4.4-stable review patch. If anyone has any objections, please let me know.
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From: Tony Lindgren tony@atomide.com
commit b2d89ad9c9682e795ed6eeb9ed455789ad6cedf1 upstream.
At least on droid 4 with control channel in ADM mode, there is no response to Modem Status Command (MSC). Currently gsmtty_modem_update() expects to have data in dlci->modem_rx unless debug & 2 is set. This means that on droid 4, things only work if debug & 2 is set.
Let's fix the issue by ignoring empty dlci->modem_rx for ADM mode. In the AMD mode, CMD_MSC will never respond and gsm_process_modem() won't get called to set dlci->modem_rx.
And according to ts_127010v140000p.pdf, MSC is only relevant if basic option is chosen, so let's test for that too.
Fixes: ea3d8465ab9b ("tty: n_gsm: Allow ADM response in addition to UA for control dlci") Cc: linux-serial@vger.kernel.org Cc: Alan Cox alan@llwyncelyn.cymru Cc: Dan Williams dcbw@redhat.com Cc: Jiri Prchal jiri.prchal@aksignal.cz Cc: Jiri Slaby jslaby@suse.cz Cc: Marcel Partap mpartap@gmx.net Cc: Merlijn Wajer merlijn@wizzup.org Cc: Michael Nazzareno Trimarchi michael@amarulasolutions.com Cc: Michael Scott michael.scott@linaro.org Cc: Pavel Machek pavel@ucw.cz Cc: Peter Hurley peter@hurleysoftware.com Cc: Russ Gorby russ.gorby@intel.com Cc: Sascha Hauer s.hauer@pengutronix.de Cc: Sebastian Reichel sre@kernel.org Signed-off-by: Tony Lindgren tony@atomide.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/tty/n_gsm.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
--- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2891,11 +2891,22 @@ static int gsmtty_modem_update(struct gs 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; }