Merge tag 'tty-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty and serial driver updates from Greg KH:
 "Here is the big set of tty and serial driver updates for 5.19-rc1.

  Lots of tiny cleanups in here, the major stuff is:

   - termbit cleanups and unification by Ilpo. A much needed change that
     goes a long way to making things simpler for all of the different
     arches

   - tty documentation cleanups and movements to their own place in the
     documentation tree

   - old tty driver cleanups and fixes from Jiri to bring some existing
     drivers into the modern world

   - RS485 cleanups and unifications to make it easier for individual
     drivers to support this mode instead of having to duplicate logic
     in each driver

   - Lots of 8250 driver updates and additions

   - new device id additions

   - n_gsm continued fixes and cleanups

   - other minor serial driver updates and cleanups

  All of these have been in linux-next for weeks with no reported issues"

* tag 'tty-5.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (166 commits)
  tty: Rework receive flow control char logic
  pcmcia: synclink_cs: Don't allow CS5-6
  serial: stm32-usart: Correct CSIZE, bits, and parity
  serial: st-asc: Sanitize CSIZE and correct PARENB for CS7
  serial: sifive: Sanitize CSIZE and c_iflag
  serial: sh-sci: Don't allow CS5-6
  serial: txx9: Don't allow CS5-6
  serial: rda-uart: Don't allow CS5-6
  serial: digicolor-usart: Don't allow CS5-6
  serial: uartlite: Fix BRKINT clearing
  serial: cpm_uart: Fix build error without CONFIG_SERIAL_CPM_CONSOLE
  serial: core: Do stop_rx in suspend path for console if console_suspend is disabled
  tty: serial: qcom-geni-serial: Remove uart frequency table. Instead, find suitable frequency with call to clk_round_rate.
  dt-bindings: serial: renesas,em-uart: Add RZ/V2M clock to access the registers
  serial: 8250_fintek: Check SER_RS485_RTS_* only with RS485
  Revert "serial: 8250_mtk: Make sure to select the right FEATURE_SEL"
  serial: msm_serial: disable interrupts in __msm_console_write()
  serial: meson: acquire port->lock in startup()
  serial: 8250_dw: Use dev_err_probe()
  serial: 8250_dw: Use devm_add_action_or_reset()
  ...

25 files changed, 466 insertions, 179 deletions

diff --git a/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml b/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml
index ff364bd0fbac..30eaa62e1aed 100644
--- a/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml
+++ b/Documentation/devicetree/bindings/serial/fsl-lpuart.yaml
@@ -23,7 +23,9 @@ properties:
           - fsl,imx8qxp-lpuart
           - fsl,imxrt1050-lpuart
       - items:
-          - const: fsl,imx8ulp-lpuart
+          - enum:
+              - fsl,imx93-lpuart
+              - fsl,imx8ulp-lpuart
           - const: fsl,imx7ulp-lpuart
       - items:
           - enum:
diff --git a/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml b/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
new file mode 100644
index 000000000000..05a6999808d1
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
@@ -0,0 +1,86 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/serial/qcom,serial-geni-qcom.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Qualcomm Geni based QUP UART interface
+
+maintainers:
+  - Andy Gross <agross@kernel.org>
+  - Bjorn Andersson <bjorn.andersson@linaro.org>
+
+allOf:
+  - $ref: /schemas/serial/serial.yaml#
+
+properties:
+  compatible:
+    enum:
+      - qcom,geni-uart
+      - qcom,geni-debug-uart
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: se
+
+  interconnects:
+    maxItems: 2
+
+  interconnect-names:
+    items:
+      - const: qup-core
+      - const: qup-config
+
+  interrupts:
+    minItems: 1
+    items:
+      - description: UART core irq
+      - description: Wakeup irq (RX GPIO)
+
+  operating-points-v2: true
+
+  pinctrl-0: true
+  pinctrl-1: true
+
+  pinctrl-names:
+    minItems: 1
+    items:
+      - const: default
+      - const: sleep
+
+  power-domains:
+    maxItems: 1
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - clocks
+  - clock-names
+  - interrupts
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/qcom,gcc-sc7180.h>
+    #include <dt-bindings/interconnect/qcom,sc7180.h>
+
+    serial@a88000 {
+        compatible = "qcom,geni-uart";
+        reg = <0xa88000 0x7000>;
+        interrupts = <GIC_SPI 355 IRQ_TYPE_LEVEL_HIGH>;
+        clock-names = "se";
+        clocks = <&gcc GCC_QUPV3_WRAP0_S0_CLK>;
+        pinctrl-0 = <&qup_uart0_default>;
+        pinctrl-names = "default";
+        interconnects = <&qup_virt MASTER_QUP_CORE_0 0 &qup_virt SLAVE_QUP_CORE_0 0>,
+                        <&gem_noc MASTER_APPSS_PROC 0 &config_noc SLAVE_QUP_0 0>;
+        interconnect-names = "qup-core", "qup-config";
+    };
+...
diff --git a/Documentation/devicetree/bindings/serial/renesas,em-uart.yaml b/Documentation/devicetree/bindings/serial/renesas,em-uart.yaml
index e98ec48fee46..b25aca733b72 100644
--- a/Documentation/devicetree/bindings/serial/renesas,em-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/renesas,em-uart.yaml
@@ -9,12 +9,16 @@ title: Renesas EMMA Mobile UART Interface
 maintainers:
   - Magnus Damm <magnus.damm@gmail.com>
 
