Re: [Linaro-mm-sig] [PATCHv3 13/22] staging: android: ion: Use CMA APIs directly

On 04/10/2017 11:47 PM, Laurent Pinchart wrote:

Hi Laura,

Thank you for the patch.

On Monday 03 Apr 2017 11:57:55 Laura Abbott wrote:

...

When CMA was first introduced, its primary use was for DMA allocation and the only way to get CMA memory was to call dma_alloc_coherent. This put Ion in an awkward position since there was no device structure readily available and setting one up messed up the coherency model. These days, CMA can be allocated directly from the APIs. Switch to using this model to avoid needing a dummy device. This also mitigates some of the caching problems (e.g. dma_alloc_coherent only returning uncached memory).

Do we have a guarantee that the DMA mapping API, which we have to use for cache handling, will always support memory we allocate directly from CMA behind its back ?

CMA pages are no different than other pages allocated via the buddy allocator. There should be no issue passing that memory to the streaming API.

Thanks, Laura

...

Signed-off-by: Laura Abbott labbott@redhat.com

drivers/staging/android/ion/Kconfig | 7 +++ drivers/staging/android/ion/Makefile | 3 +- drivers/staging/android/ion/ion_cma_heap.c | 97 +++++++-------------------- 3 files changed, 35 insertions(+), 72 deletions(-)

diff --git a/drivers/staging/android/ion/Kconfig b/drivers/staging/android/ion/Kconfig index 206c4de..15108c4 100644 --- a/drivers/staging/android/ion/Kconfig +++ b/drivers/staging/android/ion/Kconfig @@ -10,3 +10,10 @@ menuconfig ION If you're not using Android its probably safe to say N here.

+config ION_CMA_HEAP

• bool "Ion CMA heap support"
• depends on ION && CMA
• help

•  Choose this option to enable CMA heaps with Ion. This heap is backed
  

•  by the Contiguous Memory Allocator (CMA). If your system has these
  

•  regions, you should say Y here.
  

diff --git a/drivers/staging/android/ion/Makefile b/drivers/staging/android/ion/Makefile index 26672a0..66d0c4a 100644 --- a/drivers/staging/android/ion/Makefile +++ b/drivers/staging/android/ion/Makefile @@ -1,6 +1,7 @@ obj-$(CONFIG_ION) += ion.o ion-ioctl.o ion_heap.o \ ion_page_pool.o ion_system_heap.o \

• 	ion_carveout_heap.o ion_chunk_heap.o ion_cma_heap.o
  

• 	ion_carveout_heap.o ion_chunk_heap.o
  

+obj-$(CONFIG_ION_CMA_HEAP) += ion_cma_heap.o ifdef CONFIG_COMPAT obj-$(CONFIG_ION) += compat_ion.o endif diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c index d562fd7..f3e0f59 100644 --- a/drivers/staging/android/ion/ion_cma_heap.c +++ b/drivers/staging/android/ion/ion_cma_heap.c @@ -19,24 +19,19 @@ #include <linux/slab.h> #include <linux/errno.h> #include <linux/err.h> -#include <linux/dma-mapping.h> +#include <linux/cma.h> +#include <linux/scatterlist.h>

#include "ion.h" #include "ion_priv.h"

struct ion_cma_heap { struct ion_heap heap;

• struct device *dev;

• struct cma *cma;

};

#define to_cma_heap(x) container_of(x, struct ion_cma_heap, heap)

-struct ion_cma_buffer_info {

• void *cpu_addr;
• dma_addr_t handle;
• struct sg_table *table;

-};

/* ION CMA heap operations functions */ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer, @@ -44,93 +39,53 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer, unsigned long flags) { struct ion_cma_heap *cma_heap = to_cma_heap(heap);

• struct device *dev = cma_heap->dev;
• struct ion_cma_buffer_info *info;
• dev_dbg(dev, "Request buffer allocation len %ld\n", len);
• if (buffer->flags & ION_FLAG_CACHED)

• return -EINVAL;
  

• struct sg_table *table;
• struct page *pages;
• int ret;

