arch/tile: core support for Tilera 32-bit chips.

This change is the core kernel support for TILEPro and TILE64 chips.
No driver support (except the console driver) is included yet.

This includes the relevant Linux headers in asm/; the low-level
low-level "Tile architecture" headers in arch/, which are
shared with the hypervisor, etc., and are build-system agnostic;
and the relevant hypervisor headers in hv/.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reviewed-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 274 insertions, 0 deletions

diff --git a/arch/tile/lib/memset_32.c b/arch/tile/lib/memset_32.c
new file mode 100644
index 000000000000..8593bc82398a
--- /dev/null
+++ b/arch/tile/lib/memset_32.c
@@ -0,0 +1,274 @@
+/*
+ * Copyright 2010 Tilera Corporation. All Rights Reserved.
+ *
+ *   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, GOOD TITLE or
+ *   NON INFRINGEMENT.  See the GNU General Public License for
+ *   more details.
+ */
+
+#include <arch/chip.h>
+
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/module.h>
+
+
+void *memset(void *s, int c, size_t n)
+{
+        uint32_t *out32;
+        int n32;
+        uint32_t v16, v32;
+        uint8_t *out8 = s;
+#if !CHIP_HAS_WH64()
+        int ahead32;
+#else
+        int to_align32;
+#endif
+
+        /* Experimentation shows that a trivial tight loop is a win up until
+         * around a size of 20, where writing a word at a time starts to win.
+         */
+#define BYTE_CUTOFF 20
+
+#if BYTE_CUTOFF < 3
+        /* This must be at least at least this big, or some code later
+         * on doesn't work.
+         */
+#error "BYTE_CUTOFF is too small"
+#endif
+
+        if (n < BYTE_CUTOFF) {
+                /* Strangely, this turns out to be the tightest way to
+                 * write this loop.
+                 */
+                if (n != 0) {
+                        do {
+                                /* Strangely, combining these into one line
+                                 * performs worse.
+                                 */
+                                *out8 = c;
+                                out8++;
+                        } while (--n != 0);
+                }
+
+                return s;
+        }
+
+#if !CHIP_HAS_WH64()
+        /* Use a spare issue slot to start prefetching the first cache
+         * line early. This instruction is free as the store can be buried
+         * in otherwise idle issue slots doing ALU ops.
+         */
+        __insn_prefetch(out8);
+
+        /* We prefetch the end so that a short memset that spans two cache
+         * lines gets some prefetching benefit. Again we believe this is free
+         * to issue.
+         */
+        __insn_prefetch(&out8[n - 1]);
+#endif /* !CHIP_HAS_WH64() */
+
+
+        /* Align 'out8'. We know n >= 3 so this won't write past the end. */
+        while (((uintptr_t) out8 & 3) != 0) {
+                *out8++ = c;
+                --n;
+        }
+
+        /* Align 'n'. */
+        while (n & 3)
+                out8[--n] = c;
+
+        out32 = (uint32_t *) out8;
+        n32 = n >> 2;
+
+        /* Tile input byte out to 32 bits. */
+        v16 = __insn_intlb(c, c);
+        v32 = __insn_intlh(v16, v16);
+
+        /* This must be at least 8 or the following loop doesn't work. */
+#define CACHE_LINE_SIZE_IN_WORDS (CHIP_L2_LINE_SIZE() / 4)
+
+#if !CHIP_HAS_WH64()
+
+        ahead32 = CACHE_LINE_SIZE_IN_WORDS;
+
+        /* We already prefetched the first and last cache lines, so
+         * we only need to do more prefetching if we are storing
+         * to more than two cache lines.
+         */
+        if (n32 > CACHE_LINE_SIZE_IN_WORDS * 2) {
+                int i;
+
+                /* Prefetch the next several cache lines.
+                 * This is the setup code for the software-pipelined
+                 * loop below.
+                 */
+#define MAX_PREFETCH 5
+                ahead32 = n32 & -CACHE_LINE_SIZE_IN_WORDS;
+                if (ahead32 > MAX_PREFETCH * CACHE_LINE_SIZE_IN_WORDS)
+                        ahead32 = MAX_PREFETCH * CACHE_LINE_SIZE_IN_WORDS;
+
+                for (i = CACHE_LINE_SIZE_IN_WORDS;
+                     i < ahead32; i += CACHE_LINE_SIZE_IN_WORDS)
+                        __insn_prefetch(&out32[i]);
+        }
+
+        if (n32 > ahead32) {
+                while (1) {
+                        int j;
+
+                        /* Prefetch by reading one word several cache lines
+                         * ahead.  Since loads are non-blocking this will
+                         * cause the full cache line to be read while we are
+                         * finishing earlier cache lines.  Using a store
+                         * here causes microarchitectural performance
+                         * problems where a victimizing store miss goes to
+                         * the head of the retry FIFO and locks the pipe for
+                         * a few cycles.  So a few subsequent stores in this
+                         * loop go into the retry FIFO, and then later
