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Diffstat (limited to 'drivers/tty/n_gsm.c')
-rw-r--r--drivers/tty/n_gsm.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 7b1f8636f8e9..1dbe27c9946c 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2871,11 +2871,22 @@ static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
static int gsm_carrier_raised(struct tty_port *port)
{
struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
+ struct gsm_mux *gsm = dlci->gsm;
+
/* Not yet open so no carrier info */
if (dlci->state != DLCI_OPEN)
return 0;
if (debug & 2)
return 1;
+
+ /*
+ * Basic mode with control channel in ADM mode may not respond
+ * to CMD_MSC at all and modem_rx is empty.
+ */
+ if (gsm->encoding == 0 && gsm->dlci[0]->mode == DLCI_MODE_ADM &&
+ !dlci->modem_rx)
+ return 1;
+
return dlci->modem_rx & TIOCM_CD;
}