gpu: nvgpu: Implement a bitmap allocator

Implement a bitmap allocator for GPU use. This allocator is useful for
managing memory (or resource) regions where the buddy allocator is not
ideal. Some instances are small regions or where the resource management
must not make calls to the kernel's memory allocation routines (anything
that ultimately calls alloc_page()).

The code path where this avoidance of alloc_page() is most required is
the gpfifo submit path. In order to keep this routine fast and have
predicable time constraints no alloc_page() calls is necessary. The
buddy allocator does not work for this since every time a buddy is
allocated there is the possibility that a pair (or more) buddy structs
have to be made. These allocs could perhaps require a call into
alloc_page() if there is not enouch space in the kmem_cache slab for
the buddy structs.

Change-Id: Ia46fce62d4bdafcebbc153b21b515cb51641d241
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/1176446
Reviewed-by: Yu-Huan Hsu <yhsu@nvidia.com>

4 files changed, 519 insertions, 1 deletions

diff --git a/drivers/gpu/nvgpu/Makefile b/drivers/gpu/nvgpu/Makefile
index a9a0f92f..1cf2ea37 100644
--- a/drivers/gpu/nvgpu/Makefile
+++ b/drivers/gpu/nvgpu/Makefile
@@ -53,6 +53,7 @@ nvgpu-y := \
         gk20a/hal.o \
         gk20a/hal_gk20a.o \
         gk20a/gk20a_allocator.o \
+        gk20a/gk20a_allocator_bitmap.o \
         gk20a/gk20a_allocator_buddy.o \
         gk20a/cde_gk20a.o \
         gk20a/platform_gk20a_generic.o \
diff --git a/drivers/gpu/nvgpu/gk20a/bitmap_allocator_priv.h b/drivers/gpu/nvgpu/gk20a/bitmap_allocator_priv.h
new file mode 100644
index 00000000..053a6425
--- /dev/null
+++ b/drivers/gpu/nvgpu/gk20a/bitmap_allocator_priv.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2016, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef BITMAP_ALLOCATOR_PRIV_H
+#define BITMAP_ALLOCATOR_PRIV_H
+
+#include <linux/rbtree.h>
+
+struct gk20a_allocator;
+
+struct gk20a_bitmap_allocator {
+        struct gk20a_allocator *owner;
+
+        u64 base;                       /* Base address of the space. */
+        u64 length;                     /* Length of the space. */
+        u64 blk_size;                   /* Size that corresponds to 1 bit. */
+        u64 blk_shift;                  /* Bit shift to divide by blk_size. */
+        u64 num_bits;                   /* Number of allocatable bits. */
+        u64 bit_offs;                   /* Offset of bitmap. */
+
+        unsigned long *bitmap;          /* The actual bitmap! */
+        struct rb_root allocs;          /* Tree of outstanding allocations. */
+
+        u64 flags;
+
+        bool inited;
+
+        /* Statistics */
+        u64 nr_allocs;
+        u64 nr_fixed_allocs;
+        u64 bytes_alloced;
+        u64 bytes_freed;
+};
+
+struct gk20a_bitmap_alloc {
+        u64 base;
+        u64 length;
+        struct rb_node alloc_entry;     /* RB tree of allocations. */
+};
+
+static inline struct gk20a_bitmap_allocator *bitmap_allocator(
+        struct gk20a_allocator *a)
+{
+        return (struct gk20a_bitmap_allocator *)(a)->priv;
+}
+
+
+#endif
diff --git a/drivers/gpu/nvgpu/gk20a/gk20a_allocator.h b/drivers/gpu/nvgpu/gk20a/gk20a_allocator.h
index 5d6b9426..26612bf9 100644
--- a/drivers/gpu/nvgpu/gk20a/gk20a_allocator.h
+++ b/drivers/gpu/nvgpu/gk20a/gk20a_allocator.h
@@ -73,9 +73,35 @@ struct gk20a_allocator {
 };
 
