Earlycon matching can only be triggered if 'earlycon=...' has been
specified on the kernel command line. To workaround this limitation
requires tight coupling between arches and specific serial drivers
in order to start an earlycon. Devicetree avoids this limitation
with a link table that contains the required data to match earlycons.

Mirror this approach for earlycon match by name. Re-purpose
EARLYCON_DECLARE to generate a table entry which associates name with
setup() function. Re-purpose setup_earlycon() to scan this table for
an earlycon match, which is registered if found.

Declare one "earlycon" early_param, which calls setup_earlycon().

This design allows setup_earlycon() to be called directly with a
param string (as if 'earlycon=...' had been set on the command line).
Re-registration (either directly or by early_param) is prevented.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Separate earlycon matching from registration; add register_earlycon
which initializes and registers the matched earlycon.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Earlycon param strings of the form
   earlycon=<name>
are rejected from parse_options() with an error (which, in turn,
results in a NULL argument for the setup() method options parameter).

Only pass non-empty string to parse_options(); this will enable
handling actual parse errors differently than expected and allow
formats.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Because setup_earlycon() continues to attempt console registration
if an error occurred parsing the option string, the actual value of
the error code from parse_options() is ignored.
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Initializing the ->uartclk field is not related to option parsing;
relocate from parse_options() to setup_earlycon() (which mirrors the
behavior of of_setup_earlycon()).
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Prepare to support console-defined matching; refactor the command
line parameter string processing from parse_options() into a
new core function, uart_parse_earlycon(), which decodes command line
parameters of the form:
   earlycon=<name>,io|mmio|mmio32,<addr>,<options>
   console=<name>,io|mmio|mmio32,<addr>,<options>
   earlycon=<name>,0x<addr>,<options>
   console=<name>,0x<addr>,<options>
Signed-off-by: NPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

For the case in which we just provide an address as an argument to the
earlycon console type like:

earlycon=msm_serial_dm,0xf991e000

We would report this as an IO port based mapping and not as MMIO.  Simple
fix to use the port->iotype to decide which message to print.
Signed-off-by: NKumar Gala <galak@codeaurora.org>
Acked-by: NMark RUtland <mark.rutland@arm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

In the conversion to generic early console, the passing of options from
the early 8250 console to the regular ttyS console was broken. This
resulted in the baud rate changing when switching consoles during boot.

This feature allows specifying a single console option on the kernel
command line rather than both an early console and regular serial tty
console. It would be nice to generalize this feature. However, it only
works if the correct baud rate can be probed early which is not the
case on many platforms which have non-standard UART clock rates. So for
now, this is left as an 8250 specific feature.
Reported-and-tested-by: NTony Luck <tony.luck@intel.com>
Signed-off-by: NRob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This adds the infrastructure to generic earlycon for earlycon setup
using DT. The actual setup is not enabled until a following commit to
add the FDT parsing.
Signed-off-by: NRob Herring <robh@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: NGrant Likely <grant.likely@linaro.org>

Commit 9aac5887 (tty/serial: add generic serial earlycon) moved
console option parsing from 8250_early.c and converted to kstrto*
functions from simple_strtoul along the way. However, kstrto* functions
are not equivalent in that they do not allow non-convertible characters
at the end such as "115200n8". Fix this by changing back to
simple_strtoul and ignore what checkpatch.pl says.
Reported-by: NYinghai Lu <yinghai@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: linux-serial@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This introduces generic earlycon infrastructure for serial devices
based on the 8250 earlycon. This allows for supporting earlycon option
with other serial devices. The earlycon output is enabled at the time
early_params are processed.

Only architectures that have fixmap support or have functional ioremap
when early_params are processed are supported. This is the same
restriction that the 8250 driver had.
Signed-off-by: NRob Herring <robh@kernel.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>