No support for UARTs with shared interrupt on some STM32 targets

[amcnicoll]

Description of defect

On some targets (at least STM32L0, STM32G0) with interrupts shared between multiple UART peripherals, it is not possible to use the shared UARTs at the same time. When the second of the shared UARTs calls serial_irq_set(), the vector to the first UART's IRQ handler is broken.

I believe this problem was handled for STM32F0 by combining the handler for each peripheral into one (uart3_8_irq) and attaching it regardless of whether serial_irq_set() is running for UART3 or UART8. Seems like the same thing should have been done for STM32L0 and STM32G0.

If there was a documented user-land workaround for this issue, I wasn't able to find it. Thanks!

Target(s) affected by this defect ?

STM32L0, STM32G0

Toolchain(s) (name and version) displaying this defect ?

n/a but recent GCC_ARM

What version of Mbed-os are you using (tag or sha) ?

Issue present in master as of this writing (1443257)

What version(s) of tools are you using. List all that apply (E.g. mbed-cli)

Discovered while working on a PlatformIO project with the mbed framework (Core 5.2.4)

How is this defect reproduced ?

Make a project with 2 BufferedSerial objects corresponding to 2 shared UARTs.
For example, this issue was discovered while trying to use USART4 and USART5 on STM32L071.
Suppose you instantiate USART4 first and USART5 second.
The USART5 handler takes over the USART4_5_IRQn.
If data is sent to USART4, the application hangs since the RXNE flag is never cleared by the USART5 handler.

[0xc0170]

cc @ARMmbed/team-st-mcd

[jeromecoutant]

Hi

I confirm there is an issue with:

• STM32L0 and USART4_5_IRQHandler
• STM32G0 and USART3_4_LPUART1_IRQHandler/USART3_4_5_6_LPUART1_IRQHandler

Any help is welcomed

[amcnicoll]

@jeromecoutant, here is how I patched my serial_device.c for STM32L0, in case it's helpful until the devs fix this (change extension to *.c)
serial_device_patch.txt

[jeromecoutant]

Thx @amcnicoll
Do you think you could try to propose a pull request (after pushing your commit in your repo) ?
https://os.mbed.com/docs/mbed-os/v6.15/contributing/index.html

[amcnicoll]

I've got the commit on a local branch. Am I right in understanding that I must first be granted access to the ARMmbed organization in order to push my branch and create the PR?

[0xc0170]

I've got the commit on a local branch. Am I right in understanding that I must first be granted access to the ARMmbed organization in order to push my branch and create the PR?

Create a fork of Mbed Os and create a branch where you can add your commits. You can create a new pull request from your forked repository to this one.

[amcnicoll]

Thanks, it's up #15221

[0xc0170]

Fixed via #15221