On Tue, Oct 14, 2008 at 03:39:44PM -0700, Yinghai Lu wrote:
Good suggestion. Here is a much simpler patch that just expands
the early printk to add a clock frequency parameter, e.g. I use:
console=uart8250,io,0xe880,115200,921600
Signed-off-by: Don Dugger <donald.d.dugger@intel.com>
Documentation/kernel-parameters.txt | 9 ++++++---
drivers/serial/8250_early.c | 5 +++++
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2443f5b..95ab44f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -505,12 +505,15 @@ and is between 256 and 4096 characters. It is defined in the file
Documentation/networking/netconsole.txt for an
alternative.
- uart[8250],io,<addr>[,options]
- uart[8250],mmio,<addr>[,options]
+ uart[8250],io,<addr>[,options[,clk]]
+ uart[8250],mmio,<addr>[,options[,clk]]
Start an early, polled-mode console on the 8250/16550
UART at the specified I/O port or MMIO address,
switching to the matching ttyS device later. The
- options are the same as for ttyS, above.
+ "options" are the same as for ttyS, above. "clk"
+ is the crystal frequency which defaults to 1843200
+ (115200 * 16) but some hardware uses different
+ crystal.
If the device connected to the port is not a TTY but a braille
device, prepend "brl," before the device type, for instance
diff --git a/drivers/serial/8250_early.c b/drivers/serial/8250_early.c
index f279745..edd5803 100644
--- a/drivers/serial/8250_early.c
+++ b/drivers/serial/8250_early.c
@@ -180,6 +180,11 @@ static int __init parse_options(struct early_serial8250_device *device,
snprintf(device->options, sizeof(device->options), "%u",
device->baud);
}
+ options = strchr(options, ',');
+ if (options) {
+ options++;
+ port->uartclk = simple_strtoul(options, NULL, 0) * 16;
+ }
printk(KERN_INFO "Early serial console at %s 0x%llx (options '%s')\n",
mmio ? "MMIO" : "I/O port",
--
