Commit Graph

68 Commits (master)

Author SHA1 Message Date
Michael Neuling da5d3ded3c
Merge pull request #409 from CodeConstruct/dev/soc-reset
Make syscon SOC reset work
6 months ago
Matt Johnston 1f5a2e8aaa soc: Expose sw_soc_reset for syscon reset
The soc itself will be reset when a syscon soc reset is triggered.

Separately, top- board files can use the sw_soc_rst signal
if they need to reset other peripherals

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
7 months ago
Matt Johnston 4bd45af739 Move alt_reset to syscon
Instead of connecting core_alt_reset to litedram init_done, it moves to
a syscon register bit. This simplifies top- files and future soc_reset
handling. sdram main.c can unset the alt_reset bit after sdram init.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
7 months ago
Benjamin Herrenschmidt 3f788e87dc soc: Fix issues with 64-bit stores to IO bridge
The IO bridge would latch the top half of write data and selection signals
when issuing the second downstream store. Unfortunately at this point the
bridge has already "accepted" the upstream store from the core (due to
stall being 0 on the cycle when stb/cyc are 1), so the values on the
wishbone signals aren't stable and might already reflect a subsequent
wishbone command.

This causes occasional data corruption of 64-bit stores through the IO
bridge.

While at it, take out a bunch of useless conditions on the data latch
path. It doesn't matter whether we is 0 or 1, we can just always latch
the data, the destination will decide whether to use the content or not,
which should save a bit of hardware.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
7 months ago
Paul Mackerras d1e8e62fee Remove option for "short" 16x16 bit multiplier
Now that we have a 33 bit x 33 bit signed multiplier in execute1,
there is really no need for the 16 bit multiplier.  The coremark
results are just as good without it as with it.  This removes the
option for the sake of simplicity.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
10 months ago
Joel Stanley dc6a4b1406 soc: Fix -Whide warning
soc.vhdl:847:9⚠️ declaration of "uart1" hides if generate statement [-Whide]
        uart1: uart_top
        ^

Signed-off-by: Joel Stanley <joel@jms.id.au>
10 months ago
Anton Blanchard a750365ffa Remove some FPGA style signal inits
These don't work on the ASIC flow, so remove them and initialise
them explicitly where required.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
1 year ago
Anton Blanchard 948f6f43a7 Allow ALT_RESET_ADDRESS to be overridden
This allows us to boot from flash for example.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
1 year ago
Paul Mackerras 4cf2921b0b soc: Re-do peripheral address decode to improve timing
This generates a series of io_cycle_* signals which are clean latches
and which become the 'cyc' signals of the wishbone buses going to
various peripherals (syscon, uarts, XICS, GPIO, etc.).  Effectively
this is done by moving the address decoding into the slave_io_latch
process.  The slave_io_type, which drives the multiplexer which
selects which wishbone to look for a response on, is reduced to just 8
values in the expectation that an 8-way multiplexer will use less
logic than one with more than 8 inputs.

With this timing is considerably better on the A7-100T.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
1 year ago
Anton Blanchard af6bc48d36
Merge pull request #329 from paulusmack/wb-fix
Wishbone addressing fix
2 years ago
Paul Mackerras ca4eb46aea Make wishbone addresses be in units of doublewords or words
This makes the 64-bit wishbone buses have the address expressed in
units of doublewords (64 bits), and similarly for the 32-bit buses the
address is in units of words (32 bits).  This is to comply with the
wishbone spec.  Previously the addresses on the wishbone buses were in
units of bytes regardless of the bus data width, which is not correct
and caused problems with interfacing with externally-generated logic.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2 years ago
Paul Mackerras 734e4c4a52 core: Add a short multiplier
This adds an optional 16 bit x 16 bit signed multiplier and uses it
for multiply instructions that return the low 64 bits of the product
(mull[dw][o] and mulli, but not maddld) when the operands are both in
the range -2^15 .. 2^15 - 1.   The "short" 16-bit multiplier produces
its result combinatorially, so a multiply that uses it executes in one
cycle.  This improves the coremark result by about 4%, since coremark
does quite a lot of multiplies and they almost all have operands that
fit into 16 bits.

