Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted

Pull I3C updates from Alexandre Belloni:
 "A new driver this cycle, for the AMD AXI I3C controller.

  There are also new features such as IBI wakeup support, SETAASA device
  discovery and ACPI support for the the DAA methods, meaning we can now
  communicate with the SPD devices on DDR5 modules.

  New driver:
   - AMD AXI I3C master controller

  Subsystem:
   - I3C Common Command Code (CCC) handling improvements, especially
     around GET CCCs
   - SETAASA device discovery support
   - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as
     well as I2C devices on I3C bus
   - IBI-based wakeup support

  Drivers:
   - dw: SETAASA support
   - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C
     controller support, PIO queue management support for HCI v1.2
   - renesas: improve suspend to RAM support, add runtime PM support"

* tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits)
  i3c: dw: reduce do_daa time if there's no client
  i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller
  i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2
  i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode
  i3c: dw: rename "pclk" to "apb" to match dt-binding
  i3c: dw: make struct dw_i3c_cmd smaller
  i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding
  i3c: renesas: Don't register devices when ENTDAA times out
  i3c: master: dw-i3c-master: fix OD timing for first broadcast
  i3c: mipi-i3c-hci: Advertise IBI wakeup capability
  i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev()
  i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI
  i3c: master: Reject IBI requests from non-IBI-capable devices
  i3c: master: Add helper to query bus wakeup requirements
  i3c: master: Report wakeup events for IBIs
  i3c: master: Support IBI-based wakeup capability
  i3c: master: Fix potential UAF in i3c_device_match()
  i3c: master: Fix potential UAF in i3c_device_uevent()
  i3c: Make dev->desc locking assumptions explicit
  i3c: master: Fix use-after-free of master->this
  ...

1 files changed, 147 insertions, 0 deletions

diff --git a/Documentation/admin-guide/serial-console.rst b/Documentation/admin-guide/serial-console.rst
new file mode 100644
index 000000000..1609e7479
--- /dev/null
+++ b/Documentation/admin-guide/serial-console.rst
@@ -0,0 +1,147 @@
+.. _serial_console:
+
+Linux Serial Console
+====================
+
+To use a serial port as console you need to compile the support into your
+kernel - by default it is not compiled in. For PC style serial ports
+it's the config option next to menu option:
+
+:menuselection:`Character devices --> Serial drivers --> 8250/16550 and compatible serial support --> Console on 8250/16550 and compatible serial port`
+
+You must compile serial support into the kernel and not as a module.
+
+It is possible to specify multiple devices for console output. You can
+define a new kernel command line option to select which device(s) to
+use for console output.
+
+The format of this option is::
+
+	console=device,options
+
+	device:		tty0 for the foreground virtual console
+			ttyX for any other virtual console
+			ttySx for a serial port
+			lp0 for the first parallel port
+			ttyUSB0 for the first USB serial device
+
+	options:	depend on the driver. For the serial port this
+			defines the baudrate/parity/bits/flow control of
+			the port, in the format BBBBPNF, where BBBB is the
+			speed, P is parity (n/o/e), N is number of bits,
+			and F is flow control ('r' for RTS). Default is
+			9600n8. The maximum baudrate is 115200.
+
+You can specify multiple console= options on the kernel command line.
+
+The behavior is well defined when each device type is mentioned only once.
+In this case, the output will appear on all requested consoles. And
+the last device will be used when you open ``/dev/console``.
+So, for example::
+
+	console=ttyS1,9600 console=tty0
+
+defines that opening ``/dev/console`` will get you the current foreground
+virtual console, and kernel messages will appear on both the VGA
+console and the 2nd serial port (ttyS1 or COM2) at 9600 baud.
+
+The behavior is more complicated when the same device type is defined more
+times. In this case, there are the following two rules:
+
+1. The output will appear only on the first device of each defined type.
+
+2. ``/dev/console`` will be associated with the first registered device.
+   Where the registration order depends on how kernel initializes various
+   subsystems.
+
+   This rule is used also when the last console= parameter is not used
+   for other reasons. For example, because of a typo or because
+   the hardware is not available.
+
+The result might be surprising. For example, the following two command
+lines have the same result::
+
+	console=ttyS1,9600 console=tty0 console=tty1
+	console=tty0 console=ttyS1,9600 console=tty1
+
+The kernel messages are printed only on ``tty0`` and ``ttyS1``. And
+``/dev/console`` gets associated with ``tty0``. It is because kernel
+tries to register graphical consoles before serial ones. It does it
+because of the default behavior when no console device is specified,
+see below.
+
+Note that the last ``console=tty1`` parameter still makes a difference.
+The kernel command line is used also by systemd. It would use the last
+defined ``tty1`` as the login console.
+
+If no console device is specified, the first device found capable of
+acting as a system console will be used. At this time, the system
+first looks for a VGA card and then for a serial port. So if you don't
+have a VGA card in your system the first serial port will automatically
+become the console, unless the kernel is configured with the
+CONFIG_NULL_TTY_DEFAULT_CONSOLE option, then it will default to using the
+ttynull device.
+
+You will need to create a new device to use ``/dev/console``. The official
+``/dev/console`` is now character device 5,1.
+
+(You can also use a network device as a console.  See
+``Documentation/networking/netconsole.rst`` for information on that.)
+
+Here's an example that will use ``/dev/ttyS1`` (COM2) as the console.
+Replace the sample values as needed.
+
+1. Create ``/dev/console`` (real console) and ``/dev/tty0`` (master virtual
+   console)::
+
+     cd /dev
+     rm -f console tty0
+     mknod -m 622 console c 5 1
+     mknod -m 622 tty0 c 4 0
+
+2. LILO can also take input from a serial device. This is a very
+   useful option. To tell LILO to use the serial port:
+   In lilo.conf (global section)::
+
+     serial  = 1,9600n8 (ttyS1, 9600 bd, no parity, 8 bits)
+
+3. Adjust to kernel flags for the new kernel,
+   again in lilo.conf (kernel section)::
+
+     append = "console=ttyS1,9600"
+
+4. Make sure a getty runs on the serial port so that you can login to
+   it once the system is done booting. This is done by adding a line
+   like this to ``/etc/inittab`` (exact syntax depends on your getty)::
+
+     S1:23:respawn:/sbin/getty -L ttyS1 9600 vt100
+
+5. Init and ``/etc/ioctl.save``
+
+   Sysvinit remembers its stty settings in a file in ``/etc``, called
+   ``/etc/ioctl.save``. REMOVE THIS FILE before using the serial
+   console for the first time, because otherwise init will probably
+   set the baudrate to 38400 (baudrate of the virtual console).
+
+6. ``/dev/console`` and X
+   Programs that want to do something with the virtual console usually
+   open ``/dev/console``. If you have created the new ``/dev/console`` device,
+   and your console is NOT the virtual console some programs will fail.
+   Those are programs that want to access the VT interface, and use
+   ``/dev/console instead of /dev/tty0``. Some of those programs are::
+
+     Xfree86, svgalib, gpm, SVGATextMode
+
+   It should be fixed in modern versions of these programs though.
+
+   Note that if you boot without a ``console=`` option (or with
+   ``console=/dev/tty0``), ``/dev/console`` is the same as ``/dev/tty0``.
+   In that case everything will still work.
+
+7. Thanks
+
+   Thanks to Geert Uytterhoeven <geert@linux-m68k.org>
+   for porting the patches from 2.1.4x to 2.1.6x for taking care of
+   the integration of these patches into m68k, ppc and alpha.
+
+Miquel van Smoorenburg <miquels@cistron.nl>, 11-Jun-2000