-allOf:
-  - $ref: serial.yaml#
-
 properties:
   compatible:
-    const: renesas,em-uart
+    oneOf:
+      - items:
+          - enum:
+              - renesas,r9a09g011-uart    # RZ/V2M
+          - const: renesas,em-uart        # generic EMMA Mobile compatible UART
+
+      - items:
+          - const: renesas,em-uart        # generic EMMA Mobile compatible UART
 
   reg:
     maxItems: 1
@@ -23,10 +27,31 @@ properties:
     maxItems: 1
 
   clocks:
-    maxItems: 1
+    minItems: 1
+    items:
+      - description: UART functional clock
+      - description: Internal clock to access the registers
 
   clock-names:
-    const: sclk
+    minItems: 1
+    items:
+      - const: sclk
+      - const: pclk
+
+allOf:
+  - $ref: serial.yaml#
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: renesas,r9a09g011-uart
+    then:
+      properties:
+        clocks:
+          minItems: 2
+        clock-names:
+          minItems: 2
 
 required:
   - compatible
diff --git a/Documentation/devicetree/bindings/serial/renesas,hscif.yaml b/Documentation/devicetree/bindings/serial/renesas,hscif.yaml
index ee9804cd49bb..87180d95cd4c 100644
--- a/Documentation/devicetree/bindings/serial/renesas,hscif.yaml
+++ b/Documentation/devicetree/bindings/serial/renesas,hscif.yaml
@@ -51,10 +51,16 @@ properties:
               - renesas,hscif-r8a77980     # R-Car V3H
               - renesas,hscif-r8a77990     # R-Car E3
               - renesas,hscif-r8a77995     # R-Car D3
-              - renesas,hscif-r8a779a0     # R-Car V3U
           - const: renesas,rcar-gen3-hscif # R-Car Gen3 and RZ/G2
           - const: renesas,hscif           # generic HSCIF compatible UART
 
+      - items:
+          - enum:
+              - renesas,hscif-r8a779a0     # R-Car V3U
+              - renesas,hscif-r8a779g0     # R-Car V4H
+          - const: renesas,rcar-gen4-hscif # R-Car Gen4
+          - const: renesas,hscif           # generic HSCIF compatible UART
+
   reg:
     maxItems: 1
 
