Buffered STDIN/STDOUT crashes on RTL8195AM and Ublox ODIN W2

[SeppoTakalo]

Description

When sending bytes bidirectionally to Uart that handles STDIN/STDOUT the Realtek 8195 seems to crash.
This is basically same issue that was reported in #6358 but requires faster speed than what humans can type.

To reproduce:

mbed new serial-test
cd serial-test
cd mbed-os
git checkout master
cd ..

Then create main.cpp and mbed_app.json as follows:

main.cpp

#include "mbed.h"

int main() {
    printf("Started!\r\n");

    while (true) {
        int c = getchar();
        if (c != EOF) {
            printf("Input: %c\r\n", c);
        } else {
            return 0;
        }
    }
}

mbed_app.json

{
    "target_overrides": {
        "*": {
            "platform.stdio-buffered-serial": true
        }
    }
}

Now compile and run the program.

It first seems to work, if you type in anything. But if you copy&paste some string that is longer that 10 characters, then it crashes.

So for example, paste following to the serial terminal: 0123456789A
Output would be:

Started!
Input: 0
Input: 1
Input: 2
Input: 3
Input: 4
Input: 5
Input: 6
Input: 7

And then it does not respond anymore

Note: If you set stdio-buffered-serial to false it does not crash.

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[SeppoTakalo]

Just verified that Ublox EVK ODIN W2 also crashes somehow if baud rate is set to 115200 and paste a bit longer text:
0123456789A0123456789A0123456789A0123456789A0123456789A0123456789A0123456789A0123456789A0123456789A

So for Ublox EVK ODIN W2 use following mbed_app.json

{
    "target_overrides": {
        "*": {
            "platform.stdio-buffered-serial": true,
            "platform.stdio-baud-rate": 115200
        }
    }
}

[Mirrored to Jira]

[SeppoTakalo]

Verified that does not crash on K66F
[Mirrored to Jira]

[samchuarm]

adding @ARMmbed/team-realtek @M-ichae-l , Hi Michael, please help look into this STDIN/STDOUT crash and address it for RTL8195AM. Thanks.
[Mirrored to Jira]

[samchuarm]

Adding @AdamZhang0124
[Mirrored to Jira]

[adbridge]

Internal Jira reference: https://jira.arm.com/browse/IOTPART-6510

[jenia81]

This issue also affects SDA (secure device access) project that runs on Sales Demo Device (WEM device, modification of Ublox Odin W2). When running SDA example application with Serial it crashes from time to time. @TaniaMirzin, can provide more details if needed

[samchuarm]

@M-ichae-l , can you please verify this STDIN/STDOUT crash for RTL8195AM?

[M-ichae-l]

@SeppoTakalo
I have followed your process. However, I am not able to produce the error with all three compilers (GCC, ARM, and IAR). My side the UART is working perfectly. Could you please check again? Thank you.