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Subject[RFC PATCH 1/2] drivers: dma-coherent: Introduce interface for default DMA pool
Date
Christoph noticed [1] that default DMA pool in current form overload
the DMA coherent infrastructure. In reply, Robin suggested to split
the per-device vs. global pool interfaces, so allocation/release from
default DMA pool is driven by dma ops implementation.

This patch implements Robin's idea and provide interface to
allocate/release/mmap the default/global DMA pool.

[1] https://lkml.org/lkml/2017/7/7/370
[2] https://lkml.org/lkml/2017/7/7/431

Suggested-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
drivers/base/dma-coherent.c | 159 +++++++++++++++++++++++++++++---------------
include/linux/dma-mapping.h | 24 +++++++
2 files changed, 130 insertions(+), 53 deletions(-)

diff --git a/drivers/base/dma-coherent.c b/drivers/base/dma-coherent.c
index 2ae24c2..6ab9039 100644
--- a/drivers/base/dma-coherent.c
+++ b/drivers/base/dma-coherent.c
@@ -25,7 +25,7 @@ static inline struct dma_coherent_mem *dev_get_coherent_memory(struct device *de
{
if (dev && dev->dma_mem)
return dev->dma_mem;
- return dma_coherent_default_memory;
+ return NULL;
}

static inline dma_addr_t dma_get_device_base(struct device *dev,
@@ -165,34 +165,15 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
}
EXPORT_SYMBOL(dma_mark_declared_memory_occupied);

-/**
- * dma_alloc_from_coherent() - try to allocate memory from the per-device coherent area
- *
- * @dev: device from which we allocate memory
- * @size: size of requested memory area
- * @dma_handle: This will be filled with the correct dma handle
- * @ret: This pointer will be filled with the virtual address
- * to allocated area.
- *
- * This function should be only called from per-arch dma_alloc_coherent()
- * to support allocation from per-device coherent memory pools.
- *
- * Returns 0 if dma_alloc_coherent should continue with allocating from
- * generic memory areas, or !0 if dma_alloc_coherent should return @ret.
- */
-int dma_alloc_from_coherent(struct device *dev, ssize_t size,
- dma_addr_t *dma_handle, void **ret)
+static void *__dma_alloc_from_coherent(struct dma_coherent_mem *mem,
+ ssize_t size, dma_addr_t *dma_handle)
{
- struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
int order = get_order(size);
unsigned long flags;
int pageno;
int dma_memory_map;
+ void *ret;

- if (!mem)
- return 0;
-
- *ret = NULL;
spin_lock_irqsave(&mem->spinlock, flags);

if (unlikely(size > (mem->size << PAGE_SHIFT)))
@@ -203,21 +184,51 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
goto err;

/*
- * Memory was found in the per-device area.
+ * Memory was found in the coherent area.
*/
- *dma_handle = dma_get_device_base(dev, mem) + (pageno << PAGE_SHIFT);
- *ret = mem->virt_base + (pageno << PAGE_SHIFT);
+ *dma_handle = mem->device_base + (pageno << PAGE_SHIFT);
+ ret = mem->virt_base + (pageno << PAGE_SHIFT);
dma_memory_map = (mem->flags & DMA_MEMORY_MAP);
spin_unlock_irqrestore(&mem->spinlock, flags);
if (dma_memory_map)
- memset(*ret, 0, size);
+ memset(ret, 0, size);
else
- memset_io(*ret, 0, size);
+ memset_io(ret, 0, size);

- return 1;
+ return ret;

err:
spin_unlock_irqrestore(&mem->spinlock, flags);
+ return NULL;
+}
+
+/**
+ * dma_alloc_from_coherent() - try to allocate memory from the per-device coherent area
+ *
+ * @dev: device from which we allocate memory
+ * @size: size of requested memory area
+ * @dma_handle: This will be filled with the correct dma handle
+ * @ret: This pointer will be filled with the virtual address
+ * to allocated area.
+ *
+ * This function should be only called from per-arch dma_alloc_coherent()
+ * to support allocation from per-device coherent memory pools.
+ *
+ * Returns 0 if dma_alloc_coherent should continue with allocating from
+ * generic memory areas, or !0 if dma_alloc_coherent should return @ret.
+ */
+int dma_alloc_from_coherent(struct device *dev, ssize_t size,
+ dma_addr_t *dma_handle, void **ret)
+{
+ struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);
+
+ if (!mem)
+ return 0;
+
+ *ret = __dma_alloc_from_coherent(mem, size, dma_handle);
+ if (*ret)
+ return 1;
+
/*
* In the case where the allocation can not be satisfied from the
* per-device area, try to fall back to generic memory if the
@@ -227,6 +238,31 @@ int dma_alloc_from_coherent(struct device *dev, ssize_t size,
}
EXPORT_SYMBOL(dma_alloc_from_coherent);