@@ -113,6 +119,7 @@ if:
         enum:
           - renesas,rcar-gen2-hscif
           - renesas,rcar-gen3-hscif
+          - renesas,rcar-gen4-hscif
 then:
   required:
     - resets
diff --git a/Documentation/devicetree/bindings/serial/renesas,scif.yaml b/Documentation/devicetree/bindings/serial/renesas,scif.yaml
index 5d37f8f189fb..90fe45265fbc 100644
--- a/Documentation/devicetree/bindings/serial/renesas,scif.yaml
+++ b/Documentation/devicetree/bindings/serial/renesas,scif.yaml
@@ -60,12 +60,12 @@ properties:
               - renesas,scif-r8a77980     # R-Car V3H
               - renesas,scif-r8a77990     # R-Car E3
               - renesas,scif-r8a77995     # R-Car D3
-              - renesas,scif-r8a779a0     # R-Car V3U
           - const: renesas,rcar-gen3-scif # R-Car Gen3 and RZ/G2
           - const: renesas,scif           # generic SCIF compatible UART
 
       - items:
           - enum:
+              - renesas,scif-r8a779a0     # R-Car V3U
               - renesas,scif-r8a779f0     # R-Car S4-8
           - const: renesas,rcar-gen4-scif # R-Car Gen4
           - const: renesas,scif           # generic SCIF compatible UART
diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml
index 0c9fa694f85c..f2c9c9fe6aa7 100644
--- a/Documentation/devicetree/bindings/serial/rs485.yaml
+++ b/Documentation/devicetree/bindings/serial/rs485.yaml
@@ -33,6 +33,11 @@ properties:
     description: drive RTS low when sending (default is high).
     $ref: /schemas/types.yaml#/definitions/flag
 
+  rs485-rx-active-high:
+    description: Polarity of receiver enable signal (when separate from RTS).
+      True indicates active high (default is low).
+    $ref: /schemas/types.yaml#/definitions/flag
+
   linux,rs485-enabled-at-boot-time:
     description: enables the rs485 feature at boot time. It can be disabled
       later with proper ioctl.
diff --git a/Documentation/devicetree/bindings/serial/socionext,uniphier-uart.yaml b/Documentation/devicetree/bindings/serial/socionext,uniphier-uart.yaml
index d490c7c4b967..3d01cc355778 100644
--- a/Documentation/devicetree/bindings/serial/socionext,uniphier-uart.yaml
+++ b/Documentation/devicetree/bindings/serial/socionext,uniphier-uart.yaml
@@ -20,7 +20,10 @@ properties:
     maxItems: 1
 
   clocks:
-    minItems: 1
+    maxItems: 1
+
+  resets:
+    maxItems: 1
 
   auto-flow-control:
     description: enable automatic flow control support.
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index a7b0223e2886..d76a60d95b58 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -101,6 +101,7 @@ available subsections can be seen below.
    surface_aggregator/index
    switchtec
    sync_file
+   tty/index
    vfio-mediated-device
    vfio
    vfio-pci-device-specific-driver-acceptance
diff --git a/Documentation/driver-api/serial/driver.rst b/Documentation/driver-api/serial/driver.rst
index 06ec04ba086f..7ef83fd3917b 100644
--- a/Documentation/driver-api/serial/driver.rst
+++ b/Documentation/driver-api/serial/driver.rst
@@ -311,7 +311,7 @@ hardware.
 	This call must not sleep
 
   set_ldisc(port,termios)
-	Notifier for discipline change. See Documentation/tty/tty_ldisc.rst.
+	Notifier for discipline change. See ../tty/tty_ldisc.rst.
 
