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Create an architecture-agnostic buffer pool manager that uses uma(9) to

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manage a set of power-of-2 sized buffers for bus_dmamem_alloc().

This allows the caller to provide the back-end allocator uma allocator,
allowing full control of the memory pages backing the pool.  For
convenience, it provides an optional builtin allocator that provides pages
allocated with the VM_MEMATTR_UNCACHEABLE attribute, for managing pools of
DMA buffers for BUS_DMA_COHERENT or BUS_DMA_NOCACHE.

This also allows the caller to specify a minimum alignment, and it ensures
that all buffers start on a boundary and have a length that's a multiple of
that value, to avoid using buffers that trigger partial cache line flushes.

Submitted by:	Ian Lepore <freebsd@damnhippie.dyndns.org>
This commit is contained in:
Olivier Houchard 2012-12-20 00:34:54 +00:00
parent 3254bef2ec
commit 05d9035003
2 changed files with 292 additions and 0 deletions
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174
sys/kern/subr_busdma_bufalloc.c Normal file
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/*-
* Copyright (c) 2012 Ian Lepore
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* Buffer allocation support routines for bus_dmamem_alloc implementations.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/busdma_bufalloc.h>
#include <sys/malloc.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/uma.h>
/*
* We manage buffer zones up to a page in size. Buffers larger than a page can
* be managed by one of the kernel's page-oriented memory allocation routines as
* efficiently as what we can do here. Also, a page is the largest size for
* which we can g'tee contiguity when using uma, and contiguity is one of the
* requirements we have to fulfill.
*/
#define MIN_ZONE_BUFSIZE 32
#define MAX_ZONE_BUFSIZE PAGE_SIZE
/*
* The static array of 12 bufzones is big enough to handle all the zones for the
* smallest supported allocation size of 32 through the largest supported page
* size of 64K. If you up the biggest page size number, up the array size too.
* Basically the size of the array needs to be log2(maxsize)-log2(minsize)+1,
* but I don't know of an easy way to express that as a compile-time constant.
*/
#if PAGE_SIZE > 65536
#error Unsupported page size
#endif
struct busdma_bufalloc {
bus_size_t min_size;
size_t num_zones;
struct busdma_bufzone buf_zones[12];
};
busdma_bufalloc_t
busdma_bufalloc_create(const char *name, bus_size_t minimum_alignment,
uma_alloc alloc_func, uma_free free_func, u_int32_t zcreate_flags)
{
struct busdma_bufalloc *ba;
struct busdma_bufzone *bz;
int i;
bus_size_t cursize;
ba = malloc(sizeof(struct busdma_bufalloc), M_DEVBUF,
M_ZERO | M_WAITOK);
ba->min_size = MAX(MIN_ZONE_BUFSIZE, minimum_alignment);
/*
* Each uma zone is created with an alignment of size-1, meaning that
* the alignment is equal to the size (I.E., 64 byte buffers are aligned
* to 64 byte boundaries, etc). This allows for a fast efficient test
* when deciding whether a pool buffer meets the constraints of a given
* tag used for allocation: the buffer is usable if tag->alignment <=
* bufzone->size.
*/
for (i = 0, bz = ba->buf_zones, cursize = ba->min_size;
i < nitems(ba->buf_zones) && cursize <= MAX_ZONE_BUFSIZE;
++i, ++bz, cursize <<= 1) {
snprintf(bz->name, sizeof(bz->name), "dma %.10s %lu",
name, cursize);
bz->size = cursize;
bz->umazone = uma_zcreate(bz->name, bz->size,
NULL, NULL, NULL, NULL, bz->size - 1, zcreate_flags);
if (bz->umazone == NULL) {
busdma_bufalloc_destroy(ba);
return (NULL);
}
if (alloc_func != NULL)
uma_zone_set_allocf(bz->umazone, alloc_func);
if (free_func != NULL)
uma_zone_set_freef(bz->umazone, free_func);
++ba->num_zones;
}
return (ba);
}
void
busdma_bufalloc_destroy(busdma_bufalloc_t ba)
{
struct busdma_bufzone *bz;
int i;
if (ba == NULL)
return;
for (i = 0, bz = ba->buf_zones; i < ba->num_zones; ++i, ++bz) {
uma_zdestroy(bz->umazone);
}
free(ba, M_DEVBUF);
}
struct busdma_bufzone *
busdma_bufalloc_findzone(busdma_bufalloc_t ba, bus_size_t size)
{
struct busdma_bufzone *bz;
int i;
if (size > MAX_ZONE_BUFSIZE)
return (NULL);
for (i = 0, bz = ba->buf_zones; i < ba->num_zones; ++i, ++bz) {
if (bz->size >= size)
return (bz);
}
panic("Didn't find a buffer zone of the right size");
}
void *
busdma_bufalloc_alloc_uncacheable(uma_zone_t zone, int size, u_int8_t *pflag,
int wait)
{
#ifdef VM_MEMATTR_UNCACHEABLE
/* Inform UMA that this allocator uses kernel_map/object. */
*pflag = UMA_SLAB_KERNEL;
return ((void *)kmem_alloc_attr(kernel_map, size, wait, 0,
BUS_SPACE_MAXADDR, VM_MEMATTR_UNCACHEABLE));
#else
panic("VM_MEMATTR_UNCACHEABLE unavailable");
#endif /* VM_MEMATTR_UNCACHEABLE */
}
void
busdma_bufalloc_free_uncacheable(void *item, int size, u_int8_t pflag)
{
kmem_free(kernel_map, (vm_offset_t)item, size);
}

