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Date:   Wed, 6 Mar 2019 17:05:30 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        Brian Starkey <Brian.Starkey@....com>,
        "Andrew F . Davis" <afd@...com>, Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC][PATCH 4/5 v2] dma-buf: heaps: Add CMA heap to dmabuf heapss

Le mar. 5 mars 2019 à 21:54, John Stultz <john.stultz@...aro.org> a écrit :
>
> This adds a CMA heap, which allows userspace to allocate
> a dma-buf of contiguous memory out of a CMA region.
>
> This code is an evolution of the Android ION implementation, so
> thanks to its original author and maintainters:
>   Benjamin Gaignard, Laura Abbott, and others!
>
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Benjamin Gaignard <benjamin.gaignard@...aro.org>
> Cc: Greg KH <gregkh@...uxfoundation.org>
> Cc: Sumit Semwal <sumit.semwal@...aro.org>
> Cc: Liam Mark <lmark@...eaurora.org>
> Cc: Brian Starkey <Brian.Starkey@....com>
> Cc: Andrew F. Davis <afd@...com>
> Cc: Chenbo Feng <fengc@...gle.com>
> Cc: Alistair Strachan <astrachan@...gle.com>
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
> v2:
> * Switch allocate to return dmabuf fd
> * Simplify init code
> * Checkpatch fixups
> ---
>  drivers/dma-buf/heaps/Kconfig    |   8 ++
>  drivers/dma-buf/heaps/Makefile   |   1 +
>  drivers/dma-buf/heaps/cma_heap.c | 164 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 173 insertions(+)
>  create mode 100644 drivers/dma-buf/heaps/cma_heap.c
>
> diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
> index 2050527..a5eef06 100644
> --- a/drivers/dma-buf/heaps/Kconfig
> +++ b/drivers/dma-buf/heaps/Kconfig
> @@ -4,3 +4,11 @@ config DMABUF_HEAPS_SYSTEM
>         help
>           Choose this option to enable the system dmabuf heap. The system heap
>           is backed by pages from the buddy allocator. If in doubt, say Y.
> +
> +config DMABUF_HEAPS_CMA
> +       bool "DMA-BUF CMA Heap"
> +       depends on DMABUF_HEAPS && DMA_CMA
> +       help
> +         Choose this option to enable dma-buf CMA heap. 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/dma-buf/heaps/Makefile b/drivers/dma-buf/heaps/Makefile
> index d1808ec..6e54cde 100644
> --- a/drivers/dma-buf/heaps/Makefile
> +++ b/drivers/dma-buf/heaps/Makefile
> @@ -1,3 +1,4 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-y                                  += heap-helpers.o
>  obj-$(CONFIG_DMABUF_HEAPS_SYSTEM)      += system_heap.o
> +obj-$(CONFIG_DMABUF_HEAPS_CMA)         += cma_heap.o
> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> new file mode 100644
> index 0000000..33c18ec
> --- /dev/null
> +++ b/drivers/dma-buf/heaps/cma_heap.c
> @@ -0,0 +1,164 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * DMABUF CMA heap exporter
> + *
> + * Copyright (C) 2012, 2019 Linaro Ltd.
> + * Author: <benjamin.gaignard@...aro.org> for ST-Ericsson.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/dma-buf.h>
> +#include <linux/dma-heap.h>
> +#include <linux/slab.h>
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/cma.h>
> +#include <linux/scatterlist.h>
> +#include <linux/highmem.h>
> +
> +#include "heap-helpers.h"
> +
> +struct cma_heap {
> +       struct dma_heap heap;
> +       struct cma *cma;
> +};
> +
> +
> +#define to_cma_heap(x) container_of(x, struct cma_heap, heap)

Even if I had write this macro years ago, now I would prefer to have a
static inline function
to be able to check the types.

