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.
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);
--
1.9.1
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