Commit Graph

388 Commits (db937403ec9aff71ba8c17f68b62ea40a575f51c)
 

Author SHA1 Message Date
Anton Blanchard 9b1394e236
Merge pull request #118 from antonblanchard/bus-pipeline
Bus pipeline
5 years ago
Benjamin Herrenschmidt 98bd8b73c0 control: Reduce pipeline depth to 1
To match our one stage execute.

This might change back if we end up adding 2 stages to match the
LSU, but in that case we'll want forwards as well.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 83a8bb0238 spr: Cleanup decoding of SPR numbers
Use a function to obtain the integer number and use constants
with the architected numbers. Replace std_match with a case
statement.

This also has the side effect of returning 0 instead of some
random previous result on mfspr of an unknown SPR.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt cff4b13a9b wb_arbiter: Early master selection
This flips the arbiter muxes on the same cycle as a new request
comes in, thus avoiding a cycle latency.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt bc2acfde2f wb_arbiter: Make arbiter size parametric
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 472d8f94a2 wb_arbiter: Avoid IDLE cycle when not changing master
Consecutive accesses from the same master shouldn't need an IDLE
cycle. Completely remove the IDLE state and switch master when
the bus is idle, but stay on the last selected one between cycles.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 336f0e0690 ram: Ack stores early
Stores only need a single cycle, so we can ack them early if there
isn't an older ack already in the pipeline

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 8e0389b973 ram: Rework main RAM interface
This replaces the simple_ram_behavioural and mw_soc_memory modules
with a common wishbone_bram_wrapper.vhdl that interfaces the
pipelined WB with a lower-level RAM module, along with an FPGA
and a sim variants of the latter.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 9a63c098a5 Move log2/ispow2 to a utils package
(Out of icache and dcache)


Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 3349bdc798 ram: Add block RAM pipelining
This adds an output buffer to help with timing and allows the BRAMs
to actually pipeline.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 797b1bb045 decode: Reformat decode_types.vhdl
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt d2762e70e5 Add option to not flatten hierarchy
Vivado by default tries to flatten the module hierarchy to improve
placement and timing. However this makes debugging timing issues
really hard as the net names in the timing report can be pretty
bogus.

This adds a generic that can be used to control attributes to stop
vivado from flattening the main core components. The resulting design
will have worst timing overall but it will be easier to understand
what the worst timing path are and address them.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 48f260761b writeback: Slightly improve timing
The CR update currently depends on the complete data formatting
mux chain. This makes it source its inputs from a bit earlier in
the chian, thus improving timing a bit

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 365f60b693 simple_ram: Turn on pipelining
With a 1 cycle delay

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt c22734d0d9 wb_debug: Add wishbone pipelining support
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 3df018cdc0 icache: Add wishbone pipelining support
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt d363daa692 dcache: Add wishbone pipelining support
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt e638c3e8ae fpga/bram: Generate stall signal
This doesn't yet pipeline the block RAM, just generate a valid stall
signal so it's compatible with a pipelined master

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 37acb35773 simple_ram: Add pipelining support
The generic PIPELINE_DEPTH can be set to 0 to keep it operating
as a non-pipelined slave, or a larger value indicating
the amount of extra cycles between requests and acks.

It will always generate a valid stall signal, so it can be used
in either mode with a pipelined master (but only in non-pipelined
mode with a non-pipelined master).

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt df1a9237f6 intercon: Generate stall signals for non-pipelined slaves
So far the UART and the "miss" case. Memory will be
pipelined

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 7a4a9b6377 wb_arbiter: Forward stall signals
They are set to '1' for non-selected devices

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt b1424e859e icache_tb: Initialize stop_mark
Too much red in gtkwave..

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 79101041d6 wishbone: Add stall signal
Pipelined wishbone needs it

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 559b3bcf2d pp_uart: reformat
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Anton Blanchard 9620a76281
Merge pull request #115 from antonblanchard/reduce-wishbone
Reduce wishbone
5 years ago
Anton Blanchard 247d7d4aa0
Merge pull request #113 from mikey/exec-sim-remove
Remove SIM generic from execute1
5 years ago
Anton Blanchard 1b6c246379
Merge pull request #114 from antonblanchard/dcache
Dcache from Ben
5 years ago
Michael Neuling bd4ac06243 Remove SIM generic from execute1
This does nothing, so remove.

