Merge tag 'riscv-for-linus-4.15-arch-v9-premerge' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/linux
Pull RISC-V architecture support from Palmer Dabbelt:
"This contains the core RISC-V Linux port, which has been through nine
rounds of review on various mailing lists. The port is not complete:
there's some cleanup patches moving through the review process, a
whole bunch of drivers that need some work, and a lot of feature
additions that will be needed.
The patches contained in this tag have been through nine rounds of
review on the various mailing lists. I have some outstanding cleanup
patches, but since there's been so much review on these patches I
thought it would be best to submit them as-is and then submit explicit
cleanup patches so everyone can review them. This first patch set is
big enough that it's a bit of a pain to constantly rewrite, and it's
caused a few headaches with various contributors.
The port is definately a work in progress. While what's there builds
and boots with 4.14, it's a bit hard to actually see anything happen
because there are no device drivers yet. I maintain a staging branch
that contains all the device drivers and cleanup that actually works,
but those patches won't all be ready for a while. I'd like to get what
we currently have into your tree so everyone can start working from a
single base -- of particular importance is allowing the glibc
upstreaming process to proceed so we can sort out any possibly
lingering user-visible ABI problems we might have.
Copied below is the ChangeLog that contains the history of this patch
set:
(v9) As per suggestions on our v8 patch set, I've split the core
architecture code out from our drivers and would like to submit
this patch set to be included into linux-next, with the goal
being to be merged in during the next merge window. This patch
set is based on 4.14-rc2, but if it's better to have it based on
something else then I can change it around.
This patch set contains just the core arch code for RISC-V, so
while it builds an nominally boots, you can't print or take an
interrupt so it's not that useful. If you're looking to actually
boot a system it would probably be better to use the full patch
set listed below.
We've collected a handful of tags from reviewers, and the
remainder of the patch set only got minimal feedback last time.
Here's what changed:
- We now use the device tree to initialize the timer driver so
it's less tighly coupled with the arch port.
- I cleaned up the defconfigs -- there's actually now just one,
and it's empty. For now I think we're OK with what the kernel
sets as defaults, but I anticipate we'll begin to expand this
as people start to use the port more.
- The VDSO symbols version is sane.
- We WFI while spinning in the boot loop.
- A handful of comments have been added.
While there are still a handful of FIXMEs in this patch set,
we've started to get enough interest from various users and
contributors that maintaining an out of tree patch set is
starting to become a big burden. Hopefully the patches are good
enough to merge now, which will at least get everyone working in
a more reasonable manner as we clean up the remaining issues.
(v8) I know it may not be the ideal time to submit a patch set right
now, as it's the middle of the merge window, but things have
calmed down quite a bit in the last month so I thought it would
be good to get everyone on the same page. There's been a handful
of changes since the last patch set, but most of them are fairly
minor:
- We changed PAGE_OFFSET to allowing mapping more physical
memory on 64-bit systems. This is user configurable, as it
triggers a different code model that generates slightly less
efficient code.
- The device tree binding documentation is back, I'd managed to
lose it at some point.
- We now pass the atomic64 test suite
- The SBI timer driver has been refactored.
(v7) It's been a while since my last patch set, but the changes han
been fairly minimal:
- The PCI cleanup patches have been dropped, we'll do them as a
separate patch set later.
- We've the Kconfig entries from CONFIG_ISA_* to
CONFIG_RISCV_ISA_*, to make grep easier.
- There have been a handful of memory model related tweaks in
I/O land, particularly relating the PCI and the upcoming
platform specification. There are significant comments in the
relevant files. This is still a WIP, but I think we're close
to getting as good as we're going to get until we end up with
some more specifications.
(v6) As it's been only a day since the v5 patch set, the changes are
pretty minimal:
- The patch set is now based on linux-next/master, which I
believe is a better base now that we're getting closer to
upstream.
- EARLY_PRINTK is no longer an option. Since the SBI console is
reasonable, there's no penalty to enabling it (and thus no
benefit to disabling it).
- The mmap syscalls were refactored a bit.
(v5) Things have really started to calm down, so this is fairly
similar to the v4 patch set. The most interesting changes
include:
- We've moved back to a single patch set.
