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>
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
+ select SWIOTLB
endchoice
--- /dev/null
+// 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 */
#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>
setup_bootmem();
paging_init();
unflatten_device_tree();
+ swiotlb_init(1);
#ifdef CONFIG_SMP
setup_smp();