- do the CSR alignment update only if CPU is not CPUNone.
- revert PointToPoint interconnect when 1 master and 1 slave since this will
break others use cases and will prevent mapping slave to a specific location.
It's probably better to let the synthesis tools optimize the 1:1 mapping directly.
- add with_soc_interconnect parameter to add_sdram that defaults to True. When
set to False, only the LiteDRAMCore will be instantiated and interconnect with
the SoC will not be added.
This should also improve Wishbone timings.
Tested on iCEBreaker:
./icebreaker.py --cpu-type=None --uart-name=uartbone --csr-csv=csr.csv --build --flash
With the following script:
#!/usr/bin/env python3
import sys
from litex import RemoteClient
wb = RemoteClient()
wb.open()
# # #
print("scratch: 0x{:08x}".format(wb.regs.ctrl_scratch.read()))
errors = 0
for i in range(2):
for j in range(32):
wb.write(wb.mems.sram.base + 4*j, i + j)
for j in range(32):
if wb.read(wb.mems.sram.base + 4*j) != (i + j):
errors += 1
print("sram errors: {:d}".format(errors))
# # #
wb.close()
Currently, we create a wishbone interface with the default address
width (30 bits) for the bridge. Instead, create an interface that
has the same number of address bits as the CSR bus.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
When creating standalone IP cores such as standalone LiteDRAM without
a CPU, the CSR are presented externally via a wishbone with just enough
address bits to access individual CSRs (14), and no address decoding
otherwise. It is expected that the design using such core will have
its own address decoder gating cyc/stb.
However, such a design might still need to use LiteX code such as
the sdram init code, which relies on the generated csr.h. Thus we
want to be able to control the CSR base address used by that generated
csr.h.
This could be handled instead by having the "host" code provide
modified csr_{read,write}_simple() that include the necessary base
address. However, such an approach would make things complicated
if the design includes multiple such standalone cores with separate
CSR busses (such as LiteDRAM and LiteEth).
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
When creating a standalone LiteDRAM core with no CPU, there is
no need to create a wishbone slave to LiteDRAM interface.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This creates a lot of useless churn in the resulting verilog. Instead
use a point to point interconnect in that case.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
