Messages in this thread | | | Date | Thu, 17 Oct 2013 14:16:37 -0500 | Subject | Re: [PATCH v2] TTY: hvc_dcc: probe for a JTAG connection before registering | From | Rob Herring <> |
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On Tue, Sep 24, 2013 at 9:05 PM, Rob Herring <robherring2@gmail.com> wrote: > From: Rob Herring <rob.herring@calxeda.com> > > 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> > --- > v2: use time_is_after_jiffies > > drivers/tty/hvc/hvc_dcc.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+)
Greg, Jiri,
Can you please apply.
Rob
> > 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; > } > -- > 1.8.1.2 >
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