 	Locking: caller holds tty_port->mutex
 
diff --git a/Documentation/driver-api/serial/index.rst b/Documentation/driver-api/serial/index.rst
index 7eb21a695fc3..03a55b987a1d 100644
--- a/Documentation/driver-api/serial/index.rst
+++ b/Documentation/driver-api/serial/index.rst
@@ -16,8 +16,6 @@ Serial drivers
 .. toctree::
     :maxdepth: 1
 
-    moxa-smartio
-    n_gsm
     serial-iso7816
     serial-rs485
 
diff --git a/Documentation/driver-api/serial/n_gsm.rst b/Documentation/driver-api/serial/n_gsm.rst
deleted file mode 100644
index 49956509ad73..000000000000
--- a/Documentation/driver-api/serial/n_gsm.rst
+++ /dev/null
@@ -1,159 +0,0 @@
-==============================
-GSM 0710 tty multiplexor HOWTO
-==============================
-
-This line discipline implements the GSM 07.10 multiplexing protocol
-detailed in the following 3GPP document:
-
-	https://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip
-
-This document give some hints on how to use this driver with GPRS and 3G
-modems connected to a physical serial port.
-
-How to use it
--------------
-1. config initiator
-^^^^^^^^^^^^^^^^^^^^^
-
-1.1 initialize the modem in 0710 mux mode (usually AT+CMUX= command) through
-    its serial port. Depending on the modem used, you can pass more or less
-    parameters to this command.
-
-1.2 switch the serial line to using the n_gsm line discipline by using
-    TIOCSETD ioctl.
-
-1.3 configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl.
-
-1.4 obtain base gsmtty number for the used serial port.
-
-Major parts of the initialization program :
-(a good starting point is util-linux-ng/sys-utils/ldattach.c)::
-
-  #include <stdio.h>
-  #include <stdint.h>
-  #include <linux/gsmmux.h>
-  #include <linux/tty.h>
-  #define DEFAULT_SPEED	B115200
-  #define SERIAL_PORT	/dev/ttyS0
-
-	int ldisc = N_GSM0710;
-	struct gsm_config c;
-	struct termios configuration;
-	uint32_t first;
-
-	/* open the serial port connected to the modem */
-	fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
-
-	/* configure the serial port : speed, flow control ... */
-
-	/* send the AT commands to switch the modem to CMUX mode
-	   and check that it's successful (should return OK) */
-	write(fd, "AT+CMUX=0\r", 10);
-
-	/* experience showed that some modems need some time before
-	   being able to answer to the first MUX packet so a delay
-	   may be needed here in some case */
-	sleep(3);
-
-	/* use n_gsm line discipline */
-	ioctl(fd, TIOCSETD, &ldisc);
-
-	/* get n_gsm configuration */
-	ioctl(fd, GSMIOC_GETCONF, &c);
-	/* we are initiator and need encoding 0 (basic) */
-	c.initiator = 1;
-	c.encapsulation = 0;
-	/* our modem defaults to a maximum size of 127 bytes */
-	c.mru = 127;
-	c.mtu = 127;
-	/* set the new configuration */
-	ioctl(fd, GSMIOC_SETCONF, &c);
-	/* get first gsmtty device node */
-	ioctl(fd, GSMIOC_GETFIRST, &first);
-	printf("first muxed line: /dev/gsmtty%i\n", first);
-
-	/* and wait for ever to keep the line discipline enabled */
-	daemon(0,0);
-	pause();
-
-1.5 use these devices as plain serial ports.
-
-   for example, it's possible:
-
