[PATCH v2] bsps: Add BSP_FLUSH_KERNEL_CHAR_OUTPUT BSP option

[Sebastian Huber]

On 21.03.24 00:28, Chris Johns wrote:
> On 21/3/2024 2:11 am, Sebastian Huber wrote:
>> On 19.03.24 18:44, Chris Johns wrote:
>>> On 20/3/2024 2:03 am, Sebastian Huber wrote:
>>>> On 19.03.24 14:50, Kinsey Moore wrote:
>>>>> The xilinx-zynqmp-rpu bsp_reset() is modified, but not included in the spec
>>>>> file for the new option. Its family differs from the arm/xilinx-zynqmp BSP
>>>>> family with a -rpu suffix.
>>>> Yes, but this BSP is quite new. I would prefer to let it not flush anything by
>>>> default to carry out a reset.
>>>>
>>>>> I'd be fine with this being enabled for the AArch64 BSPs as well, but I
>>>>> imagine that's better as a separate patch.
>>>> Why should it be enabled by default? The arm/xilinx-zynq and arm/xilinx-zynqmp
>>>> BSPs were the only ones doing an UART flush in the general termination
>>>> procedure. It probably was done to address a specific use case (maybe test
>>>> runs).
>>> Is the issue the flush is before an infinite loop which means the UART FIFO
>>> should drain?
> 
> What is the issue you are wanting to solve removing the flush?

The bsp_reset() function should reset the system and do nothing more. 
Doing additional things like flushing an UART device may not make sense 
for all applications. Some applications may not use the UART device, so 
it may not be initialized and powered off.  Some applications may use it 
with an application-specific protocol which doesn't like the additional 
four '\r' during reset. Doing a UART flush takes some time and some 
applications may prefer a fast reset time. The bsp_reset() is the wrong 
place to do add specific cleanup functions. Applications can customize 
the termination procedure with their own fatal error extension, 
destructors, and exit handlers.

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