+void *dma_alloc_from_global_coherent(ssize_t size, dma_addr_t *dma_handle)
+{
+ if (!dma_coherent_default_memory)
+ return NULL;
+
+ return __dma_alloc_from_coherent(dma_coherent_default_memory, size, dma_handle);
+}
+
+
+static int __dma_release_from_coherent(struct dma_coherent_mem *mem,
+ int order, void *vaddr)
+{
+ if (mem && vaddr >= mem->virt_base && vaddr <
+ (mem->virt_base + (mem->size << PAGE_SHIFT))) {
+ int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
+ unsigned long flags;
+
+ spin_lock_irqsave(&mem->spinlock, flags);
+ bitmap_release_region(mem->bitmap, page, order);
+ spin_unlock_irqrestore(&mem->spinlock, flags);
+ return 1;
+ }
+ return 0;
+}
+
/**
* dma_release_from_coherent() - try to free the memory allocated from per-device coherent memory pool
* @dev: device from which the memory was allocated
@@ -244,19 +280,42 @@ int dma_release_from_coherent(struct device *dev, int order, void *vaddr)
{
struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

- if (mem && vaddr >= mem->virt_base && vaddr <
+ return __dma_release_from_coherent(mem, order, vaddr);
+}
+EXPORT_SYMBOL(dma_release_from_coherent);
+
+
+int dma_release_from_global_coherent(int order, void *vaddr)
+{
+ if (!dma_coherent_default_memory)
+ return 0;
+
+ return __dma_release_from_coherent(dma_coherent_default_memory,
+ order, vaddr);
+}
+
+static int __dma_mmap_from_coherent(struct dma_coherent_mem *mem,
+ struct vm_area_struct *vma, void *vaddr,
+ size_t size, int *ret)
+{
+ if (mem && vaddr >= mem->virt_base && vaddr + size <=
(mem->virt_base + (mem->size << PAGE_SHIFT))) {
- int page = (vaddr - mem->virt_base) >> PAGE_SHIFT;
- unsigned long flags;
+ unsigned long off = vma->vm_pgoff;
+ int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
+ int user_count = vma_pages(vma);
+ int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

- spin_lock_irqsave(&mem->spinlock, flags);
- bitmap_release_region(mem->bitmap, page, order);
- spin_unlock_irqrestore(&mem->spinlock, flags);
+ *ret = -ENXIO;
+ if (off < count && user_count <= count - off) {
+ unsigned long pfn = mem->pfn_base + start + off;
+ *ret = remap_pfn_range(vma, vma->vm_start, pfn,
+ user_count << PAGE_SHIFT,
+ vma->vm_page_prot);
+ }
return 1;
}
return 0;
}
-EXPORT_SYMBOL(dma_release_from_coherent);

/**
* dma_mmap_from_coherent() - try to mmap the memory allocated from
@@ -278,26 +337,20 @@ int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
{
struct dma_coherent_mem *mem = dev_get_coherent_memory(dev);

- if (mem && vaddr >= mem->virt_base && vaddr + size <=
- (mem->virt_base + (mem->size << PAGE_SHIFT))) {
- unsigned long off = vma->vm_pgoff;
- int start = (vaddr - mem->virt_base) >> PAGE_SHIFT;
- int user_count = vma_pages(vma);
- int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-
- *ret = -ENXIO;
- if (off < count && user_count <= count - off) {
- unsigned long pfn = mem->pfn_base + start + off;
- *ret = remap_pfn_range(vma, vma->vm_start, pfn,
- user_count << PAGE_SHIFT,
- vma->vm_page_prot);
- }
- return 1;
- }
- return 0;
+ return __dma_mmap_from_coherent(mem, vma, vaddr, size, ret);
}
EXPORT_SYMBOL(dma_mmap_from_coherent);

+int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *vaddr,
+ size_t size, int *ret)
+{
+ if (!dma_coherent_default_memory)
+ return 0;
+
+ return __dma_mmap_from_coherent(dma_coherent_default_memory, vma,
+ vaddr, size, ret);
+}
+
/*
* Support for reserved memory regions defined in device tree
*/
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 843ab86..8f2289f 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -163,10 +163,34 @@ int dma_release_from_coherent(struct device *dev, int order, void *vaddr);

int dma_mmap_from_coherent(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, size_t size, int *ret);
+
+void *dma_alloc_from_global_coherent(ssize_t size, dma_addr_t *dma_handle);
+int dma_release_from_global_coherent(int order, void *vaddr);
+int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *cpu_addr,
+ size_t size, int *ret);
+
#else
#define dma_alloc_from_coherent(dev, size, handle, ret) (0)
#define dma_release_from_coherent(dev, order, vaddr) (0)
#define dma_mmap_from_coherent(dev, vma, vaddr, order, ret) (0)
+
+static inline void *dma_alloc_from_global_coherent(ssize_t size,
+ dma_addr_t *dma_handle)
+{
+ return NULL;
+}
+
+static inline int dma_release_from_global_coherent(int order, void *vaddr)
+{
+ return 0;
+}
+
+static inline int dma_mmap_from_global_coherent(struct vm_area_struct *vma,
+ void *cpu_addr, size_t size,
+ int *ret)
+{
+ return 0;
+}
#endif /* CONFIG_HAVE_GENERIC_DMA_COHERENT */

#ifdef CONFIG_HAS_DMA
--
2.0.0
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