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.

Signed-off-by: Maxime Ripard mripard@kernel.org --- drivers/dma-buf/heaps/cma_heap.c | 19 ++------------ include/linux/dma-buf/heaps/cma.h | 16 ------------ include/linux/dma-map-ops.h | 5 ++++ kernel/dma/contiguous.c | 55 +++++++++++++++++++++++++++++++++++---- 4 files changed, 57 insertions(+), 38 deletions(-)

diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index bd3370b9a3f6d4e18885a1d0e8ba3f659b85ef47..33cac626da1198e3c4a1cdcd562223c1924b6ceb 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -12,11 +12,10 @@

#define pr_fmt(fmt) "cma_heap: " fmt

#include <linux/cma.h> #include <linux/dma-buf.h> -#include <linux/dma-buf/heaps/cma.h> #include <linux/dma-heap.h> #include <linux/dma-map-ops.h> #include <linux/err.h> #include <linux/highmem.h> #include <linux/io.h> @@ -28,23 +27,10 @@ #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 +398,21 @@ 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_area_by_idx(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-buf/heaps/cma.h b/include/linux/dma-buf/heaps/cma.h deleted file mode 100644 index e751479e21e703e24a5f799b4a7fc8bd0df3c1c4..0000000000000000000000000000000000000000 --- a/include/linux/dma-buf/heaps/cma.h +++ /dev/null @@ -1,16 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -#ifndef DMA_BUF_HEAP_CMA_H_ -#define DMA_BUF_HEAP_CMA_H_ - -struct cma; - -#ifdef CONFIG_DMABUF_HEAPS_CMA -int dma_heap_cma_register_heap(struct cma *cma); -#else -static inline int dma_heap_cma_register_heap(struct cma *cma) -{ - return 0; -} -#endif // CONFIG_DMABUF_HEAPS_CMA - -#endif // DMA_BUF_HEAP_CMA_H_ diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h index 60b63756df821d839436618f1fca2bfa3eabe075..c4c93c72ff6ff3ff5c59b7161970805422e9dccb 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -97,10 +97,11 @@ 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 *dma_contiguous_get_area_by_idx(unsigned int idx);

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);

@@ -115,10 +116,14 @@ void dma_contiguous_early_fixup(phys_addr_t base, unsigned long size); #else /* CONFIG_DMA_CMA */ static inline struct cma *dev_get_cma_area(struct device *dev) { return NULL; } +static inline struct cma *dma_contiguous_get_area_by_idx(unsigned int idx) +{ + return NULL; +} static inline void dma_contiguous_reserve(phys_addr_t limit) { } static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, phys_addr_t limit, struct cma **res_cma, diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index c56004d314dc2e436cddf3b20a4ee6ce8178bee4..afa9fd31304051d200cd4396dec26dd50becc375 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -40,21 +40,51 @@ #include <asm/page.h>

#include <linux/memblock.h> #include <linux/err.h> #include <linux/sizes.h> -#include <linux/dma-buf/heaps/cma.h> #include <linux/dma-map-ops.h> #include <linux/cma.h> #include <linux/nospec.h>

#ifdef CONFIG_CMA_SIZE_MBYTES #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES #else #define CMA_SIZE_MBYTES 0 #endif

+static struct cma *dma_contiguous_areas[MAX_CMA_AREAS]; +static unsigned int dma_contiguous_areas_num; + +static int dma_contiguous_insert_area(struct cma *cma) +{ + if (dma_contiguous_areas_num >= ARRAY_SIZE(dma_contiguous_areas)) + return -EINVAL; + + dma_contiguous_areas[dma_contiguous_areas_num++] = cma; + + return 0; +} + +/** + * dma_contiguous_get_area_by_idx() - Get contiguous area at given index + * @idx: index of the area we query + * + * Queries for the contiguous area located at index @idx. + * + * Returns: + * A pointer to the requested contiguous area, or NULL otherwise. + */ +struct cma *dma_contiguous_get_area_by_idx(unsigned int idx) +{ + if (idx >= dma_contiguous_areas_num) + return NULL; + + return dma_contiguous_areas[idx]; +} +EXPORT_SYMBOL_GPL(dma_contiguous_get_area_by_idx); + 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 @@ -262,13 +292,28 @@ void __init dma_contiguous_reserve(phys_addr_t limit) &dma_contiguous_default_area, fixed); if (ret) return;

- ret = dma_heap_cma_register_heap(dma_contiguous_default_area); + /* + * We need to insert the new area in our list to avoid + * any inconsistencies between having the default area + * listed in the DT or not. + * + * The DT case is handled by rmem_cma_setup() and will + * always insert all its areas in our list. However, if + * it didn't run (because OF_RESERVED_MEM isn't set, or + * there's no DT region specified), then we don't have a + * default area yet, and no area in our list. + * + * This block creates the default area in such a case, + * but we also need to insert it in our list to avoid + * having a default area but an empty list. + */ + ret = dma_contiguous_insert_area(dma_contiguous_default_area); if (ret) - pr_warn("Couldn't register default CMA heap."); + pr_warn("Couldn't queue default CMA region for heap creation."); } }

void __weak dma_contiguous_early_fixup(phys_addr_t base, unsigned long size) @@ -504,13 +549,13 @@ 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 = dma_contiguous_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 8604106c0c01b6a9dadc45263f3b1d9ecfacd4aa..bef279ebeae7de59dd504e631f47c64d7e223736 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); struct cma *dma_contiguous_get_area_by_idx(unsigned int idx);

void dma_contiguous_reserve(phys_addr_t addr_limit); int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base, diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 40a0ead24979cfdf25e4779545536a5438e26356..fd8d3518a2323f0a631fb185ef92a24c35f8d25d 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -81,11 +81,11 @@ struct cma *dma_contiguous_get_area_by_idx(unsigned int idx)

return dma_contiguous_areas[idx]; } EXPORT_SYMBOL_GPL(dma_contiguous_get_area_by_idx);

-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 33cac626da1198e3c4a1cdcd562223c1924b6ceb..0ed519a19da455df7441396c96934a107fd72ffb 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -421,5 +421,8 @@ 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");