- SMP support has been fixed, I was accidentally running on a
non-SMP configuration. There were various mistakes all over
the tree as a result of this.
- The cmpxchg syscalls have been removed, as they were deemed a
bad idea. As a result, RISC-V Linux systems mandate the A
extension. The corresponding Kconfig entry to enable builds
on non-A systems has been removed.
- A few more atomic fixes: mostly fence changes, but those
resulted in a handful of additional macros that were no
longer necessary.
- riscv_early_sie has been removed.
(v4) There have only been a few changes since the v3 patch set:
- The cmpxchg64 syscall is no longer enabled on 32-bit systems.
It's not possible to provide this on SMP systems, and it's
not necessary as glibc knows not to call it.
- We provide a ELF_HWCAP so users can determine the ISA of the
machine the kernel is running on.
- The multi-line comments are in a better form.
- There were a handful of headers that could be replaced with
the asm-generic versions, and a few unnecessary definitions.
- We no longer use printk, but instead use pr_*.
- A few Kconfig and defconfig entries have been cleaned up.
(v3) A highlight of the changes since the v2 patch set includes:
- We've split out all our drivers into separate patch sets,
which I've already sent out to the relevant maintainers. I
haven't included those patches in this patch set, but some of
them are necessary to build our port.
- The patch set is now split up differently: rather than being
split per directory it is split per topic. Hopefully this
will make it easier to review the port on the mailing list.
The split is a bit rough, so you probably still want to look
at the patch set as a whole.
- atomic.h has been completely rewritten and is hopefully now
correct. I've attempted to sanitize the various other memory
model related code as well, and I think it should all be sane
now aside from a handful of FIXMEs commented in the code.
- We've changed the cmpexchg syscall to always exist and to not
be multiplexed. There is also a VDSO entry for compare and
exchange, which allows kernels with the A extension to
execute user code without the A extension reasonably fast.
- Our user-visible register state now contains enough space for
the Q extension for 128-bit floating point, as well as a few
words to allow extensibility to future ISA extensions like
the eventual V extension for vectors.
- A handful of driver cleanups, but these have been split into
separate patch sets now so I won't duplicate them here.
(v2) A highlight of the changes since the v1 patch set includes:
- We've split out our drivers into the right places, which
means now there's a lot more patches. I'll be submitting
these patches to various subsystem maintainers and including
them in any future RISC-V patch sets until they've been
merged.
- The SBI console driver has been completely rewritten to use
the HVC helpers and is now significantly smaller.
- We've begun to use weaker barriers as opposed to just the big
"fence". There's still some work to do here, specifically:
- We need fences in the relaxed MMIO functions.
- The non-relaxed MMIO functions are missing R/W bits on their fences.
- Many AMOs need the aq and rl bits set.
- We now have thread_info in task_struct. As a result, sscratch
now contains TP instead of SP. This was necessary because
thread_info is no longer on the stack.
- A few shared routines have been added that we use instead of
creating another arch copy"
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
* tag 'riscv-for-linus-4.15-arch-v9-premerge' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/linux:
RISC-V: Build Infrastructure
RISC-V: User-facing API
RISC-V: Paging and MMU
RISC-V: Device, timer, IRQs, and the SBI
RISC-V: Task implementation
RISC-V: ELF and module implementation
RISC-V: Generic library routines and assembly
RISC-V: Atomic and Locking Code
RISC-V: Init and Halt Code
dt-bindings: RISC-V CPU Bindings
lib: Add shared copies of some GCC library routines
MAINTAINERS: Add RISC-V
This commit is contained in:
Linus Torvalds
162
Documentation/devicetree/bindings/riscv/cpus.txt
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162
Documentation/devicetree/bindings/riscv/cpus.txt
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===================
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RISC-V CPU Bindings
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===================
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The device tree allows to describe the layout of CPUs in a system through
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the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
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defining properties for every cpu.
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Bindings for CPU nodes follow the Devicetree Specification, available from:
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https://www.devicetree.org/specifications/
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with updates for 32-bit and 64-bit RISC-V systems provided in this document.
