Hi Peter,
Am 08.02.2016 um 05:22 schrieb Peter Hurley:
> On 02/07/2016 12:57 PM, Andreas Färber wrote:
>> Reuse the existing console write implementation for implementing
>> DT-based and command-line-based earlycon support.
>>
>> Signed-off-by: Andreas Färber <afaerber@xxxxxxx>
>> ---
>> Documentation/kernel-parameters.txt | 6 ++++++
>> drivers/tty/serial/meson_uart.c | 13 +++++++++++++
>> 2 files changed, 19 insertions(+)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 602065c..90801ac 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -1030,6 +1030,12 @@ Such letter suffixes can also be entirely omitted.
>> the driver will use only 32-bit accessors to read/write
>> the device registers.
>>
>> + meson_serial,<addr>
>> + Start an early, polled-mode console on a meson serial
>> + port at the specified address. The serial port must
>> + already be setup and configured. Options are not yet
>> + supported.
>> +
>> msm_serial,<addr>
>> Start an early, polled-mode console on an msm serial
>> port at the specified address. The serial port
>> diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
>> index b12a37b..6f89567 100644
>> --- a/drivers/tty/serial/meson_uart.c
>> +++ b/drivers/tty/serial/meson_uart.c
>> @@ -548,6 +548,19 @@ static int __init meson_serial_console_init(void)
>> }
>> console_initcall(meson_serial_console_init);
>>
>> +static int __init
>> +meson_serial_early_console_setup(struct earlycon_device *device, const char *opt)
>> +{
>> + if (!device->port.membase)
>> + return -ENODEV;
>> +
>> + device->con->write = meson_serial_console_write;
>
> meson_serial_console_write() is not appropriate for earlycon; it assumes the
> earlycon port is the same as the driver port (it isn't).
Thanks for spotting that.
I forgot to mention that I tested this on arm64, where there is no
earlyprintk any more, seemingly successfully getting a bootconsole
uart0. Using co->data instead of co->index I now get meson_serial0
instead, doh.
This probably slipped though because another patch is necessary for
fixing the baudrate calculation on my device.
>> + return 0;
>> +}
>> +EARLYCON_DECLARE(meson_serial, meson_serial_early_console_setup);
>> +OF_EARLYCON_DECLARE(meson_serial, "amlogic,meson-uart",
>> + meson_serial_early_console_setup);
>
> With today's linux-next (or Greg's tty-next tree), it is no longer necessary to
> declare separate earlycon's when you want both; OF_EARLYCON_DECLARE() declares
> both a devicetree-enabled earlycon and automatically provides for a command line
> earlycon of the same name.
Thanks for the hint, it was based on linux-next from a couple days ago.
Is there any guidance wrt naming? I noticed that msm uses -uart in the
compatible string and _serial for earlycon, so I copied that; should it
rather be meson_uart or just meson?
Regards,
Andreas
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