[PATCH v3 0/6] console: Implement flush() function

Tom Rini trini at konsulko.com
Wed Sep 21 15:49:24 CEST 2022


On Mon, Sep 05, 2022 at 11:31:15AM +0200, Pali Rohár wrote:

> On certain places it is required to flush output print buffers to ensure
> that text strings were sent to console or serial devices. For example when
> printing message that U-Boot is going to boot kernel or when U-Boot is
> going to change baudrate of terminal device.
> 
> Some console devices, like UART, have putc/puts functions which just put
> characters into HW transmit queue and do not wait until all data are
> transmitted. Doing some sensitive operations (like changing baudrate or
> starting kernel which resets UART HW) cause that U-Boot messages are lost.
> 
> Therefore introduce a new flush() function, implement it for all serial
> devices via pending(false) callback and use this new flush() function on
> sensitive places after which output device may go into reset state.
> 
> This change fixes printing of U-Boot messages:
> "## Starting application at ..."
> "## Switch baudrate to ..."
> 
> Changes in v3:
> * add macro STDIO_DEV_ASSIGN_FLUSH()
> * fix commit messages
> * remove changes from serial.c
> 
> Changes in v2:
> * split one big patch into smaller 6 patches
> * add config option to allow disabling this new function
> 
> Pali Rohár (6):
>   sandbox: Add function os_flush()
>   console: Implement flush() function
>   serial: Implement flush callback
>   serial: Implement serial_flush() function for console flush() fallback
>   serial: Call flush() before changing baudrate
>   boot: Call flush() before booting

Including the change you suggested to 4/6 to fix that build issue,
there's at least one more large issue that prevents CI from getting too
far:
https://source.denx.de/u-boot/u-boot/-/pipelines/13534
and they all have a failure similar to:
https://source.denx.de/u-boot/u-boot/-/jobs/500794#L51

Please see
https://u-boot.readthedocs.io/en/latest/develop/ci_testing.html for how
to run CI on the world yourself before submitting v4. Thanks!

-- 
Tom
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