The CMA heap instantiation was initially developed by having the contiguous DMA code call into the CMA heap to create a new instance every time a reserved memory area is probed.

Turning the CMA heap into a module would create a dependency of the kernel on a module, which doesn't work.

Let's turn the logic around and do the opposite: store all the reserved memory CMA regions into the contiguous DMA code, and provide an iterator for the heap to use when it probes.

Reviewed-by: T.J. Mercier tjmercier@google.com Reviewed-by: Albert Esteve aesteve@redhat.com Signed-off-by: Maxime Ripard mripard@kernel.org --- drivers/dma-buf/heaps/cma_heap.c | 18 ++---------------- include/linux/dma-map-ops.h | 5 +++++ kernel/dma/contiguous.c | 26 ++++++++++++++++++++++++-- 3 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index bd3370b9a3f6d4e18885a1d0e8ba3f659b85ef47..f8a3d87f3ccee9630383ba28502eb40b10671cc2 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -28,23 +28,10 @@ #include <linux/slab.h> #include <linux/vmalloc.h>

#define DEFAULT_CMA_NAME "default_cma_region"

-static struct cma *dma_areas[MAX_CMA_AREAS] __initdata; -static unsigned int dma_areas_num __initdata; - -int __init dma_heap_cma_register_heap(struct cma *cma) -{ - if (dma_areas_num >= ARRAY_SIZE(dma_areas)) - return -EINVAL; - - dma_areas[dma_areas_num++] = cma; - - return 0; -} - struct cma_heap { struct dma_heap *heap; struct cma *cma; };

@@ -412,22 +399,21 @@ static int __init __add_cma_heap(struct cma *cma, const char *name) }

static int __init add_cma_heaps(void) { struct cma *default_cma = dev_get_cma_area(NULL); + struct cma *cma; unsigned int i; int ret;

if (default_cma) { ret = __add_cma_heap(default_cma, DEFAULT_CMA_NAME); if (ret) return ret; }

- for (i = 0; i < dma_areas_num; i++) { - struct cma *cma = dma_areas[i]; - + for (i = 0; (cma = dma_contiguous_get_reserved_region(i)) != NULL; i++) { ret = __add_cma_heap(cma, cma_get_name(cma)); if (ret) { pr_warn("Failed to add CMA heap %s", cma_get_name(cma)); continue; } diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h index 60b63756df821d839436618f1fca2bfa3eabe075..3007c68a8ec5b85990d1938d04a2f05c1a71acdb 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -110,10 +110,11 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages, int count); struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp); void dma_free_contiguous(struct device *dev, struct page *page, size_t size);

void dma_contiguous_early_fixup(phys_addr_t base, unsigned long size); +struct cma *dma_contiguous_get_reserved_region(unsigned int idx); #else /* CONFIG_DMA_CMA */ static inline struct cma *dev_get_cma_area(struct device *dev) { return NULL; } @@ -148,10 +149,14 @@ static inline void dma_free_contiguous(struct device *dev, struct page *page, __free_pages(page, get_order(size)); } static inline void dma_contiguous_early_fixup(phys_addr_t base, unsigned long size) { } +static inline struct cma *dma_contiguous_get_reserved_region(unsigned int idx) +{ + return NULL; +} #endif /* CONFIG_DMA_CMA*/

#ifdef CONFIG_DMA_DECLARE_COHERENT int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr, dma_addr_t device_addr, size_t size); diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index c56004d314dc2e436cddf3b20a4ee6ce8178bee4..14bd54fb758537f01a6fe27318e7b683964e20b1 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -456,10 +456,32 @@ void dma_free_contiguous(struct device *dev, struct page *page, size_t size) #include <linux/of_reserved_mem.h>

#undef pr_fmt #define pr_fmt(fmt) fmt

+static struct cma *rmem_cma_areas[MAX_CMA_AREAS]; +static unsigned int rmem_cma_areas_num; + +static int rmem_cma_insert_area(struct cma *cma) +{ + if (rmem_cma_areas_num >= ARRAY_SIZE(rmem_cma_areas)) + return -EINVAL; + + rmem_cma_areas[rmem_cma_areas_num++] = cma; + + return 0; +} + +struct cma *dma_contiguous_get_reserved_region(unsigned int idx) +{ + if (idx >= rmem_cma_areas_num) + return NULL; + + return rmem_cma_areas[idx]; +} +EXPORT_SYMBOL_GPL(dma_contiguous_get_reserved_region); + static int rmem_cma_device_init(struct reserved_mem *rmem, struct device *dev) { dev->cma_area = rmem->priv; return 0; } @@ -504,13 +526,13 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem) rmem->priv = cma;

pr_info("Reserved memory: created CMA memory pool at %pa, size %ld MiB\n", &rmem->base, (unsigned long)rmem->size / SZ_1M);

- err = dma_heap_cma_register_heap(cma); + err = rmem_cma_insert_area(cma); if (err) - pr_warn("Couldn't register CMA heap."); + pr_warn("Couldn't store CMA reserved area.");

return 0; } RESERVEDMEM_OF_DECLARE(cma, "shared-dma-pool", rmem_cma_setup); #endif

Now that dev_get_cma_area() is no longer inline, we don't have any user of dma_contiguous_default_area() outside of contiguous.c so we can make it static.