+                         * stores see other stores to the same cache line
+                         * are already in the retry FIFO and themselves go
+                         * into the retry FIFO, filling it up and grinding
+                         * to a halt waiting for the original miss to be
+                         * satisfied.
+                         */
+                        __insn_prefetch(&out32[ahead32]);
+
+#if 1
+#if CACHE_LINE_SIZE_IN_WORDS % 4 != 0
+#error "Unhandled CACHE_LINE_SIZE_IN_WORDS"
+#endif
+
+                        n32 -= CACHE_LINE_SIZE_IN_WORDS;
+
+                        /* Save icache space by only partially unrolling
+                         * this loop.
+                         */
+                        for (j = CACHE_LINE_SIZE_IN_WORDS / 4; j > 0; j--) {
+                                *out32++ = v32;
+                                *out32++ = v32;
+                                *out32++ = v32;
+                                *out32++ = v32;
+                        }
+#else
+                        /* Unfortunately, due to a code generator flaw this
+                         * allocates a separate register for each of these
+                         * stores, which requires a large number of spills,
+                         * which makes this procedure enormously bigger
+                         * (something like 70%)
+                         */
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        *out32++ = v32;
+                        n32 -= 16;
+#endif
+
+                        /* To save compiled code size, reuse this loop even
+                         * when we run out of prefetching to do by dropping
+                         * ahead32 down.
+                         */
+                        if (n32 <= ahead32) {
+                                /* Not even a full cache line left,
+                                 * so stop now.
+                                 */
+                                if (n32 < CACHE_LINE_SIZE_IN_WORDS)
+                                        break;
+
+                                /* Choose a small enough value that we don't
+                                 * prefetch past the end.  There's no sense
+                                 * in touching cache lines we don't have to.
+                                 */
+                                ahead32 = CACHE_LINE_SIZE_IN_WORDS - 1;
+                        }
+                }
+        }
+
+#else /* CHIP_HAS_WH64() */
+
+        /* Determine how many words we need to emit before the 'out32'
+         * pointer becomes aligned modulo the cache line size.
+         */
+        to_align32 =
+                (-((uintptr_t)out32 >> 2)) & (CACHE_LINE_SIZE_IN_WORDS - 1);
+
+        /* Only bother aligning and using wh64 if there is at least
+         * one full cache line to process.  This check also prevents
+         * overrunning the end of the buffer with alignment words.
+         */
+        if (to_align32 <= n32 - CACHE_LINE_SIZE_IN_WORDS) {
+                int lines_left;
+
+                /* Align out32 mod the cache line size so we can use wh64. */
+                n32 -= to_align32;
+                for (; to_align32 != 0; to_align32--) {
+                        *out32 = v32;
+                        out32++;
+                }
+
+                /* Use unsigned divide to turn this into a right shift. */
+                lines_left = (unsigned)n32 / CACHE_LINE_SIZE_IN_WORDS;
+
+                do {
+                        /* Only wh64 a few lines at a time, so we don't
+                         * exceed the maximum number of victim lines.
+                         */
+                        int x = ((lines_left < CHIP_MAX_OUTSTANDING_VICTIMS())
+                                  ? lines_left
+                                  : CHIP_MAX_OUTSTANDING_VICTIMS());
+                        uint32_t *wh = out32;
+                        int i = x;
+                        int j;
+
+                        lines_left -= x;
+
+                        do {
+                                __insn_wh64(wh);
+                                wh += CACHE_LINE_SIZE_IN_WORDS;
+                        } while (--i);
+
+                        for (j = x * (CACHE_LINE_SIZE_IN_WORDS / 4); j != 0; j--) {
+                                *out32++ = v32;
+                                *out32++ = v32;
+                                *out32++ = v32;
+                                *out32++ = v32;
+                        }
+                } while (lines_left != 0);
+
+                /* We processed all full lines above, so only this many
+                 * words remain to be processed.
+                 */
+                n32 &= CACHE_LINE_SIZE_IN_WORDS - 1;
+        }
+
+#endif /* CHIP_HAS_WH64() */
+
+        /* Now handle any leftover values. */
+        if (n32 != 0) {
+                do {
+                        *out32 = v32;
+                        out32++;
+                } while (--n32 != 0);
+        }
+
+        return s;
+}
+EXPORT_SYMBOL(memset);