 /*
- * Allocator flags.
+ * These are the available allocator flags.
+ *
+ *   GPU_ALLOC_GVA_SPACE
+ *
+ *     This flag makes sense for the buddy allocator only. It specifies that the
+ *     allocator will be used for managing a GVA space. When managing GVA spaces
+ *     special care has to be taken to ensure that allocations of similar PTE
+ *     sizes are placed in the same PDE block. This allows the higher level
+ *     code to skip defining both small and large PTE tables for every PDE. That
+ *     can save considerable memory for address spaces that have a lot of
+ *     allocations.
+ *
+ *   GPU_ALLOC_NO_ALLOC_PAGE
+ *
+ *     For any allocator that needs to manage a resource in a latency critical
+ *     path this flag specifies that the allocator should not use any kmalloc()
+ *     or similar functions during normal operation. Initialization routines
+ *     may still use kmalloc(). This prevents the possibility of long waits for
+ *     pages when using alloc_page(). Currently only the bitmap allocator
+ *     implements this functionality.
+ *
+ *     Also note that if you accept this flag then you must also define the
+ *     free_fixed() function. Since no meta-data is allocated to help free
+ *     allocations you need to keep track of the meta-data yourself (in this
+ *     case the base and length of the allocation as opposed to just the base
+ *     of the allocation).
  */
 #define GPU_ALLOC_GVA_SPACE             0x1
+#define GPU_ALLOC_NO_ALLOC_PAGE         0x2
 
 static inline void alloc_lock(struct gk20a_allocator *a)
 {
@@ -98,6 +124,13 @@ int  gk20a_buddy_allocator_init(struct gk20a_allocator *allocator,
                                 const char *name, u64 base, u64 size,
                                 u64 blk_size, u64 flags);
 
+/*
+ * Bitmap initializers.
+ */
+int gk20a_bitmap_allocator_init(struct gk20a_allocator *__a,
+                                const char *name, u64 base, u64 length,
+                                u64 blk_size, u64 flags);
+
 #define GPU_BALLOC_MAX_ORDER            31
 