The presence of the short multiplier is controlled by a generic at the
execute1, SOC, core and top levels.  For now, it defaults to off for
all platforms, and can be enabled using the --has_short_mult flag to
fusesoc.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2 years ago
Anton Blanchard 591e96d1a2 gpio: Add HAS_GPIO to avoid verilator build errors
The verilator build fails with warnings and errors, because NGPIO
is 0 and we do things like:

        gpio_out : out std_ulogic_vector(NGPIO - 1 downto 0);

Set NGPIO to something reasonable (eg 32) and add HAS_GPIO to avoid
building the macro entirely if it isn't in use.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
2 years ago
Michael Neuling 84473eda1b Merge pull request #277 from paulus/gpio
A few cleanups. GPIO IRQ number is now 4 as 3 is now taken by the SD card.
2 years ago
Paul Mackerras 21ed730514 arty_a7: Add litesdcard interface
This adds litesdcard.v generated from the litex/litesdcard project,
along with logic in top-arty.vhdl to connect it into the system.
There is now a DMA wishbone coming in to soc.vhdl which is narrower
than the other wishbone masters (it has 32-bit data rather than
64-bit) so there is a widening/narrowing adapter between it and the
main wishbone master arbiter.

Also, litesdcard generates a non-pipelined wishbone for its DMA
connection, which needs to be converted to a pipelined wishbone.  We
have a latch on both the incoming and outgoing sides of the wishbone
in order to help make timing (at the cost of two extra cycles of
latency).

litesdcard generates an interrupt signal which is wired up to input 3
of the ICS (IRQ 19).

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2 years ago
Paul Mackerras eb7eba2d92 dcache: Snoop writes to memory by other agents
This adds a path where the wishbone that goes out to memory and I/O
also gets fed back to the dcache, which looks for writes that it
didn't initiate, and invalidates any cache line that gets written to.

This involves a second read port on the cache tag RAM for looking up
the snooped writes, and effectively a second write port on the cache
valid bit array to clear bits corresponding to snoop hits.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2 years ago
Anton Blanchard 5cc5d8f030
Merge pull request #281 from antonblanchard/cache-tlb-parameters
Pass icache/dcache/tlb parameters down from soc
2 years ago
Anton Blanchard 91a53d8001 Allow SPI BOOT_CLOCKS to be overridden by top level
Our SPI controller sends 8 dummy clocks at boot which Ben
added for some Xilinx boards. This should be harmless but
it is confusing the flash testbench in the Caravel project.

Add a parameter so it can be overridden at the top level.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
2 years ago
Anton Blanchard 2d21b95f87 Pass icache/dcache/tlb parameters down from soc
We want much smaller caches and tlbs when building for sky130, so
allow the toplevel file to override the defaults.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
2 years ago
Paul Mackerras f06ffcf9b7 Add a GPIO controller and use it to drive the shield I/O pins on the Arty
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>
2 years ago
Michael Neuling 9a6a7e9fe5
Merge pull request #268 from paulusmack/btc
Implement branch target cache
2 years ago
Anton Blanchard 481f3cdfea Add some wishbone checking
Check that stb, cyc and ack are never undefined. While not really needed
here, this also tests if --pragma synthesis_off/--pragma synthesis_on
works on all the tools we use.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
2 years ago
Paul Mackerras 0fb207be60 fetch1: Implement a simple branch target cache
This implements a cache in fetch1, where each entry stores the address
of a simple branch instruction (b or bc) and the target of the branch.
When fetching sequentially, if the address being fetched matches the
cache entry, then fetching will be redirected to the branch target.
The cache has 1024 entries and is direct-mapped, i.e. indexed by bits
11..2 of the NIA.

The bus from execute1 now carries information about taken and
not-taken simple branches, which fetch1 uses to update the cache.
The cache entry is updated for both taken and not-taken branches, with
the valid bit being set if the branch was taken and cleared if the
branch was not taken.

If fetching is redirected to the branch target then that goes down the
pipe as a predicted-taken branch, and decode1 does not do any static
branch prediction.  If fetching is not redirected, then the next
instruction goes down the pipe as normal and decode1 does its static
branch prediction.

In order to make timing, the lookup of the cache is pipelined, so on
each cycle the cache entry for the current NIA + 8 is read.  This
means that after a redirect (from decode1 or execute1), only the third
and subsequent sequentially-fetched instructions will be able to be
predicted.