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sys/sys/busdma_bufalloc.h Normal file
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/*-
* Copyright (c) 2012 Ian Lepore
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* $FreeBSD$
*/
/*
* A buffer pool manager, for use by a platform's busdma implementation.
*/
#ifndef _MACHINE_BUSDMA_BUFALLOC_H_
#define _MACHINE_BUSDMA_BUFALLOC_H_
#include <machine/bus.h>
#include <vm/uma.h>
/*
* Information about a buffer zone, returned by busdma_bufalloc_findzone().
*/
struct busdma_bufzone {
bus_size_t size;
uma_zone_t umazone;
char name[24];
};
/*
* Opaque handle type returned by busdma_bufalloc_create().
*/
struct busdma_bufalloc;
typedef struct busdma_bufalloc *busdma_bufalloc_t;
/*
* Create an allocator that manages a pool of DMA buffers.
*
* The allocator manages a collection of uma(9) zones of buffers in power-of-two
* sized increments ranging from minimum_alignment to the platform's PAGE_SIZE.
* The buffers within each zone are aligned on boundaries corresponding to the
* buffer size, and thus by implication each buffer is contiguous within a page
* and does not cross a power of two boundary larger than the buffer size.
* These rules are intended to make it easy for a busdma implementation to
* check whether a tag's constraints allow use of a buffer from the allocator.
*
* minimum_alignment is also the minimum buffer allocation size. For platforms
* with software-assisted cache coherency, this is typically the data cache line
* size (and MUST not be smaller than the cache line size).
*
* name appears in zone stats as 'dma name nnnnn' where 'dma' is fixed and
* 'nnnnn' is the size of buffers in that zone.
*
* If if the alloc/free function pointers are NULL, the regular uma internal
* allocators are used (I.E., you get "plain old kernel memory"). On a platform
* with an exclusion zone that applies to all DMA operations, a custom allocator
* could be used to ensure no buffer memory is ever allocated from that zone,
* allowing the bus_dmamem_alloc() implementation to make the assumption that
* buffers provided by the allocation could never lead to the need for a bounce.
*/
busdma_bufalloc_t busdma_bufalloc_create(const char *name,
bus_size_t minimum_alignment,
uma_alloc uma_alloc_func, uma_free uma_free_func,
u_int32_t uma_zcreate_flags);
/*
* Destroy an allocator created by busdma_bufalloc_create().
* Safe to call with a NULL pointer.
*/
void busdma_bufalloc_destroy(busdma_bufalloc_t ba);
/*
* Return a pointer to the busdma_bufzone that should be used to allocate or
* free a buffer of the given size. Returns NULL if the size is larger than the
* largest zone handled by the allocator.
*/
struct busdma_bufzone * busdma_bufalloc_findzone(busdma_bufalloc_t ba,
bus_size_t size);
/*
* These built-in allocation routines are available for managing a pools of
* uncacheable memory on platforms that support VM_MEMATTR_UNCACHEABLE.
*
* Allocation is done using kmem_alloc_attr() with these parameters:
* lowaddr = 0
* highaddr = BUS_SPACE_MAXADDR
* memattr = VM_MEMATTR_UNCACHEABLE.
*
* If your platform has no exclusion region (lowaddr/highaddr), and its pmap
* routines support pmap_page_set_memattr() and the VM_MEMATTR_UNCACHEABLE flag
* you can probably use these when you need uncacheable buffers.
*/
void * busdma_bufalloc_alloc_uncacheable(uma_zone_t zone, int size,
u_int8_t *pflag, int wait);
void busdma_bufalloc_free_uncacheable(void *item, int size, u_int8_t pflag);
#endif /* _MACHINE_BUSDMA_BUFALLOC_H_ */