with that:
Reviewed-by: Benjamin Gaignard <benjamin.gaignard@...aro.org>

> +
> +
> +static void cma_heap_free(struct heap_helper_buffer *buffer)
> +{
> +       struct cma_heap *cma_heap = to_cma_heap(buffer->heap_buffer.heap);
> +       struct page *pages = buffer->priv_virt;
> +       unsigned long nr_pages;
> +
> +       nr_pages = PAGE_ALIGN(buffer->heap_buffer.size) >> PAGE_SHIFT;
> +
> +       /* release memory */
> +       cma_release(cma_heap->cma, pages, nr_pages);
> +       /* release sg table */
> +       sg_free_table(buffer->sg_table);
> +       kfree(buffer->sg_table);
> +       kfree(buffer);
> +}
> +
> +/* dmabuf heap CMA operations functions */
> +static int cma_heap_allocate(struct dma_heap *heap,
> +                               unsigned long len,
> +                               unsigned long flags)
> +{
> +       struct cma_heap *cma_heap = to_cma_heap(heap);
> +       struct heap_helper_buffer *helper_buffer;
> +       struct sg_table *table;
> +       struct page *pages;
> +       size_t size = PAGE_ALIGN(len);
> +       unsigned long nr_pages = size >> PAGE_SHIFT;
> +       unsigned long align = get_order(size);
> +       DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> +       struct dma_buf *dmabuf;
> +       int ret = -ENOMEM;
> +
> +       if (align > CONFIG_CMA_ALIGNMENT)
> +               align = CONFIG_CMA_ALIGNMENT;
> +
> +       helper_buffer = kzalloc(sizeof(*helper_buffer), GFP_KERNEL);
> +       if (!helper_buffer)
> +               return -ENOMEM;
> +
> +       INIT_HEAP_HELPER_BUFFER(helper_buffer, cma_heap_free);
> +       helper_buffer->heap_buffer.flags = flags;
> +       helper_buffer->heap_buffer.heap = heap;
> +       helper_buffer->heap_buffer.size = len;
> +
> +
> +       pages = cma_alloc(cma_heap->cma, nr_pages, align, false);
> +       if (!pages)
> +               goto free_buf;
> +
> +       if (PageHighMem(pages)) {
> +               unsigned long nr_clear_pages = nr_pages;
> +               struct page *page = pages;
> +
> +               while (nr_clear_pages > 0) {
> +                       void *vaddr = kmap_atomic(page);
> +
> +                       memset(vaddr, 0, PAGE_SIZE);
> +                       kunmap_atomic(vaddr);
> +                       page++;
> +                       nr_clear_pages--;
> +               }
> +       } else {
> +               memset(page_address(pages), 0, size);
> +       }
> +
> +       table = kmalloc(sizeof(*table), GFP_KERNEL);
> +       if (!table)
> +               goto free_cma;
> +
> +       ret = sg_alloc_table(table, 1, GFP_KERNEL);
> +       if (ret)
> +               goto free_table;
> +
> +       sg_set_page(table->sgl, pages, size, 0);
> +
> +       /* create the dmabuf */
> +       exp_info.ops = &heap_helper_ops;
> +       exp_info.size = len;
> +       exp_info.flags = O_RDWR;
> +       exp_info.priv = &helper_buffer->heap_buffer;
> +       dmabuf = dma_buf_export(&exp_info);
> +       if (IS_ERR(dmabuf)) {
> +               ret = PTR_ERR(dmabuf);
> +               goto free_table;
> +       }
> +
> +       helper_buffer->heap_buffer.dmabuf = dmabuf;
> +       helper_buffer->priv_virt = pages;
> +       helper_buffer->sg_table = table;
> +
> +       ret = dma_buf_fd(dmabuf, O_CLOEXEC);
> +       if (ret < 0) {
> +               dma_buf_put(dmabuf);
> +               /* just return, as put will call release and that will free */
> +               return ret;
> +       }
> +
> +       return ret;
> +free_table:
> +       kfree(table);
> +free_cma:
> +       cma_release(cma_heap->cma, pages, nr_pages);
> +free_buf:
> +       kfree(helper_buffer);
> +       return ret;
> +}
> +
> +static struct dma_heap_ops cma_heap_ops = {
> +       .allocate = cma_heap_allocate,
> +};
> +
> +static int __add_cma_heaps(struct cma *cma, void *data)
> +{
> +       struct cma_heap *cma_heap;
> +
> +       cma_heap = kzalloc(sizeof(*cma_heap), GFP_KERNEL);
> +
> +       if (!cma_heap)
> +               return -ENOMEM;
> +
> +       cma_heap->heap.name = cma_get_name(cma);
> +       cma_heap->heap.ops = &cma_heap_ops;
> +       cma_heap->cma = cma;
> +
> +       dma_heap_add(&cma_heap->heap);
> +
> +       return 0;
> +}
> +
> +static int add_cma_heaps(void)
> +{
> +       cma_for_each_area(__add_cma_heaps, NULL);
> +       return 0;
> +}
> +device_initcall(add_cma_heaps);
> --
> 2.7.4
>


-- 
Benjamin Gaignard

Graphic Study Group

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