[PATCH 1/2] rockchip: rk3588: add support for UART2 M1 and M2 in SPL

[Quentin Schulz]

Hi Jonas,

On 4/22/24 19:41, Jonas Karlman wrote:
> Hi Quentin,
> 
> On 2024-04-22 18:41, Quentin Schulz wrote:
>> From: Quentin Schulz <quentin.schulz at theobroma-systems.com>
>>
>> UART2 controller is the controller in the reference design for debug
>> console. The default mux is M0 in that reference design. Until now, all
>> boards seemed to be using UART2M0 but RK3588 Tiger for example will be
>> using UART2M2 instead.
>>
>> Therefore, let's add support for UART2M1 and M2 as possible muxes for
>> the UART2 controller used as debug console. UART2M1 support was not
>> tested.
>>
>> The default value is M0 to match the one used currently by all devices
>> and the reference design.
> 
> Is this really necessary?
> 
> Use of board_debug_uart_init() should typically only be needed in TPL on
> Rockchip platform, and with ROCKCHIP_TPL being used it should be enough
> to use rkbin/ddrbin_tool to change uart config and just ensure correct
> pinctrl is used for uart node, and that the uart node is included in SPL
> for correct serial console use.
> 

ddrbin_tool is a blob that Rockchip refuses to provide sources of. 
Running a blob on the target is one thing, requiring our users to run a 
blob on their build machine is another thing (though I document it in 
the rST).

However... I don't think we have another way around because I just 
remembered that if you have two muxes selected for the same UART 
controller, RX won't work. So while we would have UART output for U-Boot 
if Rockchip's TPL is one mux (e.g. m0, the default) and upstream U-Boot 
another one, we wouldn't be able to interact with it.

It'll be necessary the day we have an open-source DRAM init though (I 
had to do this for PX30 for example).

The issue is that since ddrbin_tool is a blob, it's not possible to use 
it in Yocto for automatically generating the appropriate ddr bin blob 
based on uart controller, mux and baudrate. So that will be my cross to 
bear.

> May I suggest you try adding following to defconfig and drop this patch?
> 
>    # CONFIG_DEBUG_UART_BOARD_INIT is not set
> 
> I would expect that should result in same/working behavior without
> having to add any new code.
> 

It does work, thanks for the suggestion, will send a v2.

Cheers,
Quentin