-   - and to use gnokii to send / receive SMS on ttygsm1
-   - to use ppp to establish a datalink on ttygsm2
-
-1.6 first close all virtual ports before closing the physical port.
-
-   Note that after closing the physical port the modem is still in multiplexing
-   mode. This may prevent a successful re-opening of the port later. To avoid
-   this situation either reset the modem if your hardware allows that or send
-   a disconnect command frame manually before initializing the multiplexing mode
-   for the second time. The byte sequence for the disconnect command frame is::
-
-      0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9.
-
-2. config requester
-^^^^^^^^^^^^^^^^^^^^^
-
-2.1 receive string "AT+CMUX= command" through its serial port,initialize
-    mux mode config
-
-2.2 switch the serial line to using the n_gsm line discipline by using
-    TIOCSETD ioctl.
-
-2.3 configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl.
-
-2.4 obtain base gsmtty number for the used serial port::
-
-  #include <stdio.h>
-  #include <stdint.h>
-  #include <linux/gsmmux.h>
-  #include <linux/tty.h>
-  #define DEFAULT_SPEED	B115200
-  #define SERIAL_PORT	/dev/ttyS0
-
-	int ldisc = N_GSM0710;
-	struct gsm_config c;
-	struct termios configuration;
-	uint32_t first;
-
-	/* open the serial port */
-	fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
-
-	/* configure the serial port : speed, flow control ... */
-
-	/* get serial data and check "AT+CMUX=command" parameter ... */
-
-	/* use n_gsm line discipline */
-	ioctl(fd, TIOCSETD, &ldisc);
-
-	/* get n_gsm configuration */
-	ioctl(fd, GSMIOC_GETCONF, &c);
-	/* we are requester and need encoding 0 (basic) */
-	c.initiator = 0;
-	c.encapsulation = 0;
-	/* our modem defaults to a maximum size of 127 bytes */
-	c.mru = 127;
-	c.mtu = 127;
-	/* set the new configuration */
-	ioctl(fd, GSMIOC_SETCONF, &c);
-	/* get first gsmtty device node */
-	ioctl(fd, GSMIOC_GETFIRST, &first);
-	printf("first muxed line: /dev/gsmtty%i\n", first);
-
-	/* and wait for ever to keep the line discipline enabled */
-	daemon(0,0);
-	pause();
-
-Additional Documentation
-------------------------
-More practical details on the protocol and how it's supported by industrial
-modems can be found in the following documents :
-
-- http://www.telit.com/module/infopool/download.php?id=616
-- http://www.u-blox.com/images/downloads/Product_Docs/LEON-G100-G200-MuxImplementation_ApplicationNote_%28GSM%20G1-CS-10002%29.pdf
-- http://www.sierrawireless.com/Support/Downloads/AirPrime/WMP_Series/~/media/Support_Downloads/AirPrime/Application_notes/CMUX_Feature_Application_Note-Rev004.ashx
-- http://wm.sim.com/sim/News/photo/2010721161442.pdf
-
-11-03-08 - Eric Bénard - <eric@eukrea.com>
diff --git a/Documentation/tty/index.rst b/Documentation/driver-api/tty/index.rst
index 21ea0cb21e55..2d32606a4278 100644
--- a/Documentation/tty/index.rst
+++ b/Documentation/driver-api/tty/index.rst
@@ -36,18 +36,16 @@ In-detail description of the named TTY structures is in separate documents:
    tty_struct
    tty_ldisc
    tty_buffer
-   n_tty
    tty_internals
 
