riscv: add swiotlb support
All RISC-V platforms today lack an IOMMU. However, legacy PCI devices sometimes require DMA-memory to be in the low 32 bits. To make this work, we enable the software-based bounce buffers from swiotlb. They only impose overhead when the device in question cannot address the full 64-bit address space, so a perfect fit. This patch assumes that DMA is coherent with the processor and the PCI bus. It also assumes that the processor and devices share a common address space. This is true for all RISC-V platforms so far. [changelog stolen from an earlier patch by Palmer Dabbelt that did the more complicated swiotlb wireup before the recent consolidation] Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
parent
f1306f0423
commit
10314e09d0
|
@ -114,6 +114,7 @@ config ARCH_RV64I
|
|||
select HAVE_FTRACE_MCOUNT_RECORD
|
||||
select HAVE_DYNAMIC_FTRACE
|
||||
select HAVE_DYNAMIC_FTRACE_WITH_REGS
|
||||
select SWIOTLB
|
||||
|
||||
endchoice
|
||||
|
||||
|
|
15
arch/riscv/include/asm/dma-mapping.h
Normal file
15
arch/riscv/include/asm/dma-mapping.h
Normal file
|
@ -0,0 +1,15 @@
|
|||
// SPDX-License-Identifier: GPL-2.0
|
||||
#ifndef _RISCV_ASM_DMA_MAPPING_H
|
||||
#define _RISCV_ASM_DMA_MAPPING_H 1
|
||||
|
||||
#ifdef CONFIG_SWIOTLB
|
||||
#include <linux/swiotlb.h>
|
||||
static inline const struct dma_map_ops *get_arch_dma_ops(struct bus_type *bus)
|
||||
{
|
||||
return &swiotlb_dma_ops;
|
||||
}
|
||||
#else
|
||||
#include <asm-generic/dma-mapping.h>
|
||||
#endif /* CONFIG_SWIOTLB */
|
||||
|
||||
#endif /* _RISCV_ASM_DMA_MAPPING_H */
|
|
@ -29,6 +29,7 @@
|
|||
#include <linux/of_fdt.h>
|
||||
#include <linux/of_platform.h>
|
||||
#include <linux/sched/task.h>
|
||||
#include <linux/swiotlb.h>
|
||||
|
||||
#include <asm/setup.h>
|
||||
#include <asm/sections.h>
|
||||
|
@ -206,6 +207,7 @@ void __init setup_arch(char **cmdline_p)
|
|||
setup_bootmem();
|
||||
paging_init();
|
||||
unflatten_device_tree();
|
||||
swiotlb_init(1);
|
||||
|
||||
#ifdef CONFIG_SMP
|
||||
setup_smp();
|
||||
|
|
Loading…
Reference in a new issue