RISC-V: Add non-coherent DMA support

This implements the cache management operations to support non-coherent
DMAs on RISC-V.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>

4 files changed, 67 insertions, 0 deletions

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 696279ce03c9..e96c8a27c140 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -218,6 +218,16 @@ config PGTABLE_LEVELS
 config LOCKDEP_SUPPORT
 	def_bool y
 
+config RISCV_DMA_NONCOHERENT
+	bool "Support non-coherent DMA"
+	default SOC_STARFIVE
+	select ARCH_HAS_DMA_PREP_COHERENT
+	select ARCH_HAS_DMA_SET_UNCACHED
+	select ARCH_HAS_DMA_CLEAR_UNCACHED
+	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
+	select ARCH_HAS_SYNC_DMA_FOR_CPU
+	select ARCH_HAS_SETUP_DMA_OPS
+
 source "arch/riscv/Kconfig.socs"
 source "arch/riscv/Kconfig.erratas"
 
diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
index 9b58b104559e..d3036df23ccb 100644
--- a/arch/riscv/include/asm/cache.h
+++ b/arch/riscv/include/asm/cache.h
@@ -11,6 +11,10 @@
 
 #define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
 
+#ifdef CONFIG_RISCV_DMA_NONCOHERENT
+#define ARCH_DMA_MINALIGN L1_CACHE_BYTES
+#endif
+
 /*
  * RISC-V requires the stack pointer to be 16-byte aligned, so ensure that
  * the flat loader aligns it accordingly.
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index ac7a25298a04..d76aabf4b94d 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -30,3 +30,4 @@ endif
 endif
 
 obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
+obj-$(CONFIG_RISCV_DMA_NONCOHERENT) += dma-noncoherent.o
diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
new file mode 100644
index 000000000000..86d23046b958
--- /dev/null
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * RISC-V specific functions to support DMA for non-coherent devices
+ *
+ * Copyright (c) 2021 Western Digital Corporation or its affiliates.
+ */
+
+#include <linux/dma-map-ops.h>
+
+#include <soc/sifive/sifive_l2_cache.h>
+
+void arch_sync_dma_for_device(phys_addr_t paddr, size_t size, enum dma_data_direction dir)
+{
+	if (sifive_l2_handle_noncoherent())
+		sifive_l2_flush_range(paddr, size);
+}
+
+void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size, enum dma_data_direction dir)
+{
+	if (sifive_l2_handle_noncoherent())
+		sifive_l2_flush_range(paddr, size);
+}
+
+void *arch_dma_set_uncached(void *addr, size_t size)
+{
+	if (sifive_l2_handle_noncoherent())
+		return sifive_l2_set_uncached(addr, size);
+
+	return addr;
+}
+
+void arch_dma_clear_uncached(void *addr, size_t size)
+{
+	if (sifive_l2_handle_noncoherent())
+		sifive_l2_clear_uncached(addr, size);
+}
+
+void arch_dma_prep_coherent(struct page *page, size_t size)
+{
+	void *flush_addr = page_address(page);
+
+	memset(flush_addr, 0, size);
+	if (sifive_l2_handle_noncoherent())
+		sifive_l2_flush_range(__pa(flush_addr), size);
+}
+
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+		const struct iommu_ops *iommu, bool coherent)
+{
+	/* If a specific device is dma-coherent, set it here */
+	dev->dma_coherent = coherent;
+}