dma_map_sg - notro/udrm-kernel GitHub Wiki
#define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, 0)
/*
* dma_maps_sg_attrs returns 0 on error and > 0 on success.
* It should never return a value < 0.
*/
static inline int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir,
unsigned long attrs)
{
struct dma_map_ops *ops = get_dma_ops(dev);
int i, ents;
struct scatterlist *s;
for_each_sg(sg, s, nents, i)
kmemcheck_mark_initialized(sg_virt(s), s->length);
BUG_ON(!valid_dma_direction(dir));
ents = ops->map_sg(dev, sg, nents, dir, attrs);
BUG_ON(ents < 0);
debug_dma_map_sg(dev, sg, nents, ents, dir);
return ents;
}struct dma_map_ops arm_dma_ops = {
.map_sg = arm_dma_map_sg,
.map_page = arm_dma_map_page,
};
/**
* arm_dma_map_sg - map a set of SG buffers for streaming mode DMA
* @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
* @sg: list of buffers
* @nents: number of buffers to map
* @dir: DMA transfer direction
*
* Map a set of buffers described by scatterlist in streaming mode for DMA.
* This is the scatter-gather version of the dma_map_single interface.
* Here the scatter gather list elements are each tagged with the
* appropriate dma address and length. They are obtained via
* sg_dma_{address,length}.
*
* Device ownership issues as mentioned for dma_map_single are the same
* here.
*/
int arm_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction dir, unsigned long attrs)
{
struct dma_map_ops *ops = get_dma_ops(dev);
struct scatterlist *s;
int i, j;
for_each_sg(sg, s, nents, i) {
#ifdef CONFIG_NEED_SG_DMA_LENGTH
s->dma_length = s->length;
#endif
s->dma_address = ops->map_page(dev, sg_page(s), s->offset,
s->length, dir, attrs);
if (dma_mapping_error(dev, s->dma_address))
goto bad_mapping;
}
return nents;
bad_mapping:
for_each_sg(sg, s, i, j)
ops->unmap_page(dev, sg_dma_address(s), sg_dma_len(s), dir, attrs);
return 0;
}
/**
* arm_dma_map_page - map a portion of a page for streaming DMA
* @dev: valid struct device pointer, or NULL for ISA and EISA-like devices
* @page: page that buffer resides in
* @offset: offset into page for start of buffer
* @size: size of buffer to map
* @dir: DMA transfer direction
*
* Ensure that any data held in the cache is appropriately discarded
* or written back.
*
* The device owns this memory once this call has completed. The CPU
* can regain ownership by calling dma_unmap_page().
*/
static dma_addr_t arm_dma_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
if ((attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
__dma_page_cpu_to_dev(page, offset, size, dir);
return pfn_to_dma(dev, page_to_pfn(page)) + offset;
}
/*
* Make an area consistent for devices.
* Note: Drivers should NOT use this function directly, as it will break
* platforms with CONFIG_DMABOUNCE.
* Use the driver DMA support - see dma-mapping.h (dma_sync_*)
*/
static void __dma_page_cpu_to_dev(struct page *page, unsigned long off,
size_t size, enum dma_data_direction dir)
{
phys_addr_t paddr;
dma_cache_maint_page(page, off, size, dir, dmac_map_area);
paddr = page_to_phys(page) + off;
if (dir == DMA_FROM_DEVICE) {
outer_inv_range(paddr, paddr + size);
} else {
outer_clean_range(paddr, paddr + size);
}
/* FIXME: non-speculating: flush on bidirectional mappings? */
}
static void dma_cache_maint_page(struct page *page, unsigned long offset,
size_t size, enum dma_data_direction dir,
void (*op)(const void *, size_t, int))
{
unsigned long pfn;
size_t left = size;
pfn = page_to_pfn(page) + offset / PAGE_SIZE;
offset %= PAGE_SIZE;
/*
* A single sg entry may refer to multiple physically contiguous
* pages. But we still need to process highmem pages individually.
* If highmem is not configured then the bulk of this loop gets
* optimized out.
*/
do {
size_t len = left;
void *vaddr;
page = pfn_to_page(pfn);
if (PageHighMem(page)) {
<snip>
} else {
vaddr = page_address(page) + offset;
op(vaddr, len, dir);
}
offset = 0;
pfn++;
left -= len;
} while (left);
}outer_inv_range() and outer_clean_range() are empty on Raspberry Pi.
Raspberry Pi 1: CONFIG_CPU_V6
Raspberry Pi 2/3: CONFIG_CPU_V7
/*
* Cache Model
* ===========
*/
#undef _CACHE
#undef MULTI_CACHE
#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_V6K)
# ifdef _CACHE
# define MULTI_CACHE 1
# else
# define _CACHE v6
# endif
#endif
#if defined(CONFIG_CPU_V7)
# ifdef _CACHE
# define MULTI_CACHE 1
# else
# define _CACHE v7
# endif
#endif#ifndef MULTI_CACHE
#define dmac_map_area __glue(_CACHE,_dma_map_area)
/*
* dma_map_area(start, size, dir)
* - start - kernel virtual start address
* - size - size of region
* - dir - DMA direction
*/
ENTRY(v7_dma_map_area)
add r1, r1, r0
teq r2, #DMA_FROM_DEVICE
beq v7_dma_inv_range
b v7_dma_clean_range
ENDPROC(v7_dma_map_area)ARM assembler:
- Use the TEQ instruction to test if two values are equal, without affecting the V or C flags (as CMP does).
- beq: branch if equal
v7_dma_map_area:
If DMA_FROM_DEVICE
Invalidate data cache
Else
Clean data cache
/*
* v7_dma_inv_range(start,end)
*
* Invalidate the data cache within the specified region; we will
* be performing a DMA operation in this region and we want to
* purge old data in the cache.
*
* - start - virtual start address of region
* - end - virtual end address of region
*/
v7_dma_inv_range:
dcache_line_size r2, r3
sub r3, r2, #1
tst r0, r3
bic r0, r0, r3
mcrne p15, 0, r0, c7, c14, 1 @ clean & invalidate D / U line
tst r1, r3
bic r1, r1, r3
mcrne p15, 0, r1, c7, c14, 1 @ clean & invalidate D / U line
1:
mcr p15, 0, r0, c7, c6, 1 @ invalidate D / U line
add r0, r0, r2
cmp r0, r1
blo 1b
dsb st
ret lr
ENDPROC(v7_dma_inv_range)
/*
* v7_dma_clean_range(start,end)
* - start - virtual start address of region
* - end - virtual end address of region
*/
v7_dma_clean_range:
dcache_line_size r2, r3
sub r3, r2, #1
bic r0, r0, r3
1:
mcr p15, 0, r0, c7, c10, 1 @ clean D / U line
add r0, r0, r2
cmp r0, r1
blo 1b
dsb st
ret lr
ENDPROC(v7_dma_clean_range)