[PATCH 19/21] ARM: dma-mapping: use generic form of arch_sync_dma_* helpers

Arnd Bergmann
2023-03-27T12:18:27Z

From: Arnd Bergmann <arnd@arndb.de>

As the final step of the conversion to generic arch_sync_dma_*
helpers, change the Arm implementation to look the same as the
new generic version, by calling the dmac_{clean,inv,flush}_area
low-level functions instead of the abstracted dmac_{map,unmap}_area
version.

On ARMv6/v7, this invalidates the caches after a DMA transfer from
a device because of speculative prefetching, while on earlier versions
it only needs to do this before the transfer.

This should not change any of the current behavior.

FIXME: address CONFIG_DMA_CACHE_RWFO properly.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/arm/mm/dma-mapping-nommu.c | 11 +++----
arch/arm/mm/dma-mapping.c | 53 +++++++++++++++++++++++----------
2 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
index cfd9c933d2f0..12b5c6ae93fc 100644
--- a/arch/arm/mm/dma-mapping-nommu.c
+++ b/arch/arm/mm/dma-mapping-nommu.c
@@ -16,12 +16,13 @@
void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
enum dma_data_direction dir)
{
- dmac_map_area(__va(paddr), size, dir);
-
- if (dir == DMA_FROM_DEVICE)
+ if (dir == DMA_FROM_DEVICE) {
+ dmac_inv_range(__va(paddr), __va(paddr + size));
outer_inv_range(paddr, paddr + size);
- else
+ } else {
+ dmac_clean_range(__va(paddr), __va(paddr + size));
outer_clean_range(paddr, paddr + size);
+ }
}

void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
@@ -29,7 +30,7 @@ void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
{
if (dir != DMA_TO_DEVICE) {
outer_inv_range(paddr, paddr + size);
- dmac_unmap_area(__va(paddr), size, dir);
+ dmac_inv_range(__va(paddr), __va(paddr));
}
}

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index ce4b74f34a58..cc702cb27ae7 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -623,8 +623,7 @@ static void __arm_dma_free(struct device *dev, size_t size, void *cpu_addr,
}

static void dma_cache_maint(phys_addr_t paddr,
- size_t size, enum dma_data_direction dir,
- void (*op)(const void *, size_t, int))
+ size_t size, void (*op)(const void *, const void *))
{
unsigned long pfn = PFN_DOWN(paddr);
unsigned long offset = paddr % PAGE_SIZE;
@@ -647,18 +646,18 @@ static void dma_cache_maint(phys_addr_t paddr,

if (cache_is_vipt_nonaliasing()) {
vaddr = kmap_atomic(page);
- op(vaddr + offset, len, dir);
+ op(vaddr + offset, vaddr + offset + len);
kunmap_atomic(vaddr);
} else {
vaddr = kmap_high_get(page);
if (vaddr) {
- op(vaddr + offset, len, dir);
+ op(vaddr + offset, vaddr + offset + len);
kunmap_high(page);
}
}
} else {
vaddr = page_address(page) + offset;
- op(vaddr, len, dir);
+ op(vaddr, vaddr + len);
}
offset = 0;
pfn++;
@@ -666,6 +665,18 @@ static void dma_cache_maint(phys_addr_t paddr,
} while (left);
}

+static bool arch_sync_dma_cpu_needs_post_dma_flush(void)
+{
+ if (IS_ENABLED(CONFIG_CPU_V6) ||
+ IS_ENABLED(CONFIG_CPU_V6K) ||
+ IS_ENABLED(CONFIG_CPU_V7) ||
+ IS_ENABLED(CONFIG_CPU_V7M))
+ return true;
+
+ /* FIXME: runtime detection */
+ return false;
+}
+
/*
* Make an area consistent for devices.
* Note: Drivers should NOT use this function directly.
@@ -674,25 +685,35 @@ static void dma_cache_maint(phys_addr_t paddr,
void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
enum dma_data_direction dir)
{
- dma_cache_maint(paddr, size, dir, dmac_map_area);
-
- if (dir == DMA_FROM_DEVICE) {
- outer_inv_range(paddr, paddr + size);
- } else {
+ switch (dir) {
+ case DMA_TO_DEVICE:
+ dma_cache_maint(paddr, size, dmac_clean_range);
outer_clean_range(paddr, paddr + size);
+ break;
+ case DMA_FROM_DEVICE:
+ dma_cache_maint(paddr, size, dmac_inv_range);
+ outer_inv_range(paddr, paddr + size);
+ break;
+ case DMA_BIDIRECTIONAL:
+ if (arch_sync_dma_cpu_needs_post_dma_flush()) {
+ dma_cache_maint(paddr, size, dmac_clean_range);
+ outer_clean_range(paddr, paddr + size);
+ } else {
+ dma_cache_maint(paddr, size, dmac_flush_range);
+ outer_flush_range(paddr, paddr + size);
+ }
+ break;
+ default:
+ break;
}
- /* FIXME: non-speculating: flush on bidirectional mappings? */
}

void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
enum dma_data_direction dir)
{
- /* FIXME: non-speculating: not required */
- /* in any case, don't bother invalidating if DMA to device */
- if (dir != DMA_TO_DEVICE) {
+ if (dir != DMA_TO_DEVICE && arch_sync_dma_cpu_needs_post_dma_flush()) {
outer_inv_range(paddr, paddr + size);
-
- dma_cache_maint(paddr, size, dir, dmac_unmap_area);
+ dma_cache_maint(paddr, size, dmac_inv_range);
}

/*
--
2.39.2