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);
device->con->write = early_serial8250_write;
return 0;
--
2.2.2
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