On 10/19/2015 11:36 PM, Masahiro Yamada wrote:
> The input clock frequency varies from device to device, but the
> earlycon uses the fixed frequency (BASE_BAUD * 16). It makes
> impossible to set the correct divisor to the register.
So the bootloader hasn't setup the serial port?
> This commit allows to specify the input clock frequency from the
> kernel-parameter.
>
> [Example]
>
> earlycon=uart8250,mmio32,0x43fb0000,115200,12288000
>
> The input clock frequency (12288000, in this case) should be specified
> after the baudrate. If not specified, the default (BASE_BAUD * 16) is
> used.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> ---
>
> Changes in v2: None
>
> drivers/tty/serial/earlycon.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
> index 07f7393..8030765 100644
> --- a/drivers/tty/serial/earlycon.c
> +++ b/drivers/tty/serial/earlycon.c
> @@ -95,6 +95,13 @@ static int __init parse_options(struct earlycon_device *device, char *options)
> length = min(strcspn(options, " ") + 1,
> (size_t)(sizeof(device->options)));
> strlcpy(device->options, options, length);
> + options = strchr(options, ',');
> + if (options) {
> + options++;
> + port->uartclk = simple_strtoul(options, NULL, 0);
> + }
> + if (!port->uartclk)
> + port->uartclk = BASE_BAUD * 16;
> }
>
> if (port->iotype == UPIO_MEM || port->iotype == UPIO_MEM16 ||
> @@ -122,7 +129,6 @@ static int __init register_earlycon(char *buf, const struct earlycon_id *match)
> if (buf && !parse_options(&early_console_dev, buf))
> buf = NULL;
>
> - port->uartclk = BASE_BAUD * 16;
> if (port->mapbase)
> port->membase = earlycon_map(port->mapbase, 64);
>
>
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