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enjoy-digital / litedram

Small footprint and configurable DRAM core
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litedram_gen: Don't block user port with no CPU #292

Closed mkj closed 2 years ago

mkj commented 2 years ago

Change e52ece0b8a7 blocks access to user ports prior to dram init. As noted in https://github.com/enjoy-digital/litedram/pull/286#issuecomment-981362385 this is a problem for cpu-less designs, since the initial memtest requires the user port.

Instead enable the user port unconditionally in that case.

enjoy-digital commented 2 years ago

Thanks @mkj, this is indeed an issue with CPU-less controllers. But even in this case, blocking the other ports could be necessary so the fix was probably not flexible enough. This is fixed a bit differently with https://github.com/enjoy-digital/litedram/commit/62abf9ce0c93d4f2a5588f89716d680138cb70db that introduces a block_until_ready parameter on ports that can use set to False for the port used by the CPU for memtest in the CPU-less case.