Signed-off-by: Michael Neuling <mikey@neuling.org>
5 years ago
Benjamin Herrenschmidt 6dd0b514ac Reduce wishbone address size to 32-bit
For now ... it reduces the routing pressure on the FPGA

This needs manual adjustment of the address decoder in soc.vhdl, at
least until I can figure out how to deal with std_match

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

# Conflicts:
#	soc.vhdl

# Conflicts:
#	soc.vhdl
5 years ago
Benjamin Herrenschmidt 1a63c39704 Make it possible to change wishbone address size
All that needs to be changed now is the size in wishbone_types.vhdl
and the address decoder in soc.vhdl

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt cb4451498f dcache: Add testbench
A very simple one for now...

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 742b21480e insn: Simplistic implementation of icbi
We don't yet have a proper snooper for the icache, so for now make
icbi just flush the whole thing

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt a0d95e791e insn: Implement isync instruction
The instruction works by redirecting fetch to nia+4 (hopefully using
the same adder used to generate LR) and doing a backflush. Along with
being single issue, this should guarantee that the next instruction
only gets fetched after the pipe's been emptied.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 6e0ee0b0db icache & dcache: Fix store way variable
We used the variable "way" in the wrong state in the cache when
updating a line valid bit after the end of the wishbone transactions,
we need to use the latched "store_way".

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 587a5e3c45 dcache: Cleanup (mostly cosmetic)
Clearly separate the 2 stages of load hits, improve naming and
comments, clarify the writeback controls etc...

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 265fbf894b icache/dcache: Make both caches 32 lines, 2 ways
Adding lines seems to add only little extra as the BRAMs aren't
full, 2 ways is our current comprimise to limit pressure on small
FPGAs. We could go to 64 lines for a little more, but timing is
becoming a bit too right to my linking on the tags/LRU path of
the icache, so let's leave it at 32 for now.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 174378b190 dcache: Introduce an extra cycle latency to make timing
This makes the BRAMs use an output buffer, introducing an extra
cycle latency. Without this, Vivado won't make timing at 100Mhz.

We stash all the necessary response data in delayed latches, the
extra cycle is NOT a state in the state machine, thus it's fully
pipelined and doesn't involve stalling.

This introduces an extra non-pipelined cycle for loads with update
to avoid collision on the writeback output between the now delayed
load data and the register update. We could avoid it by moving
the register update in the pipeline bubble created by the extra
update state, but it's a bit trickier, so I leave that for a latter
optimization.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt b513f0fb48 dcache: Add a dcache
This replaces loadstore2 with a dcache

The dcache unit is losely based on the icache one (same basic cache
layout), but has some significant logic additions to deal with stores,
loads with update, non-cachable accesses and other differences due to
operating in the execution part of the pipeline rather than the fetch
part.

The cache is store-through, though a hit with an existing line will
update the line rather than invalidate it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt 7b3df7cb05 icache: Reduce simulation warnings
This might slightly increase the logic in synthesis but avoids
us looking at uninitialized tags when not servicing an active
request

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt a38ae503ff cache_ram: Add write-enables
They will be needed by the dcache

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt e598188aca plru: Improve sensitivity list
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Anton Blanchard b963f8a6af
Merge pull request #112 from hughhalf/patch-1
Minor tweaks to README.md
5 years ago
Hugh 96b7f17e52 Minor tweaks to README.md
Few tweaks based on a newcomers experience getting an Arty A7-100 up and running

Forgot to add DCO in initial PR, now corrected.

Signed-off-by: Hugh Blemings <hugh@blemings.org>
5 years ago
Anton Blanchard 326dec4b3b
Merge pull request #110 from antonblanchard/misc
icache_tb: Improve test and include test file
5 years ago
Benjamin Herrenschmidt f74e8a4f79 icache_tb: Improve test and include test file
The icache_test.bin file was missing. This adds it (along with a python3
script to generate it).

We also add better reporting on errors

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Anton Blanchard 900c131083
Merge pull request #109 from antonblanchard/misc
Misc updates from Ben
5 years ago
Anton Blanchard e67924f55e isel takes a CR bit, not a CR field
Fix a GHDL assert in isel.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
5 years ago
Benjamin Herrenschmidt 60b05ee1e5 common: Reformat
No code change

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt bddc9327cc execute1: Remove mux on "write_data" and "rc" outputs
Only "write_enable" needs to change, this shrinks the core a bit more

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago
Benjamin Herrenschmidt da0bd89c43 crhelpers: Constraint "crnum" integer
This seems to save quite a few LUTs

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
5 years ago