hw: Add possibility of removing CDC cut between SoC and Cluster

[Lore0599]

Cluster Adapter CDC

This PR introduces the possibility of enabling or disabling the CDC between the SoC and the cluster domains.
Additionally, when the CDC is enabled, it adjusts the parameter for the input FIFO depth to avoid bandwidth limitations between the two domains.

[Xeratec]

As far as I can tell, the EnAxiCdc options has no effect on what clock source is used on the cluster. In this case, it is possible that there is no CDC and the cluster is running at a different frequency than the host. Would this be a problem?

[Lore0599]

@Xeratec Yes, the parameter is used only to select whether you want the CDC or not. However, the clock signal in the RTL is still different, which means that when building the SoC top level, you must ensure that the cluster clock runs at the same frequency as the SoC clock. If this is not ensured, the system will not work.

[fischeti]

LGTM!

[fischeti]

@Xeratec Yes, the parameter is used only to select whether you want the CDC or not. However, the clock signal in the RTL is still different, which means that when building the SoC top level, you must ensure that the cluster clock runs at the same frequency as the SoC clock. If this is not ensured, the system will not work.

You could also use the EnAxiCdc parameter in the testbench to assign the cluster clock to the soc clock

[Xeratec]

I agree with the comment from @fischeti. Additionally, there seems to be an accidental change and I have a question about the newly added TODO comment.

[Lore0599]

I agree with the comment from @fischeti. Additionally, there seems to be an accidental change and I have a question about the newly added TODO comment.

[Lore0599]

@Xeratec Yes, the parameter is used only to select whether you want the CDC or not. However, the clock signal in the RTL is still different, which means that when building the SoC top level, you must ensure that the cluster clock runs at the same frequency as the SoC clock. If this is not ensured, the system will not work.

You could also use the EnAxiCdc parameter in the testbench to assign the cluster clock to the soc clock

Since I want to ensure that the user configures the cluster adapter correctly, I introduced the AXI CDC enable flag into ChimeraClusterCfg. This structure will be set by the user when integrating a new cluster.
The same structure is also used in the testbench to check that, when the CDC is disabled, the two clock frequencies are identical; otherwise, a fatal error is triggered.

@fischeti @Xeratec what do you think? If this looks good, we can merge the PR.

[Xeratec]

Looks good, I just have one comment about the GCC version. Feel free to proceed as you think is best and merge afterwards.

[Xeratec]

You got lazy? 😅

[Xeratec]

Are you sure about this change? I would avoid using the default version but explicitly specify the version. Before we used riscv64-gcc-12.2.0, now it is pulp-gcc-2.5.0 (default).