 Writing TTY Driver
 ==================
 
 Before one starts writing a TTY driver, they must consider
-:doc:`Serial <../driver-api/serial/driver>` and :doc:`USB Serial
-<../usb/usb-serial>` layers
-first. Drivers for serial devices can often use one of these specific layers to
-implement a serial driver. Only special devices should be handled directly by
-the TTY Layer. If you are about to write such a driver, read on.
+:doc:`Serial <../serial/driver>` and :doc:`USB Serial <../../usb/usb-serial>`
+layers first. Drivers for serial devices can often use one of these specific
+layers to implement a serial driver. Only special devices should be handled
+directly by the TTY Layer. If you are about to write such a driver, read on.
 
 A *typical* sequence a TTY driver performs is as follows:
 
@@ -61,3 +59,15 @@ A *typical* sequence a TTY driver performs is as follows:
 Steps regarding driver, i.e. 1., 3., and 5. are described in detail in
 :doc:`tty_driver`. For the other two (devices handling), look into
 :doc:`tty_port`.
+
+Other Documentation
+===================
+
+Miscellaneous documentation can be further found in these documents:
+
+.. toctree::
+   :maxdepth: 2
+
+   moxa-smartio
+   n_gsm
+   n_tty
diff --git a/Documentation/driver-api/serial/moxa-smartio.rst b/Documentation/driver-api/tty/moxa-smartio.rst
index af25bc5cc3e6..af25bc5cc3e6 100644
--- a/Documentation/driver-api/serial/moxa-smartio.rst
+++ b/Documentation/driver-api/tty/moxa-smartio.rst
diff --git a/Documentation/driver-api/tty/n_gsm.rst b/Documentation/driver-api/tty/n_gsm.rst
new file mode 100644
index 000000000000..35d7381515b0
--- /dev/null
+++ b/Documentation/driver-api/tty/n_gsm.rst
@@ -0,0 +1,153 @@
+==============================
+GSM 0710 tty multiplexor HOWTO
+==============================
+
+.. contents:: :local:
+
+This line discipline implements the GSM 07.10 multiplexing protocol
+detailed in the following 3GPP document:
+
+	https://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip
+
+This document give some hints on how to use this driver with GPRS and 3G
+modems connected to a physical serial port.
+
+How to use it
+=============
+
+Config Initiator
+----------------
+
+#. Initialize the modem in 0710 mux mode (usually ``AT+CMUX=`` command) through
+   its serial port. Depending on the modem used, you can pass more or less
+   parameters to this command.
+
+#. Switch the serial line to using the n_gsm line discipline by using
+   ``TIOCSETD`` ioctl.
+
+#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.
+
+#. Obtain base gsmtty number for the used serial port.
+
+   Major parts of the initialization program
+   (a good starting point is util-linux-ng/sys-utils/ldattach.c)::
+
+      #include <stdio.h>
+      #include <stdint.h>
+      #include <linux/gsmmux.h>
+      #include <linux/tty.h>
+
+      #define DEFAULT_SPEED	B115200
+      #define SERIAL_PORT	/dev/ttyS0
+
+      int ldisc = N_GSM0710;
+      struct gsm_config c;
+      struct termios configuration;
+      uint32_t first;
+
+      /* open the serial port connected to the modem */
+      fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
+
+      /* configure the serial port : speed, flow control ... */
+
+      /* send the AT commands to switch the modem to CMUX mode
+         and check that it's successful (should return OK) */
+      write(fd, "AT+CMUX=0\r", 10);
+
+      /* experience showed that some modems need some time before
+         being able to answer to the first MUX packet so a delay
+         may be needed here in some case */
+      sleep(3);
+
+      /* use n_gsm line discipline */
+      ioctl(fd, TIOCSETD, &ldisc);
+
+      /* get n_gsm configuration */
+      ioctl(fd, GSMIOC_GETCONF, &c);
+      /* we are initiator and need encoding 0 (basic) */
+      c.initiator = 1;
+      c.encapsulation = 0;
+      /* our modem defaults to a maximum size of 127 bytes */
+      c.mru = 127;
+      c.mtu = 127;
+      /* set the new configuration */
+      ioctl(fd, GSMIOC_SETCONF, &c);
+      /* get first gsmtty device node */
+      ioctl(fd, GSMIOC_GETFIRST, &first);
+      printf("first muxed line: /dev/gsmtty%i\n", first);
+
+      /* and wait for ever to keep the line discipline enabled */
+      daemon(0,0);
+      pause();
+
