drivers: serial: pl011: Add fifo enable configuration

[soburi]

Add a setting to the devicetree for enabling or disabling
the PL011 FIFO.

fix #74914

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[xudongzheng]

Does it make sense to have fifo-enable; defined in every board?

Perhaps it would be better to define it once in the SoC DeviceTree and use /delete-property/ fifo-enable; where it should be disabled. Or have fifo-disable; option instead.

[soburi]

Generally, under the dts folder prefer "vanilla settings".
There are other devices with fifo-enable settings, but most are set under boards.

[ithinuel]

As far as I can see fifo-enable is only set in a few overlays for stm devices.
it81xx2 sets is on some peripheral instances but as far as I understand this is to explicitly allocate which i2c instance (out of 4) gets to use the fifo channels (out of 2).

This features does not seem to have significant drawbacks so is there any reason for not enabling it by default and let boards/projects set fifo-disable if they explicitly don't want it?

[soburi]

From that perspective, I am simply following the precedent set by the STM32.
There is no problem with changing it to fifo-disable.

[soburi]

I have made the change in the direction you suggested.
In this case, the default behavior does not change, so there is no need to change the settings.

[soburi]

@xudongzheng @ithinuel I changed it to fifo-disable. What do you think?

[xudongzheng]

I think fifo-disable makes more sense especially since it wouldn't change the existing behavior on out-of-tree boards.

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[xudongzheng]

commit message says "configuraition" rather than "configuration"

[soburi]

rebased.

[soburi]

@carlocaione
Could you take a look if you have time?

[soburi]

@carlocaione @ithinuel @RichardSWheatley @AlessandroLuo

Could you take a look if you have a bit of a while?