This splits out the decoding done in the decode0 step into a separate
predecoder, used when writing instructions into the icache. The
icache now holds 36 bits per instruction rather than 32. For valid
instructions, those 36 bits comprise the bottom 26 bits of the
instruction word, a 9-bit insn_code value (which uniquely identifies
the instruction), and a zero in the MSB. For illegal instructions,
the MSB is one and the full instruction word is in the bottom 32 bits.
Having the full instruction word available for illegal instructions
means that it can be printed in the log when simulating, or in future
could be placed in the HEIR register.
If we don't have an FPU, then the floating-point instructions are
regarded as illegal. In that case, the insn_code values would fit
into 8 bits, which could be used in future to reduce the size of
decode_rom from 512 to 256 entries.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This uses the JTAGG primitive which is similar to BSCANE2.
The LUT4 delay approach came from Florian and Greg in
https://github.com/enjoy-digital/litex/pull/1087
Has been tested on an OrangeCrab with 48MHz sysclk
FT232H up to 30MHz (though libusb/urjtag is by far the bottleneck vs
the JTAG clock)
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
This moves the calculation of the result for popcnt* into the
countbits unit, renamed from countzero, so that we can take two cycles
to get the result. The motivation for this is that the popcnt*
calculation was showing up as a critical path.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
top-orangecrab0.2 is a copy of top-arty with various changes.
USRMCLK is added for the SPI clock
ethernet is removed
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Yosys changed command line behaviour following the v0.12 release. Work
around this by using read_verilog, which maintains the old behaviour.
This should work fine for current yosys and be compatible with
future releases.
See https://github.com/YosysHQ/yosys/issues/3109
Signed-off-by: Joel Stanley <joel@jms.id.au>
The existing orange crab target is for an older board with a
LFE5UM5G-85F device. Newer orange crab boards (v0.21) have a
LFE5U-85F device in the -8 speed grade, so make a new target for them
called ORANGE-CRAB-0.21.
Also add flags to ecppack to indicate that the bitstream should be
compressed and can be loaded at 38.8MHz.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
I'm not sure why I set the input frequency for the Orange Crab to 50MHz.
Since we easily make timing now, bump our output frequency to 48MHz as
well.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
While verilator finds the correct top level module with the current
setup, if we start adding simulation models it can get confused.
Explicitly specify the top level module.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Recent versions of verilator support the --build option, allowing
us to remove a step.
Also add a Docker image for verilator.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
This is the start of an implementation of a PMU according to PowerISA
v3.0B. Things not implemented yet include most architected events,
the BHRB, event-based branches, thresholding, MMCR0[TBCC] field, etc.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
We've been investigating why the barrel rotator uses an enormous
number of cells on the yosys ECP5 target. Eventually it was narrowed
down to the -abc9 -nowidelut options, which see the cell count go from
4985 cells to 841 cells.
Using the same options on an Orange Crab build reduces the cell count
from 50864 to 36085. The main differences:
LUT4 31040 -> 25270
PFUMX 6956 -> 0
L6MUX21 1746 -> 0
CCU2C 2066 -> 1759
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
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 also removes the dependencies these testbenches have on VHPIDIRECT.
The use of VHPIDIRECT limits the number of available simulators for the project. Rather than using
foreign functions the testbenches can be implemented entirely in VHDL where equivalent functionality exists.
For these testbenches the VHPIDIRECT-based randomization functions were replaced with VHDL-based functions.
The testbenches recognized by VUnit can be executed in parallel threads for better simulation performance using
the -p option to the run.py script
Signed-off-by: Lars Asplund <lars.anders.asplund@gmail.com>
This adds a GPIO controller which provides 32 bits of I/O. The
registers are modelled on the set used by the gpio-ftgpio010.c driver
in the Linux kernel. Currently there is no interrupt capability
implemented, though an interrupt line from the GPIO subsystem to the
XICS has been connected.
