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, 110 insertions, 0 deletions

diff --git a/arch/riscv/lib/delay.c b/arch/riscv/lib/delay.c
new file mode 100644
index 000000000000..1cc4ac3964b4
--- /dev/null
+++ b/arch/riscv/lib/delay.c
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   This program is free software; you can redistribute it and/or
+ *   modify it under the terms of the GNU General Public License
+ *   as published by the Free Software Foundation, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#include <linux/delay.h>
+#include <linux/param.h>
+#include <linux/timex.h>
+#include <linux/export.h>
+
+/*
+ * This is copies from arch/arm/include/asm/delay.h
+ *
+ * Loop (or tick) based delay:
+ *
+ * loops = loops_per_jiffy * jiffies_per_sec * delay_us / us_per_sec
+ *
+ * where:
+ *
+ * jiffies_per_sec = HZ
+ * us_per_sec = 1000000
+ *
+ * Therefore the constant part is HZ / 1000000 which is a small
+ * fractional number. To make this usable with integer math, we
+ * scale up this constant by 2^31, perform the actual multiplication,
+ * and scale the result back down by 2^31 with a simple shift:
+ *
+ * loops = (loops_per_jiffy * delay_us * UDELAY_MULT) >> 31
+ *
+ * where:
+ *
+ * UDELAY_MULT = 2^31 * HZ / 1000000
+ *             = (2^31 / 1000000) * HZ
+ *             = 2147.483648 * HZ
+ *             = 2147 * HZ + 483648 * HZ / 1000000
+ *
+ * 31 is the biggest scale shift value that won't overflow 32 bits for
+ * delay_us * UDELAY_MULT assuming HZ <= 1000 and delay_us <= 2000.
+ */
+#define MAX_UDELAY_US	2000
+#define MAX_UDELAY_HZ	1000
+#define UDELAY_MULT	(2147UL * HZ + 483648UL * HZ / 1000000UL)
+#define UDELAY_SHIFT	31
+
+#if HZ > MAX_UDELAY_HZ
+#error "HZ > MAX_UDELAY_HZ"
+#endif
+
+/*
+ * RISC-V supports both UDELAY and NDELAY.  This is largely the same as above,
+ * but with different constants.  I added 10 bits to the shift to get this, but
+ * the result is that I need a 64-bit multiply, which is slow on 32-bit
+ * platforms.
+ *
+ * NDELAY_MULT = 2^41 * HZ / 1000000000
+ *             = (2^41 / 1000000000) * HZ
+ *             = 2199.02325555 * HZ
+ *             = 2199 * HZ + 23255550 * HZ / 1000000000
+ *
+ * The maximum here is to avoid 64-bit overflow, but it isn't checked as it
+ * won't happen.
+ */
+#define MAX_NDELAY_NS   (1ULL << 42)
+#define MAX_NDELAY_HZ	MAX_UDELAY_HZ
+#define NDELAY_MULT	((unsigned long long)(2199ULL * HZ + 23255550ULL * HZ / 1000000000ULL))
+#define NDELAY_SHIFT	41
+
+#if HZ > MAX_NDELAY_HZ
+#error "HZ > MAX_NDELAY_HZ"
+#endif
+
+void __delay(unsigned long cycles)
+{
+	u64 t0 = get_cycles();
+
+	while ((unsigned long)(get_cycles() - t0) < cycles)
+		cpu_relax();
+}
+
+void udelay(unsigned long usecs)
+{
+	unsigned long ucycles = usecs * lpj_fine * UDELAY_MULT;
+
+	if (unlikely(usecs > MAX_UDELAY_US)) {
+		__delay((u64)usecs * riscv_timebase / 1000000ULL);
+		return;
+	}
+
+	__delay(ucycles >> UDELAY_SHIFT);
+}
+EXPORT_SYMBOL(udelay);
+
+void ndelay(unsigned long nsecs)
+{
+	/*
+	 * This doesn't bother checking for overflow, as it won't happen (it's
+	 * an hour) of delay.
+	 */
+	unsigned long long ncycles = nsecs * lpj_fine * NDELAY_MULT;
+	__delay(ncycles >> NDELAY_SHIFT);
+}
+EXPORT_SYMBOL(ndelay);