This improves the coremark value on the Arty A7-100 from about 180 to
about 190 (more than 5%).

The BTC is optional.  Builds for the Artix 7 35-T part have it off by
default because the extra ~1420 LUTs it takes mean that the design
doesn't fit on the Arty A7-35 board.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2 years ago
Paul Mackerras 97586e7e99 soc: Drive uart1_irq to 0 when we don't have UART1
The tools complain about uart1_irq not being driven and not having a
default when HAS_UART1 is false.  This sets it to 0 in that case.

Fixes: 7575b1e0c2 ("uart: Import and hook up opencore 16550 compatible UART")
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2 years ago
Paul Mackerras 45cd8f4fc3 core: Add support for floating-point loads and stores
This extends the register file so it can hold FPR values, and
implements the FP loads and stores that do not require conversion
between single and double precision.

We now have the FP, FE0 and FE1 bits in MSR.  FP loads and stores
cause a FP unavailable interrupt if MSR[FP] = 0.

The FPU facilities are optional and their presence is controlled by
the HAS_FPU generic passed down from the top-level board file.  It
defaults to true for all except the A7-35 boards.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Benjamin Herrenschmidt fb5c16d05e uart: Make 16550 the default
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 7575b1e0c2 uart: Import and hook up opencore 16550 compatible UART
This imports via fusesoc a 16550 compatible (ie "standard") UART,
and wires it up optionally in the SoC instead of the potato one.

This also adds support for a second UART (which is always a
16550) to Arty, wired to JC "bottom" port.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 8366710217 liteeth: Hook up LiteX LiteEth ethernet controller
Currently only generated for Arty.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt bb54af59de xics: Add support for reduced priority field size
This makes the ICS support less than the 8 architected bits
and sets the soc to use 3 bits by default.

All the supported bits set translates to "masked" (and will read
back at 0xff), any small value is used as-is.

Linux doesn't use priorities above 5, so this is a way to save
silicon. The number of supported priority bits is exposed to the
OS via the config register.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 5c2fc47e2c xics: Add simple ICS
Move the external interrupt generation to a separate module
"ICS" (source controller) which a register per source containing
currently only the priority control.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Michael Neuling b90a0a2139
Merge pull request #208 from paulusmack/faster
Make the core go faster

Several major improvements in here:
- Simple branch predictor
- Reduced latency for mispredicted branches and interrupts by removing fetch2 stage
- Cache improvements
  o Request critical dword first on refill
  o Handle hits while refilling, including on line being refilled
  o Sizes doubled for both D and I
- Loadstore improvements: can now do one load or store every two cycles in most cases
- Optimized 2-cycle multiplier for Xilinx 7-series parts using DSP slices
- Timing improvements, including:
  o Stash buffer in decode1
  o Reduced width of execute1 result mux
  o Improved SPR decode in decode1
  o Some non-critical operation take a cycle longer so we can break some long combinatorial chains
- Core logging: logs 256 bits of info every cycle into a ring buffer, to help with debugging and performance analysis

This increases the LUT usage for the "synth" + A35 target from 9182 to 10297 = 12%.
3 years ago
Paul Mackerras 78de4fef72 Make LOG_LENGTH configurable per FPGA variant
This plumbs the LOG_LENGTH parameter (which controls how many entries
the core log RAM has) up to the top level so that it can be set on
the fusesoc command line and have different default values on
different FPGAs.

It now defaults to 512 entries generally and on the Artix-7 35 parts,
and 2048 on the larger Artix-7 FPGAs.  It can be set to 0 if desired.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Benjamin Herrenschmidt 67b6117ebf soc: Slight cleanup of IRQ assignments
Use a separate process to assign selected interrupts to the
interrupt array, and document them.

There's only one interrupt *for now* but that will change
and this way is clearer.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt e07b3dd6fa soc: Rename uart_dat8 to uart0_dat8
Just for consistency. Will come in handy if we ever add a second one

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt f9f18906a3 soc: Rename wb_dram_ctrl to wb_ext_io and rework decoding
This makes the control bus currently going out of "soc" towards
litedram more generic for external IO devices added by the
top-level rather than inside the SoC proper.

This is mostly renaming of signals and a small change on how the
address decoder operates, using a separate "cascaded" decode for
the external IOs.

