[PATCH] serial: stm32: Move hard IRQ handling to threaded interrupt context

[Valentin CARON]

Hi Marek,

I test your patch with a loop-back test between usart3 and uart7 on 
STM32MP157C-DK2. It
shows a speed transfer diminution (about -1,5%), some locks during 
transfer, RT throttling etc...
(I use lszrz tool).

But finally, I think your patch is the best solution that we have.
Other solutions always throws an RT exception on a spin_lock.

Thanks,
Valentin

On 12/8/22 14:19, Marek Vasut wrote:
> On 12/8/22 11:18, Valentin CARON wrote:
>> Hi Marek,
>
> Hi,
>
>> I've got a patch in the same spirit in downstream.
>> The test campaign reveals performance issues with this patch.
>>
>> In fact, hard IRQ have been introduced in stm32-usart driver to solve 
>> performance issues due to short FIFO size (16 bytes).
>>
>> We are currently testing another patch, similar as your RFC 
>> proposition, for RT context.
>> But results are not ready yet. We can wait them before merging this 
>> big change into driver ?
>
> Can you post your patch as an RFC so others can test as well ?