Currently, linux,dma-default is used to reserve a global non-coherent pool to allocate memory for dma operations. This can be useful for RISC-V as well as the ISA specification doesn't specify a method to modify PMA attributes or page table entries to define non-cacheable area yet. A non-cacheable memory window is an alternate options for vendors to support non-coherent devices. "dma-ranges" must be used in conjunction with "linux,dma-default" property to define one or more mappings between device and cpu accesible memory regions.
This allows RISC-V to use global pool for non-coherent platforms that relies on a uncached memory region that is outside of the system ram. Signed-off-by: Atish Patra <[email protected]> --- kernel/dma/coherent.c | 49 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 41 insertions(+), 8 deletions(-) diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c index 97677df5408b..d0b33b1a76f0 100644 --- a/kernel/dma/coherent.c +++ b/kernel/dma/coherent.c @@ -9,6 +9,8 @@ #include <linux/module.h> #include <linux/dma-direct.h> #include <linux/dma-map-ops.h> +#include <linux/of_address.h> +#include <linux/libfdt.h> struct dma_coherent_mem { void *virt_base; @@ -302,19 +304,27 @@ int dma_mmap_from_global_coherent(struct vm_area_struct *vma, void *vaddr, vaddr, size, ret); } -int dma_init_global_coherent(phys_addr_t phys_addr, size_t size) +static int __dma_init_global_coherent(phys_addr_t phys_addr, dma_addr_t device_addr, size_t size) { struct dma_coherent_mem *mem; - mem = dma_init_coherent_memory(phys_addr, phys_addr, size, true); + if (phys_addr == device_addr) + mem = dma_init_coherent_memory(phys_addr, device_addr, size, true); + else + mem = dma_init_coherent_memory(phys_addr, device_addr, size, false); + if (IS_ERR(mem)) return PTR_ERR(mem); dma_coherent_default_memory = mem; pr_info("DMA: default coherent area is set\n"); return 0; } -#endif /* CONFIG_DMA_GLOBAL_POOL */ +int dma_init_global_coherent(phys_addr_t phys_addr, size_t size) +{ + return __dma_init_global_coherent(phys_addr, phys_addr, size); +} +#endif /* CONFIG_DMA_GLOBAL_POOL */ /* * Support for reserved memory regions defined in device tree */ @@ -329,8 +339,8 @@ static int rmem_dma_device_init(struct reserved_mem *rmem, struct device *dev) if (!rmem->priv) { struct dma_coherent_mem *mem; - mem = dma_init_coherent_memory(rmem->base, rmem->base, - rmem->size, true); + mem = dma_init_coherent_memory(rmem->base, rmem->base, rmem->size, true); + if (IS_ERR(mem)) return PTR_ERR(mem); rmem->priv = mem; @@ -358,7 +368,7 @@ static int __init rmem_dma_setup(struct reserved_mem *rmem) if (of_get_flat_dt_prop(node, "reusable", NULL)) return -EINVAL; -#ifdef CONFIG_ARM +#if defined(CONFIG_ARM) || defined(CONFIG_RISCV) if (!of_get_flat_dt_prop(node, "no-map", NULL)) { pr_err("Reserved memory: regions without no-map are not yet supported\n"); return -EINVAL; @@ -382,10 +392,33 @@ static int __init rmem_dma_setup(struct reserved_mem *rmem) #ifdef CONFIG_DMA_GLOBAL_POOL static int __init dma_init_reserved_memory(void) { + struct device_node *np; + const struct bus_dma_region *map = NULL; + int ret; + int64_t uc_offset = 0; + if (!dma_reserved_default_memory) return -ENOMEM; - return dma_init_global_coherent(dma_reserved_default_memory->base, - dma_reserved_default_memory->size); + + /* dma-ranges is only valid for global pool i.e. dma-default is set */ + np = of_find_node_with_property(NULL, "linux,dma-default"); + if (!np) + goto global_init; + of_node_put(np); + + ret = of_dma_get_range(np, &map); + if (ret < 0) + goto global_init; + + /* Sanity check for the non-coherent global pool from uncached region */ + if (map->dma_start == dma_reserved_default_memory->base && + map->size == dma_reserved_default_memory->size) + uc_offset = map->offset; + +global_init: + return __dma_init_global_coherent(dma_reserved_default_memory->base + uc_offset, + dma_reserved_default_memory->base, + dma_reserved_default_memory->size); } core_initcall(dma_init_reserved_memory); #endif /* CONFIG_DMA_GLOBAL_POOL */ -- 2.31.1 _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
