[PATCH v5 2/2] serial: mxc: have putc use the TXFIFO

[Fabio Estevam]

Hi Johannes,

On Wed, Nov 2, 2022 at 2:16 AM SCHNEIDER Johannes
<johannes.schneider at leica-geosystems.com> wrote:

> sadly the previously mentioned printf with a long string (longer than 32bytes) does not trigger the issue on the debug-serial...
> (running on an imx8mm -> uart3 out of 4, and with uboot/v2202.07)
>
> but what puzzles me most is that with my current setup (different tool: old analog oscilloscope replaced by an usb logic-analyzer, and a more recent software versions also on the receiving end where the problem cropped up originally) i'm currently unable to reproduce the original issue i saw - and described in the commit message :-S
> back then the situation was as follows: with the analog scope on uart4 visually comparing waveforms clearly showed different message lengths when comparing u-boot generated traffic (without the patch = short, with the patch = "correct" length) with a reference/working signal generated from within a running linux.
> the receiving end did not respond to the messages from within uboot prior to the patch; but did so with the TXFULL applied and also always when communication was initiated from linux
>
> i still would argue to keep the change, since both the linux kernel and $other bootloaders make use of the TXFULL flag

The problem is that your change is causing a regression as reported by
Tim. It can be easily reproduced.

Please help fix it, otherwise, we will need to revert your change.

Thanks,

Fabio Estevam