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Message-Id: <892fabb55ebe7bb35aa3f0be03ee3f93132b7acc.1527745258.git.baolin.wang@linaro.org>
Date: Thu, 31 May 2018 13:55:33 +0800
From: Baolin Wang <baolin.wang@...aro.org>
To: hch@....de, m.szyprowski@...sung.com
Cc: robin.murphy@....com, gregkh@...uxfoundation.org,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
arnd@...db.de, broonie@...nel.org, baolin.wang@...aro.org
Subject: [PATCH 2/2] dma-coherent: Change the bitmap APIs
The device coherent memory uses the bitmap helper functions, which take an
order of PAGE_SIZE, that means the pages size is always a power of 2 as the
allocation region. For Example, allocating 33 MB from a 33 MB dma_mem region
requires 64MB free memory in that region.
Thus we can change to use bitmap_find_next_zero_area()/bitmap_set()/
bitmap_clear() to present the allocation coherent memory, and reduce the
allocation granularity to be one PAGE_SIZE.
Moreover from Arnd's description:
"I believe that bitmap_allocate_region() was chosen here because it is
more efficient than bitmap_find_next_zero_area(), at least that is the
explanation given in https://en.wikipedia.org/wiki/Buddy_memory_allocation.
It's quite possible that we don't actually care about efficiency of
dma_alloc_*() since a) it's supposed to be called very rarely, and
b) the overhead of accessing uncached memory is likely higher than the
search through a relatively small bitmap".
Thus I think we can convert to change the allocation granularity to be
one PAGE_SIZE replacing with new bitmap APIs, which will not cause
efficiency issue.
Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
---
drivers/base/dma-coherent.c | 54 +++++++++++++++++++++++--------------------
include/linux/dma-mapping.h | 6 ++---
2 files changed, 32 insertions(+), 28 deletions(-)
diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index ce19832..4131540 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -143,34 +143,31 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
dma_addr_t device_addr, size_t size)
{
struct dma_coherent_mem *mem = dev->dma_mem;
- int order = get_order(size);
unsigned long flags;
- int pos, err;
-
- size += device_addr & ~PAGE_MASK;
+ int start_bit, nbits;
if (!mem)
return ERR_PTR(-EINVAL);
+ size += device_addr & ~PAGE_MASK;
+ nbits = (size + (1UL << PAGE_SHIFT) - 1) >> PAGE_SHIFT;
+
spin_lock_irqsave(&mem->spinlock, flags);
- pos = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
- err = bitmap_allocate_region(mem->bitmap, pos, order);
- if (!err)
- mem->avail -= 1 << order;
+ start_bit = PFN_DOWN(device_addr - dma_get_device_base(dev, mem));
+ bitmap_set(mem->bitmap, start_bit, nbits);
+ mem->avail -= nbits;
spin_unlock_irqrestore(&mem->spinlock, flags);
- if (err != 0)
- return ERR_PTR(err);
- return mem->virt_base + (pos << PAGE_SHIFT);
+ return mem->virt_base + (start_bit << PAGE_SHIFT);
}
EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
static void *__dma_alloc_from_coherent(struct dma_coherent_mem *mem,
ssize_t size, dma_addr_t *dma_handle)
{
- int order = get_order(size);
+ int nbits = (size + (1UL << PAGE_SHIFT) - 1) >> PAGE_SHIFT;
unsigned long flags;
- int pageno;
+ int start_bit, end_bit;
void *ret;
spin_lock_irqsave(&mem->spinlock, flags);
@@ -178,16 +175,22 @@ static void *__dma_alloc_from_coherent(struct dma_coherent_mem *mem,
if (unlikely(size > (mem->avail << PAGE_SHIFT)))
goto err;
- pageno = bitmap_find_free_region(mem->bitmap, mem->size, order);
- if (unlikely(pageno < 0))
+ start_bit = 0;
+ end_bit = mem->size;
+
+ start_bit = bitmap_find_next_zero_area(mem->bitmap, end_bit, start_bit,
+ nbits, 0);
+ if (start_bit >= end_bit)
goto err;
+ bitmap_set(mem->bitmap, start_bit, nbits);
+
/*
* Memory was found in the coherent area.
*/
- *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
- ret = mem->virt_base + (pageno << PAGE_SHIFT);
- mem->avail -= 1 << order;
+ *dma_handle = mem->device_base + (start_bit << PAGE_SHIFT);
+ ret = mem->virt_base + (start_bit << PAGE_SHIFT);
+ mem->avail -= nbits;
spin_unlock_irqrestore(&mem->spinlock, flags);
memset(ret, 0, size);
return ret;
@@ -241,16 +244,17 @@ void *dma_alloc_from_global_coherent(ssize_t size, dma_addr_t *dma_handle)
}
static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
- int order, void *vaddr)
+ int size, void *vaddr)
{
if (mem && vaddr >= mem->virt_base && vaddr <
(mem->virt_base + (mem->size << PAGE_SHIFT))) {
- int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
+ int nbits = (size + (1UL << PAGE_SHIFT) - 1) >> PAGE_SHIFT;
+ int start_bit = (vaddr - mem->virt_base) >> PAGE_SHIFT;
unsigned long flags;
spin_lock_irqsave(&mem->spinlock, flags);
- bitmap_release_region(mem->bitmap, page, order);
- mem->avail += 1 << order;
+ bitmap_clear(mem->bitmap, start_bit, nbits);
+ mem->avail += nbits;
spin_unlock_irqrestore(&mem->spinlock, flags);
return 1;
}
@@ -260,7 +264,7 @@ static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
/**
* dma_release_from_dev_coherent() - free memory to device coherent memory pool
* @dev: device from which the memory was allocated
- * @order: the order of pages allocated
+ * @size: size of release memory area
* @vaddr: virtual address of allocated pages
*
* This checks whether the memory was allocated from the per-device
@@ -269,11 +273,11 @@ static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
* Returns 1 if we correctly released the memory, or 0 if the caller should
* proceed with releasing memory from generic pools.
*/
-int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr)
+int dma_release_from_dev_coherent(struct device *dev, int size, void *vaddr)
{
struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
- return __dma_release_from_coherent(mem, order, vaddr);
+ return __dma_release_from_coherent(mem, size, vaddr);
}
EXPORT_SYMBOL(dma_release_from_dev_coherent);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f8ab1c0..29ae92e 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -162,7 +162,7 @@ static inline int is_device_dma_capable(struct device *dev)
*/
int dma_alloc_from_dev_coherent(struct device *dev, ssize_t size,
dma_addr_t *dma_handle, void **ret);
-int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr);
+int dma_release_from_dev_coherent(struct device *dev, int size, void *vaddr);
int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, size_t size, int *ret);
@@ -174,7 +174,7 @@ int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *cpu_addr,
#else
#define dma_alloc_from_dev_coherent(dev, size, handle, ret) (0)
-#define dma_release_from_dev_coherent(dev, order, vaddr) (0)
+#define dma_release_from_dev_coherent(dev, size, vaddr) (0)
#define dma_mmap_from_dev_coherent(dev, vma, vaddr, order, ret) (0)
static inline void *dma_alloc_from_global_coherent(ssize_t size,
@@ -540,7 +540,7 @@ static inline void dma_free_attrs(struct device *dev, size_t size,
BUG_ON(!ops);
WARN_ON(irqs_disabled());
- if (dma_release_from_dev_coherent(dev, get_order(size), cpu_addr))
+ if (dma_release_from_dev_coherent(dev, size, cpu_addr))
return;
if (!ops->free || !cpu_addr)
--
1.7.9.5
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