drivers: gsm_mux: Support GSM 07.10 muxing protocol

Add support to GSM 07.10 muxing protocol which is used to
share the same UART for PPP and AT commands among other things.
This allows e.g., the modem to send SMS and have PPP connection
active at the same time.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>

drivers/console/CMakeLists.txt

@@ -9,3 +9,4 @@ zephyr_sources_if_kconfig(uart_mcumgr.c)
 zephyr_sources_if_kconfig(uart_pipe.c)
 zephyr_sources_if_kconfig(xtensa_sim_console.c)
 zephyr_sources_if_kconfig(native_posix_console.c)
+zephyr_sources_if_kconfig(gsm_mux.c)

drivers/console/Kconfig

@@ -295,4 +295,6 @@ module = UART_CONSOLE
 module-str = UART console
 source "subsys/logging/Kconfig.template.log_config"
 
+source "drivers/console/Kconfig.gsm_mux"
+
 endif

drivers/console/Kconfig.gsm_mux

@@ -0,0 +1,115 @@
+# Copyright (c) 2020 Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+config GSM_MUX
+	bool "Enable GSM 07.10 muxing protocol"
+	help
+	  Enable GSM 07.10 muxing protocol defined in
+	  https://www.etsi.org/deliver/etsi_ts/101300_101399/101369/07.01.00_60/ts_101369v070100p.pdf
+	  The muxing protocol allows GSM modem to share the same UART for both
+	  the PPP data and AT commands.
+
+config GSM_MUX_MAX
+	int "Max number of GSM mux instances"
+	default 1
+	depends on GSM_MUX
+	help
+	  Usually we only need one GSM mux instance. You need to increase
+	  this if you have more than one GSM modems.
+
+config GSM_MUX_DLCI_MAX
+	int "Max number of GSM data link connection (DLC) instances"
+	default 3
+	range 1 64
+	depends on GSM_MUX
+	help
+	  For our purposes we will manage with 3 DLCI (control, ppp, and AT
+	  commands) so making it the default value. If GSM modem also provides
+	  GNSS (location) services and you want to create a DLCI for it, then
+	  you need to increase this to 4.
+
+config GSM_MUX_DLCI_AT
+	int "DLCI id of the AT commands channel"
+	default 2 if MODEM_GSM_SIMCOM
+	default 1
+	range 1 63
+	depends on GSM_MUX
+	help
+	  Channel number for the AT commands to the modem.
+
+config GSM_MUX_DLCI_PPP
+	int "DLCI id of the PPP connection channel"
+	default 1 if MODEM_GSM_SIMCOM
+	default 2
+	range 1 63
+	depends on GSM_MUX
+	help
+	  Channel number for the PPP connection to the modem.
+	  SIMCOM modem has 16kb buffer for DLCI 1 so the manual recommends
+	  it for PPP traffic. For other DLCIs in that modem, the buffer size
+	  is only 1kb.
+
+config GSM_MUX_PENDING_CMD_MAX
+	int "Max number of pending GSM mux commands"
+	default 2
+	range 1 8
+	depends on GSM_MUX
+	help
+	  How many pending GSM mux commands can exists.
+
+config GSM_MUX_MRU_DEFAULT_LEN
+	int "Default size of received user data (MRU)"
+	default 127 if MODEM_GSM_SIMCOM
+	default 31
+	range 1 1509
+	depends on GSM_MUX
+	help
+	  Default MRU (Maximum Receive Unit) data size. The default
+	  value for Basic mode is 31 bytes. The 1509 limit comes from
+	  ublox-sara modem and it means we can transfer full Ethernet sized
+	  frame and muxing headers.
+
+config GSM_MUX_MRU_MAX_LEN
+	int "Max size of received user data (MRU)"
+	default 255 if MODEM_GSM_SIMCOM
+	default 128
+	range 1 1509
+	depends on GSM_MUX
+	help
+	  Max MRU (Maximum Receive Unit) data size. The default max
+	  value for Basic mode is 128 bytes.
+
+config GSM_MUX_INITIATOR
+	bool "Are we the initiator of the connection"
+	default y
+	depends on GSM_MUX
+	help
+	  Default value when deciding whether we are the initiator of the
+	  connection attempt. Normally this should be enabled.
+
+config GSM_MUX_T1_TIMEOUT
+	int "T1 timeout in ms"
+	default 0
+	range 0 5000
+	depends on GSM_MUX
+	help
+	  T1 timeout is initial command timeout when establishing
+	  the connection. The value is in milliseconds. Zero value
+	  means that default (100 ms) specified in the code is used.
+
+if GSM_MUX
+
+module = GSM_MUX
+module-dep = LOG
+module-str = Log level for GSM 07.10 Mux driver
+module-help = Sets log level for GSM 07.10 Mux Device Driver.
+source "subsys/net/Kconfig.template.log_config.net"
+
+config GSM_MUX_VERBOSE_DEBUG
+	bool "Print hexdump of sent and received packets"
+	depends on GSM_MUX_LOG_LEVEL_DBG
+	help
+	  As there might be lot of debug output printed, only enable
+	  this if really needed.
+
+endif

drivers/console/gsm_mux.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2020 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DLCI_CONTROL 0
+#define DLCI_AT      CONFIG_GSM_MUX_DLCI_AT
+#define DLCI_PPP     CONFIG_GSM_MUX_DLCI_PPP
+
+struct gsm_mux;
+struct gsm_dlci;
+
+void gsm_mux_recv_buf(struct gsm_mux *mux, u8_t *buf, int len);
+int gsm_mux_send(struct gsm_mux *mux, u8_t dlci_address,
+		 const u8_t *buf, size_t size);
+struct gsm_mux *gsm_mux_create(struct device *uart);
+int gsm_mux_disconnect(struct gsm_mux *mux, int timeout);
+void gsm_mux_init(void);
+
+typedef void (*gsm_mux_dlci_created_cb_t)(struct gsm_dlci *dlci,
+					  bool connected,
+					  void *user_data);
+
+int gsm_dlci_create(struct gsm_mux *mux,
+		    struct device *uart,
+		    int dlci_address,
+		    gsm_mux_dlci_created_cb_t dlci_created_cb,
+		    void *user_data,
+		    struct gsm_dlci **dlci);
+int gsm_dlci_send(struct gsm_dlci *dlci, const u8_t *buf, size_t size);
+int gsm_dlci_id(struct gsm_dlci *dlci);