 /*
diff --git a/drivers/gpu/nvgpu/gk20a/gk20a_allocator_bitmap.c b/drivers/gpu/nvgpu/gk20a/gk20a_allocator_bitmap.c
new file mode 100644
index 00000000..2ddabc62
--- /dev/null
+++ b/drivers/gpu/nvgpu/gk20a/gk20a_allocator_bitmap.c
@@ -0,0 +1,423 @@
+/*
+ * Copyright (c) 2016, NVIDIA CORPORATION.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/bitops.h>
+
+#include "gk20a_allocator.h"
+#include "bitmap_allocator_priv.h"
+
+static struct kmem_cache *meta_data_cache;      /* slab cache for meta data. */
+static DEFINE_MUTEX(meta_data_cache_lock);
+
+static u64 gk20a_bitmap_alloc_length(struct gk20a_allocator *a)
+{
+        struct gk20a_bitmap_allocator *ba = a->priv;
+
+        return ba->length;
+}
+
+static u64 gk20a_bitmap_alloc_base(struct gk20a_allocator *a)
+{
+        struct gk20a_bitmap_allocator *ba = a->priv;
+
+        return ba->base;
+}
+
+static int gk20a_bitmap_alloc_inited(struct gk20a_allocator *a)
+{
+        struct gk20a_bitmap_allocator *ba = a->priv;
+
+        return ba->inited;
+}
+
+static u64 gk20a_bitmap_alloc_end(struct gk20a_allocator *a)
+{
+        struct gk20a_bitmap_allocator *ba = a->priv;
+
+        return ba->base + ba->length;
+}
+
+static u64 gk20a_bitmap_alloc_fixed(struct gk20a_allocator *__a,
+                                    u64 base, u64 len)
+{
+        struct gk20a_bitmap_allocator *a = bitmap_allocator(__a);
+        u64 blks, offs, ret;
+
+        /* Compute the bit offset and make sure it's aligned to a block.  */
+        offs = base >> a->blk_shift;
+        if (offs * a->blk_size != base)
+                return 0;
+
+        offs -= a->bit_offs;
+
+        blks = len >> a->blk_shift;
+        if (blks * a->blk_size != len)
+                blks++;
+
+        alloc_lock(__a);
+
+        /* Check if the space requested is already occupied. */
+        ret = bitmap_find_next_zero_area(a->bitmap, a->num_bits, offs, blks, 0);
+        if (ret != offs)
+                goto fail;
+
+        bitmap_set(a->bitmap, offs, blks);
+
+        a->bytes_alloced += blks * a->blk_size;
+        a->nr_fixed_allocs++;
+        alloc_unlock(__a);
+
+        alloc_dbg(__a, "Alloc-fixed 0x%-10llx 0x%-5llx [bits=0x%llx (%llu)]\n",
+                  base, len, blks, blks);
+        return base;
+
+fail:
+        alloc_unlock(__a);
+        alloc_dbg(__a, "Alloc-fixed failed! (0x%llx)\n", base);
+        return 0;
+}
+
+/*
+ * Two possibilities for this function: either we are freeing a fixed allocation
+ * or we are freeing a regular alloc but with GPU_ALLOC_NO_ALLOC_PAGE defined.
+ *
+ * Note: this function won't do much error checking. Thus you could really
+ * confuse the allocator if you misuse this function.
+ */
+static void gk20a_bitmap_free_fixed(struct gk20a_allocator *__a,
+                                    u64 base, u64 len)
+{
+        struct gk20a_bitmap_allocator *a = bitmap_allocator(__a);
+        u64 blks, offs;
+
+        offs = base >> a->blk_shift;
+        if (WARN_ON(offs * a->blk_size != base))
+                return;
+
+        offs -= a->bit_offs;
+
+        blks = len >> a->blk_shift;
+        if (blks * a->blk_size != len)
+                blks++;
+
+        alloc_lock(__a);
+        bitmap_clear(a->bitmap, offs, blks);
+        a->bytes_freed += blks * a->blk_size;
+        alloc_unlock(__a);
+
+        alloc_dbg(__a, "Free-fixed 0x%-10llx 0x%-5llx [bits=0x%llx (%llu)]\n",
+                  base, len, blks, blks);
+}
+
+/*
+ * Add the passed alloc to the tree of stored allocations.
+ */
+static void insert_alloc_metadata(struct gk20a_bitmap_allocator *a,
+                                  struct gk20a_bitmap_alloc *alloc)
+{
+        struct rb_node **new = &a->allocs.rb_node;
+        struct rb_node *parent = NULL;
+        struct gk20a_bitmap_alloc *tmp;
+
+        while (*new) {
+                tmp = container_of(*new, struct gk20a_bitmap_alloc,
+                                   alloc_entry);
+
+                parent = *new;
+                if (alloc->base < tmp->base)
+                        new = &((*new)->rb_left);
+                else if (alloc->base > tmp->base)
+                        new = &((*new)->rb_right);
+                else {
+                        WARN_ON("Duplicate entries in RB alloc tree!\n");
+                        return;
+                }
+        }
+
+        rb_link_node(&alloc->alloc_entry, parent, new);
