Re: [PATCH v2 2/2] hw/ppc: e500: Fill in correct <clock-frequency> for the serial nodes

[Bin Meng]

On Thu, Feb 4, 2021 at 12:58 PM David Gibson
<david@gibson.dropbear.id.au> wrote:
>
> On Wed, Feb 03, 2021 at 10:24:48PM +0800, Bin Meng wrote:
> > From: Bin Meng <bin.meng@windriver.com>
> >
> > At present the <clock-frequency> property of the serial node is
> > populated with value zero. U-Boot's ns16550 driver is not happy
> > about this, so let's fill in a meaningful value.
>
> Are you sure this is correct - that is that the serial clock is really
> the same as the overall system clock?  Quite often there's some kind
> of divider in between.
>

Yes, see the U-Boot codes include/configs/qemu-ppce500.h

#define CONFIG_SYS_NS16550_CLK          (get_bus_freq(0))

get_bus_freq(0) eventually returns the platform clock frequency which is 400MHz.

But the value doesn't matter anyway for QEMU. We don't emulate any
baud rate specific thing for a serial port. We only need a sane value
that is non-zero.

Regards,
Bin