We want to make sure we never complete more than one
instruction per cycle, or write back more than one GPR
or CR per cycle.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
We only need two write ports for load with update instructions.
Having two write ports just for this instruction is expensive.
For now we will force them to be the only instruction in the
pipeline, and take two cycles of writeback.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
It simulated fine, but didn't synthesize. Fix some obvious issues
to get us going again.
Fixes: 9fbaea6f08 ("Rework CR file and add forwarding")
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Right now we continually print all 3 possible GPRs an instruction
may be using. Add signals so we only print GPRs when they are
actually read. This should hopefully optimise away when synthesized.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Handle the CR as a single field with per nibble enables. Forward any
writes in the same cycle.
If this proves to be an issue for timing, we may want to revisit
this in the future. For now, it keeps things simple.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
This adds support for the Digilane Cmod A7-35.
I had to use the MMCM because the clock (12 MHz) is below the PLL
minimum of 19 MHz.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
I wasn't waiting to get a wishbone ack back on stores before continuing.
This creates all sorts of problems when we add pipelining and send
loads and stores down the pipe faster.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
The old reset code was overly complicated and never worked properly.
Replace it with a simpler sequence that uses a couple of shift registers
to assert resets:
- Wait a number of external clock cycles before removing reset from
the PLL.
- After the PLL locks and the external reset button isn't pressed,
wait a number of PLL clock cycles before removing reset from the SOC.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
The decode2 stage was spaghetti code and needed cleaning up.
Create a series of functions to pull fields from a ppc instruction
and also a series of helpers to extract values for the execution
units.
As suggested by Paul, we should pass all signals to the execution
units and only set the valid signal conditionally, which should
use less resources.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Some VHDL compilers like verific [1] don't like these, so let's remove
them. Lots of random code changes, but passes make check.
Also add basic script to run verific and generate verilog.
1. https://www.verific.com/
Signed-off-by: Michael Neuling <mikey@neuling.org>
- Switch to using ghdl/vunit:llvm, it's a smaller container
- We need to "apt update" before installing packages
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Mikey points out that our stack grows down from 512kB and our
heap is below that too, so we can reduce our BRAM requirements,
which allowing some smaller FPGA boards to work. Not sure why
I thought we were using memory between 512kB and 1MB.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Anton Blanchard
Michael Neuling