We make the region 0xc8nn_nnnn be the "external IO" region for
now.

This will make it easier / cleaner to add more external devices.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt bf7def5503 soc: Don't require dram wishbones signals to be wired by toplevel
Currently, when not using litedram, the top level still has to hook
up "dummy" wishbones to the main dram and control dram busses coming
out of the SoC and provide ack signals.

Instead, make the SoC generate the acks internally when not using
litedram and use defaults to make the wiring entirely optional.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 1ffc89e58b soc: Add defaults for some input signals
That way the top-level's don't need to assign them

Also remove generics that are set to the default anyways

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 4244b54984 soc: Remove unused RESET_LOW generic
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 6c3a8bf417 bram: Remove combinational loop on stall
It hurts timing and is pointless

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt e5aa0e9dc9 uart: Remove combinational loops on ack and stall signal
They hurt timing forcing signals to come from the master and back
again in one cycle. Stall isn't sampled by the master unless there
is an active cycle so masking it with cyc is pointless. Masking acks
is somewhat pointless too as we don't handle early dropping of cyc
in any of our slaves properly anyways.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt cc4dcb3597 spi: Add SPI Flash controller
This adds an SPI flash controller which supports direct
memory-mapped access to the flash along with a manual
mode to send commands.

The direct mode can be set via generic to default to single
wire or quad mode. The controller supports normal, dual and quad
accesses with configurable commands, clock divider, dummy clocks
etc...

The SPI clock can be an even divider of sys_clk starting at 2
(so max 50Mhz with our typical Arty designs).

A flash offset is carried via generics to syscon to tell SW about
which portion of the flash is reserved for the FPGA bitfile. There
is currently no plumbing to make the CPU reset past that address (TBD).

Note: Operating at 50Mhz has proven unreliable without adding some
delay to the sampling of the input data. I'm working in improving
this, in the meantime, I'm leaving the default set at 25 Mhz.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt bf1b98b958 litedram: Add support for booting without BRAM
This adds an option to disable the main BRAM and instead copy a
payload stashed along with the init code in the secondary BRAM
into DRAM and boot from there

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt f86fb74bfe irq: Simplify xics->core irq input
Use a simple wire. common.vhdl types are better kept for things
local to the core. We can add more wires later if we need to for
HV irqs etc...

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 573b6b4bc4 soc: Rework interconnect
This changes the SoC interconnect such that the main 64-bit wishbone out
of the processor is first split between only 3 slaves (BRAM, DRAM and a
general "IO" bus) instead of all the slaves in the SoC.

The IO bus leg is then latched and down-converted to 32 bits data width,
before going through a second address decoder for the various IO devices.

This significantly reduces routing and timing pressure on the main bus,
allowing to get rid of frequent timing violations when synthetizing on
small'ish FPGAs such as the Artix-7 35T found on the original Arty board.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt 8d64090a68 sw: Add full memory map to .h and use it for litedram .lds
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Anton Blanchard 4e78b8078e
Merge branch 'master' into litedram 3 years ago
Benjamin Herrenschmidt acbdd396a5 soc/core: Add reset latches
This adds one-cycle latches to the various resets out of the soc and
into the various core modules. It *seems* to help vivado P&R a bit
and has shown to avoid timing violations under some circumstances.

Interestingly those resets never seem to appear in the bad timing
path. It looks like those long resets simply impose placement
constraints that Vivado satisfies at the expense of timing elsewhere.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Benjamin Herrenschmidt c19b5b8cc7 litedram: Update to new LiteX/LiteDRAM version
Things have changed a bit in upstream LiteX. LiteDRAM now exposes a
wishbone for the CSRs for example.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
3 years ago
Paul Mackerras 941499133e soc: Work around compile error with ghdl 0.37-dev
The ghdl packaged in Fedora 31 doesn't like a port map of the form
"rst => rst or core_reset", so this works around the problem by
doing the OR in a separate statement.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
3 years ago
Benjamin Herrenschmidt 7f1f6b8525 litedram: Add support for Microwatt-initialized controller
This adds support for initializing the memory controller from microwatt
rather than using a built-in RiscV processor. This might require some
fixes to LiteX and LiteDRAM (they haven't been merged as of this commit
yet).

This is enabled in the shipped generated files and can be changed via
modifying the generator script to pass False to "mw_init"

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