On 02/01/2015 10:16 PM, Eddie Huang wrote: > Hi Peter, > > On Sun, 2015-02-01 at 13:26 -0500, Peter Hurley wrote: >> On 02/01/2015 11:27 AM, Peter Hurley wrote: >>> Hi Eddie, >>> >>> On 01/12/2015 08:08 AM, Eddie Huang wrote: >>>> Add earlycon support not only baudrate option, but also add noinit option. >>>> If use noinit option, 8250 earlycon will not init serial hardware and use >>>> loader setting. >>> >>> I see this went into Greg's tty-testing branch. >>> >>> The only point of this is to not program the divisor, right? >>> >>> I ask because early_serial8250_setup() could already handle this without >>> extra options by simply not doing divisor programming if no baud option is >>> present. >> >> Does the patch below work for your use-case? >> >> [ Note: the patch applies to 3.19-rcX. To test, your noinit patches need to be >> reverted first. >> ] >> >> --- >% --- >> From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> >> Subject: [PATCH] serial: 8250_early: Assume uart already initialized if no >> baud option >> >> The <baud><parity><bit> option string is not supplied if the earlycon >> is started via devicetree and OF_EARLYCON_DECLARE(). The option string >> is also not required if started via kernel command line parameters of >> the form: >> earlycon=uart,mmio,<addr> >> console=uart,mmio,<addr> >> >> If earlycon_device->baud is 0, then an option string was not supplied. >> In this case, assume the uart has already been initialized by the >> bootloader or firmware. >> >> Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx> >> --- >> drivers/tty/serial/8250/8250_early.c | 10 ++++++++-- >> 1 file changed, 8 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/tty/serial/8250/8250_early.c b/drivers/tty/serial/8250/8250_early.c >> index d7b831b..1701d00 100644 >> --- a/drivers/tty/serial/8250/8250_early.c >> +++ b/drivers/tty/serial/8250/8250_early.c >> @@ -149,12 +149,18 @@ static int __init early_serial8250_setup(struct earlycon_device *device, >> return 0; >> >> if (!device->baud) { >> + struct uart_port *port = &device->port; >> + unsigned int ier; >> + >> device->baud = probe_baud(&device->port); >> snprintf(device->options, sizeof(device->options), "%u", >> device->baud); >> - } >> >> - init_port(device); >> + /* assume the device was initialized, only mask interrupts */ >> + ier = serial8250_early_in(port, UART_IER); >> + serial8250_early_out(port, UART_IER, ier & UART_IER_UUE); >> + } else >> + init_port(device); > Should add brace in else. I don't do that unless I have to. > Where is original line here. > early_device = device; Whoops :) I wrote the patch from a private branch which implements extensible console matching (so a console can define its own match function) and a bunch of other console cleanup and code removal. In that series, early_device becomes unnecessary and is removed. I'll respin proper patches on top of Greg's tty-testing branch with reverts for the noinit options. I noticed that one of the noinit patches actually has the linkage for the mtk earlycon, so I'll be sure to preserve that. Regards, Peter Hurley -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html