+#. Use these devices as plain serial ports.
+
+   For example, it's possible:
+
+   - to use *gnokii* to send / receive SMS on ``ttygsm1``
+   - to use *ppp* to establish a datalink on ``ttygsm2``
+
+#. First close all virtual ports before closing the physical port.
+
+   Note that after closing the physical port the modem is still in multiplexing
+   mode. This may prevent a successful re-opening of the port later. To avoid
+   this situation either reset the modem if your hardware allows that or send
+   a disconnect command frame manually before initializing the multiplexing mode
+   for the second time. The byte sequence for the disconnect command frame is::
+
+      0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9
+
+Config Requester
+----------------
+
+#. Receive ``AT+CMUX=`` command through its serial port, initialize mux mode
+   config.
+
+#. Switch the serial line to using the *n_gsm* line discipline by using
+   ``TIOCSETD`` ioctl.
+
+#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.
+
+#. Obtain base gsmtty number for the used serial port::
+
+        #include <stdio.h>
+        #include <stdint.h>
+        #include <linux/gsmmux.h>
+        #include <linux/tty.h>
+        #define DEFAULT_SPEED	B115200
+        #define SERIAL_PORT	/dev/ttyS0
+
+	int ldisc = N_GSM0710;
+	struct gsm_config c;
+	struct termios configuration;
+	uint32_t first;
+
+	/* open the serial port */
+	fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
+
+	/* configure the serial port : speed, flow control ... */
+
+	/* get serial data and check "AT+CMUX=command" parameter ... */
+
+	/* use n_gsm line discipline */
+	ioctl(fd, TIOCSETD, &ldisc);
+
+	/* get n_gsm configuration */
+	ioctl(fd, GSMIOC_GETCONF, &c);
+	/* we are requester and need encoding 0 (basic) */
+	c.initiator = 0;
+	c.encapsulation = 0;
+	/* our modem defaults to a maximum size of 127 bytes */
+	c.mru = 127;
+	c.mtu = 127;
+	/* set the new configuration */
+	ioctl(fd, GSMIOC_SETCONF, &c);
+	/* get first gsmtty device node */
+	ioctl(fd, GSMIOC_GETFIRST, &first);
+	printf("first muxed line: /dev/gsmtty%i\n", first);
+
+	/* and wait for ever to keep the line discipline enabled */
+	daemon(0,0);
+	pause();
+
+11-03-08 - Eric Bénard - <eric@eukrea.com>
diff --git a/Documentation/tty/n_tty.rst b/Documentation/driver-api/tty/n_tty.rst
index 15b70faee72d..15b70faee72d 100644
--- a/Documentation/tty/n_tty.rst
+++ b/Documentation/driver-api/tty/n_tty.rst
diff --git a/Documentation/tty/tty_buffer.rst b/Documentation/driver-api/tty/tty_buffer.rst
index a39d4781e0d2..a39d4781e0d2 100644
--- a/Documentation/tty/tty_buffer.rst
+++ b/Documentation/driver-api/tty/tty_buffer.rst
diff --git a/Documentation/tty/tty_driver.rst b/Documentation/driver-api/tty/tty_driver.rst
index cc529f863406..cc529f863406 100644
--- a/Documentation/tty/tty_driver.rst
+++ b/Documentation/driver-api/tty/tty_driver.rst
diff --git a/Documentation/tty/tty_internals.rst b/Documentation/driver-api/tty/tty_internals.rst
index d0d415820300..d0d415820300 100644
--- a/Documentation/tty/tty_internals.rst
+++ b/Documentation/driver-api/tty/tty_internals.rst
diff --git a/Documentation/tty/tty_ldisc.rst b/Documentation/driver-api/tty/tty_ldisc.rst
index 5144751be804..5144751be804 100644
--- a/Documentation/tty/tty_ldisc.rst
+++ b/Documentation/driver-api/tty/tty_ldisc.rst
diff --git a/Documentation/tty/tty_port.rst b/Documentation/driver-api/tty/tty_port.rst
index 5cb90e954fcf..5cb90e954fcf 100644
--- a/Documentation/tty/tty_port.rst
+++ b/Documentation/driver-api/tty/tty_port.rst
diff --git a/Documentation/tty/tty_struct.rst b/Documentation/driver-api/tty/tty_struct.rst
index c72f5a4293b2..c72f5a4293b2 100644
--- a/Documentation/tty/tty_struct.rst
+++ b/Documentation/driver-api/tty/tty_struct.rst
diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst
index 6b62425ef9cd..dbb03022b127 100644
--- a/Documentation/firmware-guide/acpi/enumeration.rst
+++ b/Documentation/firmware-guide/acpi/enumeration.rst
@@ -389,6 +389,31 @@ descriptors once the device is released.
 See Documentation/firmware-guide/acpi/gpio-properties.rst for more information
 about the _DSD binding related to GPIOs.
 
+RS-485 support
+==============
+
+ACPI _DSD (Device Specific Data) can be used to describe RS-485 capability