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authorRob Herring <rob.herring@calxeda.com>2013-09-24 21:05:58 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-09-25 18:10:56 -0700
commitf377775dc083506e2fd7739d8615971c46b5246e (patch)
tree9fac95e32736d6a172db90ccc376043af9ef039c /drivers/tty/hvc/hvc_dcc.c
parent469d6d0631386e6865a30c9ded87a5cc0fdf8e2e (diff)
downloadop-kernel-dev-f377775dc083506e2fd7739d8615971c46b5246e.zip
op-kernel-dev-f377775dc083506e2fd7739d8615971c46b5246e.tar.gz
TTY: hvc_dcc: probe for a JTAG connection before registering
Enabling the ARM DCC console and using without a JTAG connection will simply hang the system. Since distros like to turn on all options, this is a reoccurring problem to debug. We can do better by checking if anything is attached and handling characters. There is no way to probe this, so send a newline and check that it is handled. Cc: Paolo Pisati <paolo.pisati@canonical.com> Cc: Tim Gardner <tim.gardner@canonical.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jslaby@suse.cz> Signed-off-by: Rob Herring <rob.herring@calxeda.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/hvc/hvc_dcc.c')
-rw-r--r--drivers/tty/hvc/hvc_dcc.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c
index 44fbeba..3502a7b 100644
--- a/drivers/tty/hvc/hvc_dcc.c
+++ b/drivers/tty/hvc/hvc_dcc.c
@@ -86,6 +86,21 @@ static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
return i;
}
+static bool hvc_dcc_check(void)
+{
+ unsigned long time = jiffies + (HZ / 10);
+
+ /* Write a test character to check if it is handled */
+ __dcc_putchar('\n');
+
+ while (time_is_after_jiffies(time)) {
+ if (!(__dcc_getstatus() & DCC_STATUS_TX))
+ return true;
+ }
+
+ return false;
+}
+
static const struct hv_ops hvc_dcc_get_put_ops = {
.get_chars = hvc_dcc_get_chars,
.put_chars = hvc_dcc_put_chars,
@@ -93,6 +108,9 @@ static const struct hv_ops hvc_dcc_get_put_ops = {
static int __init hvc_dcc_console_init(void)
{
+ if (!hvc_dcc_check())
+ return -ENODEV;
+
hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
return 0;
}
@@ -100,6 +118,9 @@ console_initcall(hvc_dcc_console_init);
static int __init hvc_dcc_init(void)
{
+ if (!hvc_dcc_check())
+ return -ENODEV;
+
hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
return 0;
}
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