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Reduce the size of icache to help yosys ECP5 builds (#303)

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The icache RAM is currently LUT ram not block ram. This massively
bloats the icache size. We think this is due to yosys not inferencing
the RAM correctly but that's yet to be confirmed.

Work around this for now by reducing the default size of the icache
RAM for the ECP5 builds.

On the ECP5 85K builts, this gets us from 95% down to 76% and helps
our CI to pass.

Signed-off-by: Michael Neuling <mikey@neuling.org>
This commit is contained in:
Michael Neuling
2021-07-31 11:18:39 +10:00
committed by GitHub
parent f9654428ff
commit d7458d5beb
2 changed files with 7 additions and 1 deletions
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6
Makefile
View File

@@ -143,6 +143,10 @@ RAM_INIT_FILE=hello_world/hello_world.hex
FPGA_TARGET ?= ORANGE-CRAB
# FIXME: icache RAMs aren't being inferrenced as block RAMs on ECP5
# with yosys, so make it smaller for now as a workaround.
ICACHE_NUM_LINES=4
# OrangeCrab with ECP85
ifeq ($(FPGA_TARGET), ORANGE-CRAB)
RESET_LOW=true
@@ -168,7 +172,7 @@ OPENOCD_DEVICE_CONFIG=openocd/LFE5UM5G-85F.cfg
endif
GHDL_IMAGE_GENERICS=-gMEMORY_SIZE=$(MEMORY_SIZE) -gRAM_INIT_FILE=$(RAM_INIT_FILE) \
-gRESET_LOW=$(RESET_LOW) -gCLK_INPUT=$(CLK_INPUT) -gCLK_FREQUENCY=$(CLK_FREQUENCY)
-gRESET_LOW=$(RESET_LOW) -gCLK_INPUT=$(CLK_INPUT) -gCLK_FREQUENCY=$(CLK_FREQUENCY) -gICACHE_NUM_LINES=$(ICACHE_NUM_LINES)
clkgen=fpga/clk_gen_ecp5.vhd
toplevel=fpga/top-generic.vhdl

2
fpga/top-generic.vhdl
View File

@@ -13,6 +13,7 @@ entity toplevel is
CLK_FREQUENCY : positive := 100000000;
HAS_FPU : boolean := true;
HAS_BTC : boolean := false;
ICACHE_NUM_LINES : natural := 64;
LOG_LENGTH : natural := 512;
DISABLE_FLATTEN_CORE : boolean := false;
UART_IS_16550 : boolean := true
@@ -73,6 +74,7 @@ begin
CLK_FREQ => CLK_FREQUENCY,
HAS_FPU => HAS_FPU,
HAS_BTC => HAS_BTC,
ICACHE_NUM_LINES => ICACHE_NUM_LINES,
LOG_LENGTH => LOG_LENGTH,
DISABLE_FLATTEN_CORE => DISABLE_FLATTEN_CORE,
UART0_IS_16550 => UART_IS_16550