FIX (peripheral): add support for instantiating multiple peripherals of same type

[T-K-233]

changelog:changed

Change how peripherals are included, so that user can instantiate multiple peripheral devices of same type in chip config.

Related PRs / Issues:

Type of change:

• Bug fix
• New feature
• Other enhancement

Impact:

• RTL change
• Software change (RISC-V software)
• Build system change
• Other

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[abejgonzalez]

I think an API that makes more sense to me is: class WithUARTOverride(no: Int, ...) where the no is the index in the PeripheryUARTKey Seq to override.

[abejgonzalez]

Or if you want to truely override the entire key I would have two APIs:

• one called WithUARTOverride that takes a Seq of tuples (enforced to be size of 2 - where the 1st element in the tuple is the address and the 2nd is the baudrate) that gets unrolled into multiple UARTParams.
• another that is the additive uart (same as the current WithUART)

[jerryz123]

I actually prefer the style here, as it matches how the WithNCores behaves

[T-K-233]

Ideally, we should get rid of the default UART (i.e. when user does not specify WithUART, we shouldn't include a UART in the SoC).

I could not find where it adds the default UART though, so this is a hack to override the default parameter, and also to prevent error message when using WithUART only.

[abejgonzalez]

The default UART is given here:

chipyard/generators/chipyard/src/main/scala/config/AbstractConfig.scala

Line 48 in 44abc91

new chipyard.config.WithUART ++ // add a UART

We have the CY config have a UART by default so that we can boot Linux easily in SW-RTL sims.

I actually think we can change the default implementation of WithUART here:

chipyard/generators/chipyard/src/main/scala/config/fragments/PeripheralFragments.scala

Lines 35 to 38 in 44abc91

	class WithUART(baudrate: BigInt = 115200) extends Config((site, here, up) => {
	case PeripheryUARTKey => Seq(
	UARTParams(address = 0x54000000L, nTxEntries = 256, nRxEntries = 256, initBaudRate = baudrate))
	})

To essentially be the "override" config (i.e. generalize it to override all the Seq[UARTParams] given a Seq of tuples) and renaming it as such WithUARTOverride. Then we can keep the current implementation of WithUART seen here (where it's additive and like WithN...Cores) and just move it to the PeripheralFragments.scala file.

[jerryz123]

We want to keep the default UART. There's hardly a good reason to build a SoC without a UART....

The default UART config should be close to "universal".. that is, rarely should users need to change the address/params of that UART.

Additional WithUART flags can add more UARTs at other addresses to the system..

We should have an additional WithUARTOverride fragment for special cases when the default UART settings are not correct ... I don't think that fragment will be used very frequently, but it should be available at least.