From 0fd17e5983337231dc655e9ca0095d2ca3f47405 Mon Sep 17 00:00:00 2001 From: Oreoluwa Babatunde Date: Mon, 26 Jan 2026 18:13:27 +0100 Subject: [PATCH] of: reserved_mem: Allow reserved_mem framework detect "cma=" kernel param When initializing the default cma region, the "cma=" kernel parameter takes priority over a DT defined linux,cma-default region. Hence, give the reserved_mem framework the ability to detect this so that the DT defined cma region can skip initialization accordingly. Signed-off-by: Oreoluwa Babatunde Tested-by: Joy Zou Acked-by: Rob Herring (Arm) Fixes: 8a6e02d0c00e ("of: reserved_mem: Restructure how the reserved memory regions are processed") Fixes: 2c223f7239f3 ("of: reserved_mem: Restructure call site for dma_contiguous_early_fixup()") Link: https://lore.kernel.org/r/20251210002027.1171519-1-oreoluwa.babatunde@oss.qualcomm.com [mszyprow: rebased onto v6.19-rc1, added fixes tags, added a stub for cma_skip_dt_default_reserved_mem() if no CONFIG_DMA_CMA is set] Signed-off-by: Marek Szyprowski --- drivers/of/of_reserved_mem.c | 19 +++++++++++++++++-- include/linux/cma.h | 9 +++++++++ kernel/dma/contiguous.c | 16 ++++++++++------ 3 files changed, 36 insertions(+), 8 deletions(-) diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c index 5619ec917858..a2a13617c6f4 100644 --- a/drivers/of/of_reserved_mem.c +++ b/drivers/of/of_reserved_mem.c @@ -157,13 +157,19 @@ static int __init __reserved_mem_reserve_reg(unsigned long node, phys_addr_t base, size; int i, len; const __be32 *prop; - bool nomap; + bool nomap, default_cma; prop = of_flat_dt_get_addr_size_prop(node, "reg", &len); if (!prop) return -ENOENT; nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL; + default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL); + + if (default_cma && cma_skip_dt_default_reserved_mem()) { + pr_err("Skipping dt linux,cma-default for \"cma=\" kernel param.\n"); + return -EINVAL; + } for (i = 0; i < len; i++) { u64 b, s; @@ -248,10 +254,13 @@ void __init fdt_scan_reserved_mem_reg_nodes(void) fdt_for_each_subnode(child, fdt, node) { const char *uname; + bool default_cma = of_get_flat_dt_prop(child, "linux,cma-default", NULL); u64 b, s; if (!of_fdt_device_is_available(fdt, child)) continue; + if (default_cma && cma_skip_dt_default_reserved_mem()) + continue; if (!of_flat_dt_get_addr_size(child, "reg", &b, &s)) continue; @@ -389,7 +398,7 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam phys_addr_t base = 0, align = 0, size; int i, len; const __be32 *prop; - bool nomap; + bool nomap, default_cma; int ret; prop = of_get_flat_dt_prop(node, "size", &len); @@ -413,6 +422,12 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam } nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL; + default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL); + + if (default_cma && cma_skip_dt_default_reserved_mem()) { + pr_err("Skipping dt linux,cma-default for \"cma=\" kernel param.\n"); + return -EINVAL; + } /* Need adjust the alignment to satisfy the CMA requirement */ if (IS_ENABLED(CONFIG_CMA) diff --git a/include/linux/cma.h b/include/linux/cma.h index 62d9c1cf6326..2e6931735880 100644 --- a/include/linux/cma.h +++ b/include/linux/cma.h @@ -57,6 +57,15 @@ extern bool cma_intersects(struct cma *cma, unsigned long start, unsigned long e extern void cma_reserve_pages_on_error(struct cma *cma); +#ifdef CONFIG_DMA_CMA +extern bool cma_skip_dt_default_reserved_mem(void); +#else +static inline bool cma_skip_dt_default_reserved_mem(void) +{ + return false; +} +#endif + #ifdef CONFIG_CMA struct folio *cma_alloc_folio(struct cma *cma, int order, gfp_t gfp); bool cma_free_folio(struct cma *cma, const struct folio *folio); diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index d8fd6f779f79..0e266979728b 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -91,6 +91,16 @@ static int __init early_cma(char *p) } early_param("cma", early_cma); +/* + * cma_skip_dt_default_reserved_mem - This is called from the + * reserved_mem framework to detect if the default cma region is being + * set by the "cma=" kernel parameter. + */ +bool __init cma_skip_dt_default_reserved_mem(void) +{ + return size_cmdline != -1; +} + #ifdef CONFIG_DMA_NUMA_CMA static struct cma *dma_contiguous_numa_area[MAX_NUMNODES]; @@ -470,12 +480,6 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem) struct cma *cma; int err; - if (size_cmdline != -1 && default_cma) { - pr_info("Reserved memory: bypass %s node, using cmdline CMA params instead\n", - rmem->name); - return -EBUSY; - } - if (!of_get_flat_dt_prop(node, "reusable", NULL) || of_get_flat_dt_prop(node, "no-map", NULL)) return -EINVAL; -- 2.47.3