+        rb_insert_color(&alloc->alloc_entry, &a->allocs);
+}
+
+/*
+ * Find and remove meta-data from the outstanding allocations.
+ */
+static struct gk20a_bitmap_alloc *find_alloc_metadata(
+        struct gk20a_bitmap_allocator *a, u64 addr)
+{
+        struct rb_node *node = a->allocs.rb_node;
+        struct gk20a_bitmap_alloc *alloc;
+
+        while (node) {
+                alloc = container_of(node, struct gk20a_bitmap_alloc,
+                                     alloc_entry);
+
+                if (addr < alloc->base)
+                        node = node->rb_left;
+                else if (addr > alloc->base)
+                        node = node->rb_right;
+                else
+                        break;
+        }
+
+        if (!node)
+                return NULL;
+
+        rb_erase(node, &a->allocs);
+
+        return alloc;
+}
+
+/*
+ * Tree of alloc meta data stores the address of the alloc not the bit offset.
+ */
+static int __gk20a_bitmap_store_alloc(struct gk20a_bitmap_allocator *a,
+                                      u64 addr, u64 len)
+{
+        struct gk20a_bitmap_alloc *alloc =
+                kmem_cache_alloc(meta_data_cache, GFP_KERNEL);
+
+        if (!alloc)
+                return -ENOMEM;
+
+        alloc->base = addr;
+        alloc->length = len;
+
+        insert_alloc_metadata(a, alloc);
+
+        return 0;
+}
+
+/*
+ * @len is in bytes. This routine will figure out the right number of bits to
+ * actually allocate. The return is the address in bytes as well.
+ */
+static u64 gk20a_bitmap_alloc(struct gk20a_allocator *__a, u64 len)
+{
+        u64 blks, addr;
+        unsigned long offs, adjusted_offs;
+        struct gk20a_bitmap_allocator *a = bitmap_allocator(__a);
+
+        blks = len >> a->blk_shift;
+
+        if (blks * a->blk_size != len)
+                blks++;
+
+        alloc_lock(__a);
+
+        offs = bitmap_find_next_zero_area(a->bitmap, a->num_bits, 0, blks, 0);
+        if (offs >= a->num_bits)
+                goto fail;
+
+        bitmap_set(a->bitmap, offs, blks);
+
+        adjusted_offs = offs + a->bit_offs;
+        addr = ((u64)adjusted_offs) * a->blk_size;
+
+        /*
+         * Only do meta-data storage if we are allowed to allocate storage for
+         * that meta-data. The issue with using kmalloc() and friends is that
+         * in latency and success critical paths an alloc_page() call can either
+         * sleep for potentially a long time or, assuming GFP_ATOMIC, fail.
+         * Since we might not want either of these possibilities assume that the
+         * caller will keep what data it needs around to successfully free this
+         * allocation.
+         */
+        if (!(a->flags & GPU_ALLOC_NO_ALLOC_PAGE) &&
+            __gk20a_bitmap_store_alloc(a, addr, blks * a->blk_size))
+                goto fail_reset_bitmap;
+
+        alloc_dbg(__a, "Alloc 0x%-10llx 0x%-5llx [bits=0x%llx (%llu)]\n",
+                  addr, len, blks, blks);
+
+        a->nr_allocs++;
+        a->bytes_alloced += (blks * a->blk_size);
+        alloc_unlock(__a);
+
+        return addr;
+
+fail_reset_bitmap:
+        bitmap_clear(a->bitmap, offs, blks);
+fail:
+        alloc_unlock(__a);
+        alloc_dbg(__a, "Alloc failed!\n");
+        return 0;
+}
+
+static void gk20a_bitmap_free(struct gk20a_allocator *__a, u64 addr)
+{
+        struct gk20a_bitmap_allocator *a = bitmap_allocator(__a);
+        struct gk20a_bitmap_alloc *alloc = NULL;
+        u64 offs, adjusted_offs, blks;
+
+        alloc_lock(__a);
+
+        if (a->flags & GPU_ALLOC_NO_ALLOC_PAGE) {
+                WARN(1, "Using wrong free for NO_ALLOC_PAGE bitmap allocator");
+                goto done;
+        }
+
+        alloc = find_alloc_metadata(a, addr);
+        if (!alloc)
+                goto done;
+
+        /*
+         * Address comes from adjusted offset (i.e the bit offset with
+         * a->bit_offs added. So start with that and then work out the real
+         * offs into the bitmap.
+         */
+        adjusted_offs = addr >> a->blk_shift;
+        offs = adjusted_offs - a->bit_offs;
+        blks = alloc->length >> a->blk_shift;
+
+        bitmap_clear(a->bitmap, offs, blks);
+        alloc_dbg(__a, "Free  0x%-10llx \n", addr);
+
+        a->bytes_freed += alloc->length;
+
+done:
+        kfree(alloc);
+        alloc_unlock(__a);
+}
+
