+++ b/include/stdio_dev.h
@@ -112,6 +112,7 @@ int drv_keyboard_init(void);
 int drv_usbtty_init(void);
 int drv_usbacm_init(void);
 int drv_nc_init(void);
+void drv_nc_stop(void);
 int drv_jtag_console_init(void);
 int cbmemc_init(void);
 
-- 
2.30.2