uart ns16550 driver add DesignWare APB Busy Detect interrupt support

[IRISZZW]

Is your enhancement proposal related to a problem? Please describe.

The DesignWare APB UART has a feature which causes a new Busy Detect interrupt to be generated
if it's busy when the LCR is written.

When Busy Detect interrupt generated, we need to read the UART status register to reset it.

Similar fix in Linux kernel: torvalds/linux@beab697

relative issue; #36254

[IRISZZW]

@dcpleung @nashif @jenmwms @aasthagr this interrupt not exist in standard ns16550 uart, is there any suggestion how to add the support for it?

[dcpleung]

TBH, I wonder if we should separate the current 16550 driver into two: one for basic 16550, and one for DesignWare:

• Fewer #ifdef in 16550 driver for DW features.
• No need for all those macros for I/O port access in DW driver.
• Easier to extend DW driver, without the need to re-verify basic 16550 functionality.

[abrodkin]

AFAIK an issue in question was only seen on ARC HSDK (v1 or original) board when Zephyr application that uses UART IRQs was started after auto-started (by boot-ROM) U-Boot. In other words if U-Boot auto-start is disabled by a DIP-switch (or equally U-Boot image was never programmed in the on-board SPI flash) this problem won't be reproduced.

[zephyrbot]

Hi @evgeniy-paltsev,

This issue, marked as an Enhancement, was opened a while ago and did not get any traction. Please confirm the issue is correctly assigned and re-assign it otherwise.

Please take a moment to review if the issue is still relevant to the project. If it is, please provide feedback and direction on how to move forward. If it is not, has already been addressed, is a duplicate, or is no longer relevant, please close it with a short comment explaining the reason.

@IRISZZW you are also encouraged to help moving this issue forward by providing additional information and confirming this request/issue is still relevant to you.

Thanks!