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

1 files changed, 162 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/riscv/cpus.txt b/Documentation/devicetree/bindings/riscv/cpus.txt
new file mode 100644
index 000000000000..adf7b7af5dc3
--- /dev/null
+++ b/Documentation/devicetree/bindings/riscv/cpus.txt
@@ -0,0 +1,162 @@
+===================
+RISC-V CPU Bindings
+===================
+
+The device tree allows to describe the layout of CPUs in a system through
+the "cpus" node, which in turn contains a number of subnodes (ie "cpu")
+defining properties for every cpu.
+
+Bindings for CPU nodes follow the Devicetree Specification, available from:
+
+https://www.devicetree.org/specifications/
+
+with updates for 32-bit and 64-bit RISC-V systems provided in this document.
+
+===========
+Terminology
+===========
+
+This document uses some terminology common to the RISC-V community that is not
+widely used, the definitions of which are listed here:
+
+* hart: A hardware execution context, which contains all the state mandated by
+  the RISC-V ISA: a PC and some registers.  This terminology is designed to
+  disambiguate software's view of execution contexts from any particular
+  microarchitectural implementation strategy.  For example, my Intel laptop is
+  described as having one socket with two cores, each of which has two hyper
+  threads.  Therefore this system has four harts.
+
+=====================================
+cpus and cpu node bindings definition
+=====================================
+
+The RISC-V architecture, in accordance with the Devicetree Specification,
+requires the cpus and cpu nodes to be present and contain the properties
+described below.
+
+- cpus node
+
+        Description: Container of cpu nodes
+
+        The node name must be "cpus".
+
+        A cpus node must define the following properties:
+
+        - #address-cells
+                Usage: required
+                Value type: <u32>
+                Definition: must be set to 1
+        - #size-cells
+                Usage: required
+                Value type: <u32>
+                Definition: must be set to 0
+
+- cpu node
+
+        Description: Describes a hart context
+
+        PROPERTIES
+
+        - device_type
+                Usage: required
+                Value type: <string>
+                Definition: must be "cpu"
+        - reg
+                Usage: required
+                Value type: <u32>
+                Definition: The hart ID of this CPU node
+        - compatible:
+                Usage: required
+                Value type: <stringlist>
+                Definition: must contain "riscv", may contain one of
+                            "sifive,rocket0"
+        - mmu-type:
+                Usage: optional
+                Value type: <string>
+                Definition: Specifies the CPU's MMU type.  Possible values are
+                            "riscv,sv32"
+                            "riscv,sv39"
+                            "riscv,sv48"
+        - riscv,isa:
+                Usage: required
+                Value type: <string>
+                Definition: Contains the RISC-V ISA string of this hart.  These
+                            ISA strings are defined by the RISC-V ISA manual.
+
+Example: SiFive Freedom U540G Development Kit
+---------------------------------------------
+
+This system contains two harts: a hart marked as disabled that's used for
+low-level system tasks and should be ignored by Linux, and a second hart that
+Linux is allowed to run on.
+
+        cpus {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                timebase-frequency = <1000000>;
+                cpu@0 {
+                        clock-frequency = <1600000000>;
+                        compatible = "sifive,rocket0", "riscv";
+                        device_type = "cpu";
+                        i-cache-block-size = <64>;
+                        i-cache-sets = <128>;
+                        i-cache-size = <16384>;
+                        next-level-cache = <&L15 &L0>;
+                        reg = <0>;
+                        riscv,isa = "rv64imac";
+                        status = "disabled";
+                        L10: interrupt-controller {
+                                #interrupt-cells = <1>;
+                                compatible = "riscv,cpu-intc";
+                                interrupt-controller;
+                        };
+                };
+                cpu@1 {
+                        clock-frequency = <1600000000>;
+                        compatible = "sifive,rocket0", "riscv";
+                        d-cache-block-size = <64>;
+                        d-cache-sets = <64>;
+                        d-cache-size = <32768>;
+                        d-tlb-sets = <1>;
+                        d-tlb-size = <32>;
+                        device_type = "cpu";
+                        i-cache-block-size = <64>;
+                        i-cache-sets = <64>;
+                        i-cache-size = <32768>;
+                        i-tlb-sets = <1>;
+                        i-tlb-size = <32>;
+                        mmu-type = "riscv,sv39";
+                        next-level-cache = <&L15 &L0>;
+                        reg = <1>;
+                        riscv,isa = "rv64imafdc";
+                        status = "okay";
+                        tlb-split;
+                        L13: interrupt-controller {
+                                #interrupt-cells = <1>;
+                                compatible = "riscv,cpu-intc";
+                                interrupt-controller;
+                        };
+                };
+        };
+
+Example: Spike ISA Simulator with 1 Hart
+----------------------------------------
+
+This device tree matches the Spike ISA golden model as run with `spike -p1`.
+
+        cpus {
+                cpu@0 {
+                        device_type = "cpu";
+                        reg = <0x00000000>;
+                        status = "okay";
+                        compatible = "riscv";
+                        riscv,isa = "rv64imafdc";
+                        mmu-type = "riscv,sv48";
+                        clock-frequency = <0x3b9aca00>;
+                        interrupt-controller {
+                                #interrupt-cells = <0x00000001>;
+                                interrupt-controller;
+                                compatible = "riscv,cpu-intc";
+                        }
+                }
+        }