[PATCH v2 3/7] tty/serial: convert 8250 to generic earlycon

Rob Herring robherring2 at gmail.com
Tue Jun 10 15:38:22 PDT 2014

On Tue, Jun 10, 2014 at 3:52 PM, Tony Luck <tony.luck at gmail.com> wrote:
> On Mon, Jun 9, 2014 at 4:18 PM, Rob Herring <robherring2 at gmail.com> wrote:
>> It should do auto detect of the baud-rate if it is not specified which
>> for 8250 is just reading the baud-rate divider and calculating the
>> baud-rate using the uart clock. It should just reprogram the divider
>> with the same divider value. I don't see anything obvious why this
>> would have broken.
> Something very weird is happening.  Output is good so long as I put the
> trailing ",115200" on the command line.
> But I made early_serial8250_setup() printk() the return value it got
> from probe_baud() - in case is was somehow getting 115201 or some
> other silly value ... nope. Exactly 115200.
> I also can't explain why the "noise" comes and goes a dozen
> times during boot,
> Does some other place in the kernel look at the "uart..." command
> line argument?

Would you be using drivers/firmware/pcdp.c as that is ia64 only? That
shouldn't have an impact that I can see.

Can you print the options string in serial8250_console_setup? Maybe it
is getting lost when the real console is setup.


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