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 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

As we try to enable dma-buf heaps, and the CMA one in particular, to compile as modules, we need to export dev_get_cma_area(). It's currently implemented as an inline function that returns either the content of device->cma_area or dma_contiguous_default_area.

Thus, it means we need to export dma_contiguous_default_area, which isn't really something we want any module to have access to.

Instead, let's make dev_get_cma_area() a proper function we will be able to export so we can avoid exporting dma_contiguous_default_area.

Signed-off-by: Maxime Ripard mripard@kernel.org --- include/linux/dma-map-ops.h | 7 +------ kernel/dma/contiguous.c | 8 ++++++++ 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h index 3007c68a8ec5b85990d1938d04a2f05c1a71acdb..dc7d54ac5dd66bd22ef868d7894cc1cb2ee4c156 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -91,16 +91,11 @@ 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;

-static inline struct cma *dev_get_cma_area(struct device *dev) -{ - if (dev && dev->cma_area) - return dev->cma_area; - return 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 14bd54fb758537f01a6fe27318e7b683964e20b1..9a9ed7248fb823105609c5db5a51113e54a40192 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -99,10 +99,18 @@ early_param("cma", early_cma); bool __init cma_skip_dt_default_reserved_mem(void) { return size_cmdline != -1; }

+struct cma *dev_get_cma_area(struct device *dev) +{ + if (dev && dev->cma_area) + return dev->cma_area; + + return dma_contiguous_default_area; +} + #ifdef CONFIG_DMA_NUMA_CMA

static struct cma *dma_contiguous_numa_area[MAX_NUMNODES]; static phys_addr_t numa_cma_size[MAX_NUMNODES] __initdata; static struct cma *dma_contiguous_pernuma_area[MAX_NUMNODES];

The CMA dma-buf heap uses the dev_get_cma_area() function to retrieve the default contiguous area.

Now that this function is no longer inlined, and since we want to turn the CMA heap into a module, let's export it.

Signed-off-by: Maxime Ripard mripard@kernel.org --- kernel/dma/contiguous.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index a4279d800d4658bf1c33b9b1da100eee1367d42f..ad50512d71d3088a73e4b1ac02d6e6122374888e 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -106,10 +106,11 @@ struct cma *dev_get_cma_area(struct device *dev) if (dev && dev->cma_area) return dev->cma_area;

return dma_contiguous_default_area; } +EXPORT_SYMBOL_GPL(dev_get_cma_area);

#ifdef CONFIG_DMA_NUMA_CMA

static struct cma *dma_contiguous_numa_area[MAX_NUMNODES]; static phys_addr_t numa_cma_size[MAX_NUMNODES] __initdata;

The CMA dma-buf heap uses the cma_get_name() function to get the name of the heap instance it's going to create.

However, this function is not exported. Since we want to turn the CMA heap into a module, let's export it.

Reviewed-by: T.J. Mercier tjmercier@google.com Signed-off-by: Maxime Ripard mripard@kernel.org --- mm/cma.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/mm/cma.c b/mm/cma.c index be142b473f3bd41b9c7d8ba4397f018f6993d962..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)

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");

The system heap can be easily turned into a module by adding the usual MODULE_* macros, importing the proper namespaces and changing 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/system_heap.c | 5 +++++ 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index aed0b9b4febf388376cfc41be9843980d010c4e8..e273fb18feca091ccd9b406e68f86c12efb339e9 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -1,7 +1,7 @@ config DMABUF_HEAPS_SYSTEM - bool "DMA-BUF System Heap" + tristate "DMA-BUF System Heap" depends on DMABUF_HEAPS 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.

diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c index b3650d8fd6511a4a755612cfe3a9d9fee796f80e..1957403b0f2ae5e82ab39f5945dfe82808e93964 100644 --- a/drivers/dma-buf/heaps/system_heap.c +++ b/drivers/dma-buf/heaps/system_heap.c @@ -442,5 +442,10 @@ static int __init system_heap_create(void) return PTR_ERR(sys_heap);

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