Messages in this thread Patch in this message | | | Date | Sun, 01 Feb 2015 13:26:33 -0500 | From | Peter Hurley <> | Subject | Re: [PATCH v2 1/4] tty: serial: Add 8250 earlycon to support noinit option |
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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@hurleysoftware.com> 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@hurleysoftware.com> --- 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); device->con->write = early_serial8250_write; return 0; -- 2.2.2
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