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
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