status = "okay" vs. "disabled" in soc.dtsi or board.dts

[Stephen Warren]

Grant, Rob, et al.,

As background, consider an SoC with 4 SD/MMC controllers, and that most
boards will only use 1 or 2 of these controllers. Attempting to initialize
the other would be pointless since nothing is connected, cause meaningless
kernel error spew, etc.

This could be handled in two ways:

1)

For all such devices, place status="disabled" in $soc.dtsi, and override
this in $board.dts for the devices that are actually used on the board.

2)

Do nothing in particular in $soc.dtsi, thus leaving everything enabled,
and disable anything unused in $board.dts.


We've had this discussion before, and if I understood you (Grant)
correctly, you stated during review of some Tegra .dts files that (2)
was the de-facto practice, and hence that's what the current Tegra
.dts files in the kernel do.

However, I've just noticed that we aren't consistent about this across
SoCs; IMX and Atmel appear to do (1) whereas Tegra and Exynos do (2).
(1) seems a little more direct; the $board.dts files only contain
configuration for devices they use, rather than also having to disable
devices they don't. Can Tegra (and Exynos) switch?

Thanks.

-- 
nvpublic