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

Cristian Ciocaltea
2023-02-11T03:29:16Z

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

This variant is used on the StarFive JH7100 SoC.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@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