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===========
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Terminology
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===========
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This document uses some terminology common to the RISC-V community that is not
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widely used, the definitions of which are listed here:
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* hart: A hardware execution context, which contains all the state mandated by
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the RISC-V ISA: a PC and some registers. This terminology is designed to
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disambiguate software's view of execution contexts from any particular
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microarchitectural implementation strategy. For example, my Intel laptop is
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described as having one socket with two cores, each of which has two hyper
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threads. Therefore this system has four harts.
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=====================================
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cpus and cpu node bindings definition
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=====================================
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The RISC-V architecture, in accordance with the Devicetree Specification,
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requires the cpus and cpu nodes to be present and contain the properties
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described below.
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- cpus node
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Description: Container of cpu nodes
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The node name must be "cpus".
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A cpus node must define the following properties:
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- #address-cells
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Usage: required
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Value type: <u32>
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Definition: must be set to 1
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- #size-cells
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Usage: required
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Value type: <u32>
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Definition: must be set to 0
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- cpu node
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Description: Describes a hart context
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PROPERTIES
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- device_type
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Usage: required
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Value type: <string>
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Definition: must be "cpu"
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- reg
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Usage: required
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Value type: <u32>
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Definition: The hart ID of this CPU node
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- compatible:
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Usage: required
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Value type: <stringlist>
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Definition: must contain "riscv", may contain one of
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"sifive,rocket0"
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- mmu-type:
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Usage: optional
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Value type: <string>
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Definition: Specifies the CPU's MMU type. Possible values are
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"riscv,sv32"
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"riscv,sv39"
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"riscv,sv48"
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- riscv,isa:
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Usage: required
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Value type: <string>
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Definition: Contains the RISC-V ISA string of this hart. These
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ISA strings are defined by the RISC-V ISA manual.
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Example: SiFive Freedom U540G Development Kit
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---------------------------------------------
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This system contains two harts: a hart marked as disabled that's used for
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low-level system tasks and should be ignored by Linux, and a second hart that
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Linux is allowed to run on.
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cpus {
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#address-cells = <1>;
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#size-cells = <0>;
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timebase-frequency = <1000000>;
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cpu@0 {
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clock-frequency = <1600000000>;
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compatible = "sifive,rocket0", "riscv";
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device_type = "cpu";
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i-cache-block-size = <64>;
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i-cache-sets = <128>;
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i-cache-size = <16384>;
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next-level-cache = <&L15 &L0>;
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reg = <0>;
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riscv,isa = "rv64imac";
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status = "disabled";
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L10: interrupt-controller {
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#interrupt-cells = <1>;
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compatible = "riscv,cpu-intc";
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interrupt-controller;
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};
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};
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cpu@1 {
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clock-frequency = <1600000000>;
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compatible = "sifive,rocket0", "riscv";
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d-cache-block-size = <64>;
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d-cache-sets = <64>;
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d-cache-size = <32768>;
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d-tlb-sets = <1>;
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d-tlb-size = <32>;
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device_type = "cpu";
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i-cache-block-size = <64>;
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i-cache-sets = <64>;
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i-cache-size = <32768>;
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i-tlb-sets = <1>;
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i-tlb-size = <32>;
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mmu-type = "riscv,sv39";
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next-level-cache = <&L15 &L0>;
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reg = <1>;
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riscv,isa = "rv64imafdc";
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status = "okay";
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tlb-split;
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L13: interrupt-controller {
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#interrupt-cells = <1>;
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compatible = "riscv,cpu-intc";
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interrupt-controller;
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};
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};
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};
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Example: Spike ISA Simulator with 1 Hart
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----------------------------------------
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This device tree matches the Spike ISA golden model as run with `spike -p1`.
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cpus {
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cpu@0 {
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device_type = "cpu";
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reg = <0x00000000>;
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status = "okay";
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compatible = "riscv";
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riscv,isa = "rv64imafdc";
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mmu-type = "riscv,sv48";
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clock-frequency = <0x3b9aca00>;
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interrupt-controller {
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#interrupt-cells = <0x00000001>;
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interrupt-controller;
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compatible = "riscv,cpu-intc";
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}
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}
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}
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