[U-Boot] [PATCH v2] serial: pl01x: Add support for devices with the rate pre-configured.

[Stephen Warren]

On 03/20/2016 12:06 AM, Stephen Warren wrote:
> On 03/15/2016 08:36 PM, Stephen Warren wrote:
>> On 03/13/2016 07:16 PM, Eric Anholt wrote:
>>> For Raspberry Pi, we had the input clock rate to the pl011 fixed in
>>> the rpi.c file, but it may be changed by firmware due to user changes
>>> to config.txt.  Since the firmware always sets up the uart (default
>>> 115200 output unless the user changes it), we can just skip our own
>>> uart init to simplify the boot process and more reliably get serial
>>> output.
>>
>> Tested-by: Stephen Warren <swarren at wwwdotorg.org>
>> # on RPi B+ and RPi 2
>
> Sorry, I take this Tested-by back. With the latest firmware (which has
> some modifications intended to initialize either the PL01x or the mini
> UART depending on which the kernel will actually use), this patch causes
> U-Boot not to boot at all. I'm pretty sure this is a FW bug (since even
> without this patch the UART doesn't work, but U-Boot does at least boot
> and can be used over HDMI/usbkbd), but I'd still prefer not to apply
> this until the FW is working again and we can double-check everything.
>
> Hopefully this will be resolved in
> https://github.com/raspberrypi/firmware/issues/553 soon.

We can go ahead with this patch now; the FW behaviour has been accepted 
as a bug, and fixed in a new FW release.