Signed-off-by: Maxime Ripard mripard@kernel.org --- include/linux/dma-map-ops.h | 2 -- kernel/dma/contiguous.c | 2 +- 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h index 6b8e6a2a08e2cb380de764bd6cacb2cb24c22871..94fbf16646c105fa2e1d34d407a830bf989d4fc8 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -89,12 +89,10 @@ static inline void set_dma_ops(struct device *dev, { } #endif /* CONFIG_ARCH_HAS_DMA_OPS */

#ifdef CONFIG_DMA_CMA -extern struct cma *dma_contiguous_default_area; - struct cma *dev_get_cma_area(struct device *dev);

void dma_contiguous_reserve(phys_addr_t addr_limit); int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, phys_addr_t limit, struct cma **res_cma, bool fixed); diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 9a9ed7248fb823105609c5db5a51113e54a40192..a4279d800d4658bf1c33b9b1da100eee1367d42f 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -51,11 +51,11 @@ #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES #else #define CMA_SIZE_MBYTES 0 #endif

-struct cma *dma_contiguous_default_area; +static struct cma *dma_contiguous_default_area;

/* * Default global CMA area size can be defined in kernel's .config. * This is useful mainly for distro maintainers to create a kernel * that works correctly for most supported systems.

The CMA dma-buf heap uses cma_alloc() and cma_release() to allocate and free, respectively, its CMA buffers, and cma_get_name() to get the name of the heap instance it's going to create.

However, these functions are not exported. Since we want to turn the CMA heap into a module, let's export them both.

Reviewed-by: T.J. Mercier tjmercier@google.com Acked-by: David Hildenbrand (Arm) david@kernel.org Signed-off-by: Maxime Ripard mripard@kernel.org --- mm/cma.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/mm/cma.c b/mm/cma.c index 94b5da468a7d719e5144d33b06bcc7619c0fbcc9..550effb9c4e01cc488b5744fe61d55a5b70a6d6c 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -50,10 +50,11 @@ unsigned long cma_get_size(const struct cma *cma)

const char *cma_get_name(const struct cma *cma) { return cma->name; } +EXPORT_SYMBOL_GPL(cma_get_name);

static unsigned long cma_bitmap_aligned_mask(const struct cma *cma, unsigned int align_order) { if (align_order <= cma->order_per_bit) @@ -949,10 +950,11 @@ struct page *cma_alloc(struct cma *cma, unsigned long count, if (page) set_pages_refcounted(page, count);

return page; } +EXPORT_SYMBOL_GPL(cma_alloc);

static struct cma_memrange *find_cma_memrange(struct cma *cma, const struct page *pages, unsigned long count) { struct cma_memrange *cmr = NULL; @@ -1025,10 +1027,11 @@ bool cma_release(struct cma *cma, const struct page *pages,

__cma_release_frozen(cma, cmr, pages, count);

return true; } +EXPORT_SYMBOL_GPL(cma_release);

bool cma_release_frozen(struct cma *cma, const struct page *pages, unsigned long count) { struct cma_memrange *cmr;

Now that all the symbols used by the CMA heap are exported, turning the CMA heap into a module becomes pretty easy: we just need to add the usual MODULE_* macros, import the proper namespaces and change the Kconfig symbol to a tristate.

This heap won't be able to unload though, since we're missing a lot of infrastructure to make it safe.

Reviewed-by: T.J. Mercier tjmercier@google.com Signed-off-by: Maxime Ripard mripard@kernel.org --- drivers/dma-buf/heaps/Kconfig | 2 +- drivers/dma-buf/heaps/cma_heap.c | 3 +++ 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c422644e8aadaf5aff2bd9a33c49c1ba3..aed0b9b4febf388376cfc41be9843980d010c4e8 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -4,11 +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" + tristate "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/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index f8a3d87f3ccee9630383ba28502eb40b10671cc2..7216a14262b04bb6130ddf26b7d009f7d15b03fd 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -422,5 +422,8 @@ static int __init add_cma_heaps(void)

return 0; } module_init(add_cma_heaps); MODULE_DESCRIPTION("DMA-BUF CMA Heap"); +MODULE_LICENSE("GPL"); +MODULE_IMPORT_NS("DMA_BUF"); +MODULE_IMPORT_NS("DMA_BUF_HEAP");