soc: sam0: Enable generic peripheral selection

[benpicco]

Make sure that when e.g. CONFIG_SERIAL is set, CONFIG_UART_SAM0 is
selected automatically when the sam0 SoC family is used.

This fixes several examples & tests that will otherwise only compile after manually tweaking the configuration.

[codecov-io]

Codecov Report

Merging #14832 into master will not change coverage.
The diff coverage is n/a.

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  Coverage   52.51%   52.51%           
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  Files         309      309           
  Lines       45048    45048           
  Branches    10419    10419           
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  Hits        23656    23656           
  Misses      16584    16584           
  Partials     4808     4808

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[galak]

We should open an enhancement request to cleanup the boards to remove enabling any peripherals by default that aren't needed.

[ulfalizer]

Why don't we do e.g. this instead? Should work out to the same thing in practice, unless I'm missing something, and it centralizes SAM0 stuff.

diff --git a/drivers/serial/Kconfig.sam0 b/drivers/serial/Kconfig.sam0
index da3a5f4209..75aa63aa3c 100644
--- a/drivers/serial/Kconfig.sam0
+++ b/drivers/serial/Kconfig.sam0
@@ -5,6 +5,7 @@
 
 menuconfig UART_SAM0
        bool "Atmel SAM0 series SERCOM USART driver"
+       default y
        depends on SOC_FAMILY_SAM0
        select SERIAL_HAS_DRIVER
        select SERIAL_SUPPORT_INTERRUPT

(Unrelated side note: Avoid the menuconfig keyword when there's no symbols following the symbol that depend on it. Looks wonky in e.g. the menuconfig interface.)

[ulfalizer]

Another option is to enable them in the board defconfig file. Might be cleanest of all.

Drawback is having to enable the dependencies too, if they're not default y.

[benpicco]

@ulfalizer that would always enable UART_SAM0, no matter if CONFIG_SERIAL is set or not.

Maybe depends on SOC_FAMILY_SAM0 && CONFIG_SERIAL wold work. But I was just copying what stm32 was doing.

[ulfalizer]

@benpicco
It shouldn't, because drivers/serial/Kconfig.sam0 is sourced within an if SERIAL, in drivers/serial/Kconfig.

I added some clarifications to how if works in the guide btw.

[benpicco]

Ah I did no see that! In this case, I might as well enable it there.
I'm feeling tempted to just enable the peripherals for all SoCs then.

[ulfalizer]

LGTM

[ulfalizer]

@benpicco
Can see all the dependencies on the reference pages for symbols btw. Shows how the file got sourced too.

The same information is shown in the menuconfig too, in the symbol information (press ?).

(Trying to plug the menuconfig, because it's handy for checking changes, even though many people don't use it otherwise.)