Re: [RFC][PATCH 4/5 v4] dma-buf: heaps: Add CMA heap to dmabuf heaps

[Benjamin Gaignard]

Le mar. 14 mai 2019 Ã 12:40, Xiaqing (A) <saberlily.xia@xxxxxxxxxxxxx> a Ãcrit :
>
>
>
> On 2019/5/14 2:37, John Stultz wrote:
> > 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@xxxxxxxxxx>
> > Cc: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx>
> > Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> > Cc: Liam Mark <lmark@xxxxxxxxxxxxxx>
> > Cc: Pratik Patel <pratikp@xxxxxxxxxxxxxx>
> > Cc: Brian Starkey <Brian.Starkey@xxxxxxx>
> > Cc: Vincent Donnefort <Vincent.Donnefort@xxxxxxx>
> > Cc: Sudipto Paul <Sudipto.Paul@xxxxxxx>
> > Cc: Andrew F. Davis <afd@xxxxxx>
> > Cc: Xu YiPing <xuyiping@xxxxxxxxxxxxx>
> > Cc: "Chenfeng (puck)" <puck.chen@xxxxxxxxxxxxx>
> > Cc: butao <butao@xxxxxxxxxxxxx>
> > Cc: "Xiaqing (A)" <saberlily.xia@xxxxxxxxxxxxx>
> > Cc: Yudongbin <yudongbin@xxxxxxxxxxxxx>
> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> > Cc: Chenbo Feng <fengc@xxxxxxxxxx>
> > Cc: Alistair Strachan <astrachan@xxxxxxxxxx>
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
> > ---
> > v2:
> > * Switch allocate to return dmabuf fd
> > * Simplify init code
> > * Checkpatch fixups
> > v3:
> > * Switch to inline function for to_cma_heap()
> > * Minor cleanups suggested by Brian
> > * Fold in new registration style from Andrew
> > * Folded in changes from Andrew to use simplified page list
> >    from the heap helpers
> > * Use the fd_flags when creating dmabuf fd (Suggested by
> >    Benjamin)
> > * Use precalculated pagecount (Suggested by Andrew)
> > ---
> >   drivers/dma-buf/heaps/Kconfig    |   8 ++
> >   drivers/dma-buf/heaps/Makefile   |   1 +
> >   drivers/dma-buf/heaps/cma_heap.c | 169 +++++++++++++++++++++++++++++++
> >   3 files changed, 178 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 205052744169..a5eef06c4226 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 d1808eca2581..6e54cdec3da0 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 000000000000..3d0ffbbd0a34
> > --- /dev/null
> > +++ b/drivers/dma-buf/heaps/cma_heap.c
> > @@ -0,0 +1,169 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * DMABUF CMA heap exporter
> > + *
> > + * Copyright (C) 2012, 2019 Linaro Ltd.
> > + * Author: <benjamin.gaignard@xxxxxxxxxx> 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;
> > +};
> > +
> > +static void cma_heap_free(struct heap_helper_buffer *buffer)
> > +{
> > +     struct cma_heap *cma_heap = dma_heap_get_data(buffer->heap_buffer.heap);
> > +     unsigned long nr_pages = buffer->pagecount;
> > +     struct page *pages = buffer->priv_virt;
> > +
> > +     /* free page list */
> > +     kfree(buffer->pages);
> > +     /* release memory */
> > +     cma_release(cma_heap->cma, pages, nr_pages);
> > +     kfree(buffer);
> > +}
> > +
> > +/* dmabuf heap CMA operations functions */
> > +static int cma_heap_allocate(struct dma_heap *heap,
> > +                             unsigned long len,
> > +                             unsigned long fd_flags,
> > +                             unsigned long heap_flags)
> > +{
> > +     struct cma_heap *cma_heap = dma_heap_get_data(heap);
> > +     struct heap_helper_buffer *helper_buffer;
> > +     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;
> > +     pgoff_t pg;
> > +
> > +     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 = heap_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);
> > +     }
> > +
> > +     helper_buffer->pagecount = nr_pages;
> > +     helper_buffer->pages = kmalloc_array(helper_buffer->pagecount,
> > +                                          sizeof(*helper_buffer->pages),
> > +                                          GFP_KERNEL);
> > +     if (!helper_buffer->pages) {
> > +             ret = -ENOMEM;
> > +             goto free_cma;
> > +     }
> > +
> > +     for (pg = 0; pg < helper_buffer->pagecount; pg++) {
> > +             helper_buffer->pages[pg] = &pages[pg];
> > +             if (!helper_buffer->pages[pg])
> > +                     goto free_pages;
> > +     }
> > +
> > +     /* create the dmabuf */
> > +     exp_info.ops = &heap_helper_ops;
> > +     exp_info.size = len;
> > +     exp_info.flags = fd_flags;
> > +     exp_info.priv = &helper_buffer->heap_buffer;
> > +     dmabuf = dma_buf_export(&exp_info);
> > +     if (IS_ERR(dmabuf)) {
> > +             ret = PTR_ERR(dmabuf);
> > +             goto free_pages;
> > +     }
> Can the dmabuf be created in the framework layer?
> each heap needs to add the same code here, which is not very good.

No that would make errors cases more difficult to handle because
you will need to call a new heap's function to clean everything.

>
> > +
> > +     helper_buffer->heap_buffer.dmabuf = dmabuf;
> > +     helper_buffer->priv_virt = pages;
> > +
> > +     ret = dma_buf_fd(dmabuf, fd_flags);
> > +     if (ret < 0) {
> > +             dma_buf_put(dmabuf);
> > +             /* just return, as put will call release and that will free */
> > +             return ret;
> > +     }
> > +
> > +     return ret;
> > +
> > +free_pages:
> > +     kfree(helper_buffer->pages);
> > +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_heap(struct cma *cma, void *data)
> > +{
> > +     struct cma_heap *cma_heap;
> > +     struct dma_heap_export_info exp_info;
> > +
> > +     cma_heap = kzalloc(sizeof(*cma_heap), GFP_KERNEL);
> > +     if (!cma_heap)
> > +             return -ENOMEM;
> > +     cma_heap->cma = cma;
> > +
> > +     exp_info.name = cma_get_name(cma);
> > +     exp_info.ops = &cma_heap_ops;
> > +     exp_info.priv = cma_heap;
> > +
> > +     cma_heap->heap = dma_heap_add(&exp_info);
> > +     if (IS_ERR(cma_heap->heap)) {
> > +             int ret = PTR_ERR(cma_heap->heap);
> > +
> > +             kfree(cma_heap);
> > +             return ret;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static int add_cma_heaps(void)
> > +{
> > +     cma_for_each_area(__add_cma_heap, NULL);
> > +     return 0;
> > +}
> > +device_initcall(add_cma_heaps);
> >
>