earlycon: 8250: Document kernel command line options
Subsystems (2)
PATCH 1/1 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 Peter Hurley <[email protected]>
--- Documentation/kernel-parameters.txt | 18 +++++++++++++++--- drivers/tty/serial/8250/8250_core.c | 5 +++-- 2 files changed, 18 insertions(+), 5 deletions(-)
Documentation/kernel-parameters.txt +15 -3
@@ -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
@@ -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 */
Signature · 1 line
2.3.5