For the Arty A7 board, GPIO lines 0 to 13 are connected to the pins
labelled IO0 to IO13 on the "shield" connector, GPIO lines 14 to 29
connect to IO26 to IO41, GPIO line 30 connects to the pin labelled A
(aka IO42), and GPIO line 31 is connected to LED 7.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This changes the way GPR hazards are detected and tracked. Instead of
having a model of the pipeline in gpr_hazard.vhdl, which has to mirror
the behaviour of the real pipeline exactly, we now assign a 2-bit tag
to each instruction and record which GSPR the instruction writes.
Subsequent instructions that need to use the GSPR get the tag number
and stall until the value with that tag is being written back to the
register file.
For now, the forwarding paths are disabled. That gives about a 8%
reduction in coremark performance.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Our Makefiles need some work, but for now create an FPGA target:
make FPGA_TARGET=verilator microwatt-verilator
ghdl and yosys can use containers using PODMAN=1 or DOCKER=1
options.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
yosys and verilator did not like us passing in the verilog and
exporting it again. Pass the source directly to verilator instead.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
This adds the skeleton of a floating-point unit and implements the
mffs and mtfsf instructions.
Execute1 sends FP instructions to the FPU and receives busy,
exception, FP interrupt and illegal interrupt signals from it.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
This adds a true random number generator for the Xilinx FPGAs which
uses a set of chaotic ring oscillators to generate random bits and
then passes them through a Linear Hybrid Cellular Automaton (LHCA) to
remove bias, as described in "High Speed True Random Number Generators
in Xilinx FPGAs" by Catalin Baetoniu of Xilinx Inc., in:
https://pdfs.semanticscholar.org/83ac/9e9c1bb3dad5180654984604c8d5d8137412.pdf
This requires adding a .xdc file to tell vivado that the combinatorial
loops that form the ring oscillators are intentional. The same
code should work on other FPGAs as well if their tools can be told to
accept the combinatorial loops.
For simulation, the random.vhdl module gets compiled in, which uses
the pseudorand() function to generate random numbers.
Synthesis using yosys uses nonrandom.vhdl, which always signals an
error, causing darn to return 0xffff_ffff_ffff_ffff.
This adds an implementation of the darn instruction. Darn can return
either raw or conditioned random numbers. On Xilinx FPGAs, reading a
raw random number gives the output of the ring oscillators, and
reading a conditioned random number gives the output of the LHCA.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Means we can synthesize at 40Mhz (where we currently make timing) and
our UART still works at 115200 baud.
Tested working hello world unmodified with ECP5 eval board. Orange
Crab is updated but is untested.
Signed-off-by: Michael Neuling <mikey@neuling.org>
This allows these targets
FPGA_TARGET=ORANGE-CRAB make microwatt.bit
FPGA_TARGET=ECP5-EVN make microwatt.bit
Default is ORANGE-CRAB as before
ECP5-EVN is tested on real hardware. The console only works at 38400 so
needs this in console.c and a recompile of hello_world to work:
-#define UART_FREQ 115200
+#define UART_FREQ 38400
With this 'FPGA_TARGET=ECP5-EVN make prog' works on the ECP5 dev board.
Signed-off-by: Michael Neuling <mikey@neuling.org>
This is useful to specify "-noflatten" which helps CI stay under 8GB
limit.
Normally the AUTONAME stage of yosys will take around 10GB if
operating on the whole design. With -noflatten, AUTONAME occurs only
per VHDL entity, so only consumes around 3GB of memory. This gets us
under the limitations on github actions.
More discussion here:
https://github.com/antonblanchard/microwatt/pull/209#issuecomment-652186078
Signed-off-by: Michael Neuling <mikey@neuling.org>
nextpnr will leave an output file around even when it errors out, so
build to a tmp file and move it when we succeed so we don't confuse
make.
Signed-off-by: Michael Neuling <mikey@neuling.org>
The fetch2 stage existed primarily to provide a stash buffer for the
output of icache when a stall occurred. However, we can get the same
effect -- of having the input to decode1 stay unchanged on a stall
cycle -- by using the read enable of the BRAMs in icache, and by
adding logic to keep the outputs unchanged on a clock cycle when
stall_in = 1. This reduces branch and interrupt latency by one
cycle.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Paul Mackerras
Matt Johnston
Michael Neuling