In some cases, earlycon can help catch errors with kernel boot prior to
standard console is available.
Example bootargs: console=hvc0 earlycon=hvcdcc
Signed-off-by: Nishanth Menon <n...@ti.com>
---
Based on: v4.9 tag
Also applies on: next-20161219
Tested on Simulation environment (which did not have serial console option)
drivers/tty/hvc/hvc_dcc.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c
index 82f240fb98f0..1ec06e550656 100644
--- a/drivers/tty/hvc/hvc_dcc.c
+++ b/drivers/tty/hvc/hvc_dcc.c
@@ -10,7 +10,9 @@
* GNU General Public License for more details.
*/
+#include <linux/console.h>
#include <linux/init.h>
+#include <linux/serial_core.h>
#include <asm/dcc.h>
#include <asm/processor.h>
@@ -94,3 +96,45 @@ static int __init hvc_dcc_init(void)
return PTR_ERR_OR_ZERO(p);
}
device_initcall(hvc_dcc_init);
+
+static int hvc_dcc_earlyputc(int c)
+{
+ unsigned long count = 0xFFFFFFFF;
+ static bool dead_dcc_earlycon;
+
+ if (dead_dcc_earlycon)
+ return -EBUSY;
+
+ while (count--) {
+ if (!(__dcc_getstatus() & DCC_STATUS_TX))
+ break;
+ }
+ if (!count) {
+ dead_dcc_earlycon = true;
+ return -EBUSY;
+ }
+ __dcc_putchar(c);
+ return 0;
+}
+
+static void hvc_dcc_earlywrite(struct console *con, const char *s,
+ unsigned int n)
+{
+ int r;
+
+ while (n--) {
+ r = hvc_dcc_earlyputc(*s);
+ if (r)
+ break;
+ s++;
+ }
+}
+
+static int
+__init early_hvc_dcc_setup(struct earlycon_device *device, const char *opt)
+{
+ device->con->write = hvc_dcc_earlywrite;
+ return 0;
+}
+
+EARLYCON_DECLARE(hvcdcc, early_hvc_dcc_setup);
--
2.11.0.65.geff96d7