+static void gk20a_bitmap_alloc_destroy(struct gk20a_allocator *__a)
+{
+        struct gk20a_bitmap_allocator *a = bitmap_allocator(__a);
+        struct gk20a_bitmap_alloc *alloc;
+        struct rb_node *node;
+
+        /*
+         * Kill any outstanding allocations.
+         */
+        while ((node = rb_first(&a->allocs)) != NULL) {
+                alloc = container_of(node, struct gk20a_bitmap_alloc,
+                                     alloc_entry);
+
+                rb_erase(node, &a->allocs);
+                kfree(alloc);
+        }
+
+        kfree(a->bitmap);
+        kfree(a);
+}
+
+static void gk20a_bitmap_print_stats(struct gk20a_allocator *__a,
+                                     struct seq_file *s, int lock)
+{
+        struct gk20a_bitmap_allocator *a = bitmap_allocator(__a);
+
+        __alloc_pstat(s, __a, "Bitmap allocator params:\n");
+        __alloc_pstat(s, __a, "  start = 0x%llx\n", a->base);
+        __alloc_pstat(s, __a, "  end   = 0x%llx\n", a->base + a->length);
+        __alloc_pstat(s, __a, "  blks  = 0x%llx\n", a->num_bits);
+
+        /* Actual stats. */
+        __alloc_pstat(s, __a, "Stats:\n");
+        __alloc_pstat(s, __a, "  Number allocs = 0x%llx\n", a->nr_allocs);
+        __alloc_pstat(s, __a, "  Number fixed  = 0x%llx\n", a->nr_fixed_allocs);
+        __alloc_pstat(s, __a, "  Bytes alloced = 0x%llx\n", a->bytes_alloced);
+        __alloc_pstat(s, __a, "  Bytes freed   = 0x%llx\n", a->bytes_freed);
+        __alloc_pstat(s, __a, "  Outstanding   = 0x%llx\n",
+                      a->bytes_alloced - a->bytes_freed);
+}
+
+static const struct gk20a_allocator_ops bitmap_ops = {
+        .alloc          = gk20a_bitmap_alloc,
+        .free           = gk20a_bitmap_free,
+
+        .alloc_fixed    = gk20a_bitmap_alloc_fixed,
+        .free_fixed     = gk20a_bitmap_free_fixed,
+
+        .base           = gk20a_bitmap_alloc_base,
+        .length         = gk20a_bitmap_alloc_length,
+        .end            = gk20a_bitmap_alloc_end,
+        .inited         = gk20a_bitmap_alloc_inited,
+
+        .fini           = gk20a_bitmap_alloc_destroy,
+
+        .print_stats    = gk20a_bitmap_print_stats,
+};
+
+
+int gk20a_bitmap_allocator_init(struct gk20a_allocator *__a,
+                                const char *name, u64 base, u64 length,
+                                u64 blk_size, u64 flags)
+{
+        int err;
+        struct gk20a_bitmap_allocator *a;
+
+        mutex_lock(&meta_data_cache_lock);
+        if (!meta_data_cache)
+                meta_data_cache = KMEM_CACHE(gk20a_bitmap_alloc, 0);
+        mutex_unlock(&meta_data_cache_lock);
+
+        if (!meta_data_cache)
+                return -ENOMEM;
+
+        if (WARN_ON(blk_size & (blk_size - 1)))
+                return -EINVAL;
+
+        /*
+         * blk_size must be a power-of-2; base length also need to be aligned
+         * to blk_size.
+         */
+        if (blk_size & (blk_size - 1) ||
+            base & (blk_size - 1) || length & (blk_size - 1))
+                return -EINVAL;
+
+        if (base == 0) {
+                base = blk_size;
+                length -= blk_size;
+        }
+
+        a = kzalloc(sizeof(struct gk20a_bitmap_allocator), GFP_KERNEL);
+        if (!a)
+                return -ENOMEM;
+
+        err = __gk20a_alloc_common_init(__a, name, a, false, &bitmap_ops);
+        if (err)
+                goto fail;
+
+        a->base = base;
+        a->length = length;
+        a->blk_size = blk_size;
+        a->blk_shift = __ffs(a->blk_size);
+        a->num_bits = length >> a->blk_shift;
+        a->bit_offs = a->base >> a->blk_shift;
+        a->flags = flags;
+
+        a->bitmap = kzalloc(sizeof(*a->bitmap) * BITS_TO_LONGS(a->num_bits),
+                            GFP_KERNEL);
+        if (!a->bitmap)
+                goto fail;
+
+        a->inited = true;
+
+        gk20a_init_alloc_debug(__a);
+        alloc_dbg(__a, "New allocator: type      bitmap\n");
+        alloc_dbg(__a, "               base      0x%llx\n", a->base);
+        alloc_dbg(__a, "               bit_offs  0x%llx\n", a->bit_offs);
+        alloc_dbg(__a, "               size      0x%llx\n", a->length);
+        alloc_dbg(__a, "               blk_size  0x%llx\n", a->blk_size);
+        alloc_dbg(__a, "               flags     0x%llx\n", a->flags);
+
+        return 0;
+
+fail:
+        kfree(a);
+        return err;
+}