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

[Tom Rini]

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?
> 
> 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
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