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swiotlb: add documentation and rename swiotlb_do_find_slots() 

Add some kernel-doc comments and move the existing documentation of struct
io_tlb_slot to its correct location. The latter was forgotten in commit
942a8186eb ("swiotlb: move struct io_tlb_slot to swiotlb.c").

Use the opportunity to give swiotlb_do_find_slots() a more descriptive name
and make it clear how it differs from swiotlb_find_slots().

Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Petr Tesarik 2023-08-01 08:23:58 +02:00 committed by Christoph Hellwig
parent 05ee774122
commit fea18777a7
2 changed files with 66 additions and 10 deletions
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15
include/linux/swiotlb.h
View File

@ -76,10 +76,6 @@ dma_addr_t swiotlb_map(struct device *dev, phys_addr_t phys,
* @nslabs: The number of IO TLB blocks (in groups of 64) between @start and
* @end. For default swiotlb, this is command line adjustable via
* setup_io_tlb_npages.
* @list: The free list describing the number of free entries available
* from each index.
* @orig_addr: The original address corresponding to a mapped entry.
* @alloc_size: Size of the allocated buffer.
* @debugfs: The dentry to debugfs.
* @late_alloc: %true if allocated using the page allocator
* @force_bounce: %true if swiotlb bouncing is forced
@ -111,6 +107,17 @@ struct io_tlb_mem {
#endif
};
/**
* is_swiotlb_buffer() - check if a physical address belongs to a swiotlb
* @dev: Device which has mapped the buffer.
* @paddr: Physical address within the DMA buffer.
*
* Check if @paddr points into a bounce buffer.
*
* Return:
* * %true if @paddr points into a bounce buffer
* * %false otherwise
*/
static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
{
struct io_tlb_mem *mem = dev->dma_io_tlb_mem;

61
kernel/dma/swiotlb.c
View File

@ -62,6 +62,13 @@
#define INVALID_PHYS_ADDR (~(phys_addr_t)0)
/**
* struct io_tlb_slot - IO TLB slot descriptor
* @orig_addr: The original address corresponding to a mapped entry.
* @alloc_size: Size of the allocated buffer.
* @list: The free list describing the number of free entries available
* from each index.
*/
struct io_tlb_slot {
phys_addr_t orig_addr;
size_t alloc_size;
@ -635,11 +642,22 @@ static void dec_used(struct io_tlb_mem *mem, unsigned int nslots)
}
#endif /* CONFIG_DEBUG_FS */
/*
* Find a suitable number of IO TLB entries size that will fit this request and
* allocate a buffer from that IO TLB pool.
/**
* swiotlb_area_find_slots() - search for slots in one IO TLB memory area
* @dev: Device which maps the buffer.
* @area_index: Index of the IO TLB memory area to be searched.
* @orig_addr: Original (non-bounced) IO buffer address.
* @alloc_size: Total requested size of the bounce buffer,
* including initial alignment padding.
* @alloc_align_mask: Required alignment of the allocated buffer.
*
* Find a suitable sequence of IO TLB entries for the request and allocate
* a buffer from the given IO TLB memory area.
* This function takes care of locking.
*
* Return: Index of the first allocated slot, or -1 on error.
*/
static int swiotlb_do_find_slots(struct device *dev, int area_index,
static int swiotlb_area_find_slots(struct device *dev, int area_index,
phys_addr_t orig_addr, size_t alloc_size,
unsigned int alloc_align_mask)
{
@ -734,6 +752,19 @@ found:
return slot_index;
}
/**
* swiotlb_find_slots() - search for slots in the whole swiotlb
* @dev: Device which maps the buffer.
* @orig_addr: Original (non-bounced) IO buffer address.
* @alloc_size: Total requested size of the bounce buffer,
* including initial alignment padding.
* @alloc_align_mask: Required alignment of the allocated buffer.
*
* Search through the whole software IO TLB to find a sequence of slots that
* match the allocation constraints.
*
* Return: Index of the first allocated slot, or -1 on error.
*/
static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
size_t alloc_size, unsigned int alloc_align_mask)
{
@ -742,8 +773,8 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
int i = start, index;
do {
index = swiotlb_do_find_slots(dev, i, orig_addr, alloc_size,
alloc_align_mask);
index = swiotlb_area_find_slots(dev, i, orig_addr, alloc_size,
alloc_align_mask);
if (index >= 0)
return index;
if (++i >= mem->nareas)
@ -755,6 +786,15 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
#ifdef CONFIG_DEBUG_FS
/**
* mem_used() - get number of used slots in an allocator
* @mem: Software IO TLB allocator.
*
* The result is accurate in this version of the function, because an atomic
* counter is available if CONFIG_DEBUG_FS is set.
*
* Return: Number of used slots.
*/
static unsigned long mem_used(struct io_tlb_mem *mem)
{
return atomic_long_read(&mem->total_used);
@ -762,6 +802,15 @@ static unsigned long mem_used(struct io_tlb_mem *mem)
#else /* !CONFIG_DEBUG_FS */
/**
* mem_used() - get number of used slots in an allocator
* @mem: Software IO TLB allocator.
*
* The result is not accurate, because there is no locking of individual
* areas.
*
* Return: Approximate number of used slots.
*/
static unsigned long mem_used(struct io_tlb_mem *mem)
{
int i;