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Commit ca782f16 authored by Peter Hurley's avatar Peter Hurley Committed by Greg Kroah-Hartman
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earlycon: 8250: Document kernel command line options 



Document the expected behavior of kernel command lines of the forms:
    console=uart[8250],io|mmio|mmio32,<addr>[,options]
    console=uart[8250],<addr>[,options]
and
    earlycon=uart[8250],io|mmio|mmio32,<addr>[,options]
    earlycon=uart[8250],<addr>[,options]

Signed-off-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 87515772

Documentation/kernel-parameters.txt

+15 −3
Original line number Diff line number Diff line
@@ -713,10 +713,18 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 


		uart[8250],io,<addr>[,options]

		uart[8250],mmio,<addr>[,options]

		uart[8250],mmio32,<addr>[,options]

		uart[8250],0x<addr>[,options]

			Start an early, polled-mode console on the 8250/16550

			UART at the specified I/O port or MMIO address,

			switching to the matching ttyS device later.  The

			options are the same as for ttyS, above.

			switching to the matching ttyS device later.

			MMIO inter-register address stride is either 8-bit

			(mmio) or 32-bit (mmio32).

			If none of [io|mmio|mmio32], <addr> is assumed to be

			equivalent to 'mmio'. 'options' are specified in the

			same format described for ttyS above; if unspecified,

			the h/w is not re-initialized.



		hvc<n>	Use the hypervisor console device <n>. This is for

			both Xen and PowerPC hypervisors.
@@ -944,11 +952,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 
		uart[8250],io,<addr>[,options]

		uart[8250],mmio,<addr>[,options]

		uart[8250],mmio32,<addr>[,options]

		uart[8250],0x<addr>[,options]

			Start an early, polled-mode console on the 8250/16550

			UART at the specified I/O port or MMIO address.

			MMIO inter-register address stride is either 8-bit

			(mmio) or 32-bit (mmio32).

			The options are the same as for ttyS, above.

			If none of [io|mmio|mmio32], <addr> is assumed to be

			equivalent to 'mmio'. 'options' are specified in the

			same format described for "console=ttyS<n>"; if

			unspecified, the h/w is not initialized.



		pl011,<addr>

			Start an early, polled-mode console on a pl011 serial

drivers/tty/serial/8250/8250_core.c

+3 −2
Original line number Diff line number Diff line
@@ -3471,12 +3471,13 @@ static int univ8250_console_setup(struct console *co, char *options) 
 *	@options: ptr to option string from console command line

 *

 *	Only attempts to match console command lines of the form:

 *	    console=uart<>,io|mmio|mmio32,<addr>,<options>

 *	    console=uart<>,<addr>,options

 *	    console=uart[8250],io|mmio|mmio32,<addr>[,<options>]

 *	    console=uart[8250],0x<addr>[,<options>]

 *	This form is used to register an initial earlycon boot console and

 *	replace it with the serial8250_console at 8250 driver init.

 *

 *	Performs console setup for a match (as required by interface)

 *	If no <options> are specified, then assume the h/w is already setup.

 *

 *	Returns 0 if console matches; otherwise non-zero to use default matching

 */