[U-Boot] [linux-sunxi] [PATCH v4 00/26] sunxi: Allwinner A64: SPL support

[Jagan Teki]

On Tue, Jan 3, 2017 at 3:38 AM, jonsmirl at gmail.com <jonsmirl at gmail.com> wrote:
> I recently ran into a probably with the UARTs on the A64. Many
> Bluetooth modules (like Ampak) use the UART. The data rate of EDR BT
> is 3Mb/s with about 2.1Mb/s though put. To handle this most systems
> set the speed of the BT UART to 3Mb/s.
>
> By default the Allwinner UART clock input is OSC24. When using OSC24
> the maximum speed the UART can be set to is 1.5Mb/s. The clock input
> (apb2) can be changed over to PERIPH0x2 (1.2ghz) via the device tree
> and 3Mb/s is then supported.
>
> But... there's a problem, UART0 (the console) is using the same master
> clock source. So when you change the clock input over to PERIPH0x2 the
> console stops working. There is no mechanism in Linux to handle this
> clock source change and adjust the dividers on active uarts. So it
> would be best if this master clock was set very early in u-boot and
> then the console is adjusted to use it.
>
> Are there any downsides to making this change in u-boot?

I don't understand, did you find this behaviour with these SPL changes
or general sunxi u-boot?

thanks!
-- 
Jagan Teki
Free Software Engineer | www.openedev.com
U-Boot, Linux | Upstream Maintainer
Hyderabad, India.