[U-Boot] [PATCHv1] mx53ppd: Change UART clock divider for high baudrate

[Fabio Estevam]

Hi Rick and Sebastian,

On Thu, Feb 15, 2018 at 2:15 PM, Sebastian Reichel
<sebastian.reichel at collabora.co.uk> wrote:
> From: Rick Bronson <rick at efn.org>
>
> Allow higher UART baud rates for communications to ACHC at 13.5 MBaud

What does ACHC mean?

> Done in u-boot since it changes a divider common to all UARTs, including
> the console. If it were done in Linux we would get garbled characters
> during the handoff from u-boot to the kernel.

It would be nice to explain a bit how you achieve the higher baud rates.

Looks like you don't use PLL2 as the UART clock anyomore.

Please expland a bit further on the new UART clock sheme.

>
> Signed-off-by: Sebastian Reichel <sebastian.reichel at collabora.co.uk>
> ---
>  arch/arm/mach-imx/mx5/lowlevel_init.S | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm/mach-imx/mx5/lowlevel_init.S b/arch/arm/mach-imx/mx5/lowlevel_init.S
> index f5bc6728b7c2..ee4c3afd2fed 100644
> --- a/arch/arm/mach-imx/mx5/lowlevel_init.S
> +++ b/arch/arm/mach-imx/mx5/lowlevel_init.S
> @@ -319,11 +319,13 @@ setup_pll_func:
>         ldr r1, =0x00016154
>         str r1, [r0, #CLKCTL_CBCMR]
>
> +#if !defined(CONFIG_TARGET_MX53PPD)

It would be better if this option could be a generic one, something
like CONFIG_MX53_SERIAL_HIGHBAUD, so that other boads could use it if
needed.