• info = kzalloc(sizeof(*info), GFP_KERNEL);
• if (!info)

• pages = cma_alloc(cma_heap->cma, len, 0, GFP_KERNEL);
• if (!pages) return -ENOMEM;

• info->cpu_addr = dma_alloc_coherent(dev, len, &(info->handle),

• 				GFP_HIGHUSER | __GFP_ZERO);
  

• if (!info->cpu_addr) {

• dev_err(dev, "Fail to allocate buffer\n");
  

• table = kmalloc(sizeof(struct sg_table), GFP_KERNEL);
• if (!table) goto err;

• }

• info->table = kmalloc(sizeof(*info->table), GFP_KERNEL);

• if (!info->table)

• ret = sg_alloc_table(table, 1, GFP_KERNEL);
• if (ret) goto free_mem;

• if (dma_get_sgtable(dev, info->table, info->cpu_addr, info->handle,

• 	    len))
  

• goto free_table;
  

• /* keep this for memory release */
• buffer->priv_virt = info;
• buffer->sg_table = info->table;
• dev_dbg(dev, "Allocate buffer %p\n", buffer);

• sg_set_page(table->sgl, pages, len, 0);
• buffer->priv_virt = pages;
• buffer->sg_table = table; return 0;

-free_table:

• kfree(info->table);

free_mem:

• dma_free_coherent(dev, len, info->cpu_addr, info->handle);

• kfree(table);

err:

• kfree(info);

• cma_release(cma_heap->cma, pages, buffer->size); return -ENOMEM;

}

static void ion_cma_free(struct ion_buffer *buffer) { struct ion_cma_heap *cma_heap = to_cma_heap(buffer->heap);

• struct device *dev = cma_heap->dev;
• struct ion_cma_buffer_info *info = buffer->priv_virt;

• struct page *pages = buffer->priv_virt;

• dev_dbg(dev, "Release buffer %p\n", buffer); /* release memory */
• dma_free_coherent(dev, buffer->size, info->cpu_addr, info->handle);

• cma_release(cma_heap->cma, pages, buffer->size); /* release sg table */

• sg_free_table(info->table);
• kfree(info->table);
• kfree(info);

-}

-static int ion_cma_mmap(struct ion_heap *mapper, struct ion_buffer *buffer,

• 	struct vm_area_struct *vma)
  

-{

• struct ion_cma_heap *cma_heap = to_cma_heap(buffer->heap);
• struct device *dev = cma_heap->dev;
• struct ion_cma_buffer_info *info = buffer->priv_virt;
• return dma_mmap_coherent(dev, vma, info->cpu_addr, info->handle,

• 		 buffer->size);
  

-}

-static void *ion_cma_map_kernel(struct ion_heap *heap,

• 		struct ion_buffer *buffer)
  

-{

• struct ion_cma_buffer_info *info = buffer->priv_virt;
• /* kernel memory mapping has been done at allocation time */
• return info->cpu_addr;

-}

-static void ion_cma_unmap_kernel(struct ion_heap *heap,

• 		 struct ion_buffer *buffer)
  

-{

• sg_free_table(buffer->sg_table);
• kfree(buffer->sg_table);

}

static struct ion_heap_ops ion_cma_ops = { .allocate = ion_cma_allocate, .free = ion_cma_free,

• .map_user = ion_cma_mmap,
• .map_kernel = ion_cma_map_kernel,
• .unmap_kernel = ion_cma_unmap_kernel,

• .map_user = ion_heap_map_user,
• .map_kernel = ion_heap_map_kernel,
• .unmap_kernel = ion_heap_unmap_kernel,

};

struct ion_heap *ion_cma_heap_create(struct ion_platform_heap *data) @@ -147,7 +102,7 @@ struct ion_heap *ion_cma_heap_create(struct ion_platform_heap *data) * get device from private heaps data, later it will be * used to make the link with reserved CMA memory */

• cma_heap->dev = data->priv;

• cma_heap->cma = data->priv; cma_heap->heap.type = ION_HEAP_TYPE_DMA; return &cma_heap->heap;

}