From: Maxime Ripard Date: Tue, 31 Mar 2026 10:00:10 +0000 (+0200) Subject: dma: contiguous: Turn heap registration logic around X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=25bd73562941b04cfba1a278d8c84f2b1c69b8e9;p=thirdparty%2Fkernel%2Flinux.git dma: contiguous: Turn heap registration logic around 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 Signed-off-by: Marek Szyprowski Link: https://lore.kernel.org/r/20260331-dma-buf-heaps-as-modules-v4-1-e18fda504419@kernel.org --- diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index bd3370b9a3f6d..33cac626da119 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -14,7 +14,6 @@ #include #include -#include #include #include #include @@ -30,19 +29,6 @@ #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; @@ -414,6 +400,7 @@ 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; @@ -423,9 +410,7 @@ static int __init add_cma_heaps(void) 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)); diff --git a/include/linux/dma-buf/heaps/cma.h b/include/linux/dma-buf/heaps/cma.h deleted file mode 100644 index e751479e21e70..0000000000000 --- 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 60b63756df821..c4c93c72ff6ff 100644 --- a/include/linux/dma-map-ops.h +++ b/include/linux/dma-map-ops.h @@ -99,6 +99,7 @@ static inline struct cma *dev_get_cma_area(struct device *dev) 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, @@ -117,6 +118,10 @@ 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) { } diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index c56004d314dc2..afa9fd3130405 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -42,7 +42,6 @@ #include #include #include -#include #include #include #include @@ -53,6 +52,37 @@ #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; /* @@ -264,9 +294,24 @@ void __init dma_contiguous_reserve(phys_addr_t limit) 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."); } } @@ -506,9 +551,9 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem) 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; }