Re: [PATCHv3 13/22] staging: android: ion: Use CMA APIs directly

Laurent Pinchart
2017-04-11T06:46:22Z

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 ?

> 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;
> }

--
Regards,

Laurent Pinchart