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Subject[PATCH v3 3/3] riscv: dma-mapping: switch over to generic implementation
Date
From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

Add helper functions for cache wback/inval/clean and use them
arch_sync_dma_for_device()/arch_sync_dma_for_cpu() functions. The proposed
changes are in preparation for switching over to generic implementation.

Reorganization of the code is based on the patch (Link[0]) from Arnd.
For now I have dropped CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU check as this
will be enabled by default upon selection of RISCV_DMA_NONCOHERENT
and also dropped arch_dma_mark_dcache_clean().

Link[0]: https://lore.kernel.org/all/20230327121317.4081816-22-arnd@kernel.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
Hi Arnd,
I have kept the changes minimal here as compared to your original patch and
dropped arch_dma_mark_dcache_clean() function and config checks for now as we
are currently implementing for riscv only.

Cheers, Prabhakar

v3:
* New patch
---
arch/riscv/mm/dma-noncoherent.c | 60 ++++++++++++++++++++++++++++-----
1 file changed, 51 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
index fc6377a64c8d..06b8fea58e20 100644
--- a/arch/riscv/mm/dma-noncoherent.c
+++ b/arch/riscv/mm/dma-noncoherent.c
@@ -12,21 +12,61 @@

static bool noncoherent_supported __ro_after_init;

-void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
- enum dma_data_direction dir)
+static inline void arch_dma_cache_wback(phys_addr_t paddr, size_t size)
+{
+ void *vaddr = phys_to_virt(paddr);
+
+ ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
+}
+
+static inline void arch_dma_cache_inv(phys_addr_t paddr, size_t size)
+{
+ void *vaddr = phys_to_virt(paddr);
+
+ ALT_CMO_OP(inval, vaddr, size, riscv_cbom_block_size);
+}
+
+static inline void arch_dma_cache_wback_inv(phys_addr_t paddr, size_t size)
{
void *vaddr = phys_to_virt(paddr);

+ ALT_CMO_OP(flush, vaddr, size, riscv_cbom_block_size);
+}
+
+static inline bool arch_sync_dma_clean_before_fromdevice(void)
+{
+ return true;
+}
+
+static inline bool arch_sync_dma_cpu_needs_post_dma_flush(void)
+{
+ return true;
+}
+
+void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
+ enum dma_data_direction dir)
+{
switch (dir) {
case DMA_TO_DEVICE:
- ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
+ arch_dma_cache_wback(paddr, size);
break;
+
case DMA_FROM_DEVICE:
- ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
- break;
+ if (!arch_sync_dma_clean_before_fromdevice()) {
+ arch_dma_cache_inv(paddr, size);
+ break;
+ }
+ fallthrough;
+
case DMA_BIDIRECTIONAL:
- ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
+ /* Skip the invalidate here if it's done later */
+ if (IS_ENABLED(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) &&
+ arch_sync_dma_cpu_needs_post_dma_flush())
+ arch_dma_cache_wback(paddr, size);
+ else
+ arch_dma_cache_wback_inv(paddr, size);
break;
+
default:
break;
}
@@ -35,15 +75,17 @@ 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);
-
switch (dir) {
case DMA_TO_DEVICE:
break;
+
case DMA_FROM_DEVICE:
case DMA_BIDIRECTIONAL:
- ALT_CMO_OP(inval, vaddr, size, riscv_cbom_block_size);
+ /* FROM_DEVICE invalidate needed if speculative CPU prefetch only */
+ if (arch_sync_dma_cpu_needs_post_dma_flush())
+ arch_dma_cache_inv(paddr, size);
break;
+
default:
break;
}
--
2.34.1
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