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

[Heinrich Schuchardt]

On 9/22/22 15:14, Pali Rohár wrote:
> On Thursday 22 September 2022 13:27:51 Simon Glass wrote:
>> Hi,
>>
>> On Wed, 21 Sept 2022 at 15:56, Tom Rini <trini at konsulko.com> wrote:
>>>
>>> On Wed, Sep 21, 2022 at 03:54:13PM +0200, Pali Rohár wrote:
>>>> On Wednesday 21 September 2022 09:49:24 Tom Rini wrote:
>>>>> 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
>>>>
>>>> It looks like that some efi stuff overloads u-boot functions, in this
>>>> case newly added flush() function.
>>>>
>>>> Any idea how to handle this issue?
>>
>> I think you should rename the EFI flush() function to something like
>> efi_flush().
>
> Ok! I renamed EFI flush() function to efi_flush().
>
> I put all patches into github pull request which started CI test:
> https://github.com/u-boot/u-boot/pull/241

When merging, please, use
[PATCH 1/1] efi_selftest: prefix test functions with efi_st_
https://lists.denx.de/pipermail/u-boot/2022-September/495334.html

Best regards

Heinrich

>
>>>>
>>>> The only option which I see how to address it is to revert those changes
>>>> in source files which always calls flush() function and replace them by
>>>> my first attempt which use guard #ifdef to ensure that flush() call is
>>>> completely eliminated at preprocessor stage when efi is enabled.
>>>
>>> Adding in Heinrich.
>>>
>>> --
>>> Tom
>>
>> Regards,
>> Simon