[PATCH 05/12] riscv: Implement non-coherent DMA support via SiFive cache flushing

[Cristian Ciocaltea]

From: Emil Renner Berthing <kernel at esmil.dk>

This variant is used on the StarFive JH7100 SoC.

Signed-off-by: Emil Renner Berthing <kernel at esmil.dk>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
---
 arch/riscv/Kconfig              |  6 ++++--
 arch/riscv/mm/dma-noncoherent.c | 37 +++++++++++++++++++++++++++++++--
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 9c687da7756d..05f6c77faf6f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -232,12 +232,14 @@ config LOCKDEP_SUPPORT
 	def_bool y
 
 config RISCV_DMA_NONCOHERENT
-	bool
+	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
-	select DMA_DIRECT_REMAP
 
 config AS_HAS_INSN
 	def_bool $(as-instr,.insn r 51$(comma) 0$(comma) 0$(comma) t0$(comma) t0$(comma) zero)
diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
index d919efab6eba..e07e53aea537 100644
--- a/arch/riscv/mm/dma-noncoherent.c
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -9,14 +9,21 @@
 #include <linux/dma-map-ops.h>
 #include <linux/mm.h>
 #include <asm/cacheflush.h>
+#include <soc/sifive/sifive_ccache.h>
 
 static bool noncoherent_supported;
 
 void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
 			      enum dma_data_direction dir)
 {
-	void *vaddr = phys_to_virt(paddr);
+	void *vaddr;
 
+	if (sifive_ccache_handle_noncoherent()) {
+		sifive_ccache_flush_range(paddr, size);
+		return;
+	}
+
+	vaddr = phys_to_virt(paddr);
 	switch (dir) {
 	case DMA_TO_DEVICE:
 		ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
@@ -35,8 +42,14 @@ void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
 void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
 			   enum dma_data_direction dir)
 {
-	void *vaddr = phys_to_virt(paddr);
+	void *vaddr;
+
+	if (sifive_ccache_handle_noncoherent()) {
+		sifive_ccache_flush_range(paddr, size);
+		return;
+	}
 
+	vaddr = phys_to_virt(paddr);
 	switch (dir) {
 	case DMA_TO_DEVICE:
 		break;
@@ -49,10 +62,30 @@ void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
 	}
 }
 
+void *arch_dma_set_uncached(void *addr, size_t size)
+{
+	if (sifive_ccache_handle_noncoherent())
+		return sifive_ccache_set_uncached(addr, size);
+
+	return addr;
+}
+
+void arch_dma_clear_uncached(void *addr, size_t size)
+{
+	if (sifive_ccache_handle_noncoherent())
+		sifive_ccache_clear_uncached(addr, size);
+}
+
 void arch_dma_prep_coherent(struct page *page, size_t size)
 {
 	void *flush_addr = page_address(page);
 
+	if (sifive_ccache_handle_noncoherent()) {
+		memset(flush_addr, 0, size);
+		sifive_ccache_flush_range(__pa(flush_addr), size);
+		return;
+	}
+
 	ALT_CMO_OP(flush, flush_addr, size, riscv_cbom_block_size);
 }
 
-- 
2.39.1