[PATCH] tty: hvc_dcc: Add basic early_con support
From: nm@ti.com (Nishanth Menon)
Date: 2016-12-20 00:25:45
Also in:
linuxppc-dev, lkml
Subsystem:
hypervisor virtual console driver, the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
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 <nm@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