diff options
| author |   Rob Herring <rob.herring@calxeda.com> | 2013-09-24 21:05:58 -0500 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-09-25 18:10:56 -0700 |
| commit | f377775dc083506e2fd7739d8615971c46b5246e (patch) | |
| tree | 9fac95e32736d6a172db90ccc376043af9ef039c /drivers/tty/hvc | |
| parent | tty: Remove unused drop() method from tty_port interface (diff) | |
| download | linux-dev-f377775dc083506e2fd7739d8615971c46b5246e.tar.xz linux-dev-f377775dc083506e2fd7739d8615971c46b5246e.zip | |
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')
| -rw-r--r-- | drivers/tty/hvc/hvc_dcc.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/tty/hvc/hvc_dcc.c b/drivers/tty/hvc/hvc_dcc.c index 44fbebab5075..3502a7bbb69e 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; } |