[PATCH RFC 3/3] riscv: Add SYNC_DMA_FOR_CPU/DEVICE for DMA_COHERENT

guoren
2021-05-19T05:05:39Z

From: Guo Ren <guoren@linux.alibaba.com>

To support DMA device in a non-coherent interconnect SOC system,
we need the below facilities:
- Change a memory region attributes from cacheable to strong.
It would be used in DMA descriptors.
- Sync the cache with memory before DMA start and after DMA end.
It would be used for DMA data transfer buffers.

This patch enables kernel dma/direct.c coherent infrastructure and
a new sbi_ecall API for dma_sync.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Anup Patel <anup.patel@wdc.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Drew Fustini <drew@beagleboard.org>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Wei Fu <wefu@redhat.com>
Cc: Wei Wu <lazyparser@gmail.com>
---
arch/riscv/Kconfig | 4 ++++
arch/riscv/include/asm/pgtable.h | 13 +++++++++++++
arch/riscv/include/asm/sbi.h | 16 ++++++++++++++++
arch/riscv/kernel/sbi.c | 19 +++++++++++++++++++
arch/riscv/mm/Makefile | 4 ++++
arch/riscv/mm/dma-mapping.c | 41 ++++++++++++++++++++++++++++++++++++++++
6 files changed, 97 insertions(+)
create mode 100644 arch/riscv/mm/dma-mapping.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 632fac5..94a736a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -20,6 +20,9 @@ config RISCV
select ARCH_HAS_DEBUG_VM_PGTABLE
select ARCH_HAS_DEBUG_VIRTUAL if MMU
select ARCH_HAS_DEBUG_WX
+ select ARCH_HAS_DMA_PREP_COHERENT if RISCV_DMA_COHERENT
+ select ARCH_HAS_SYNC_DMA_FOR_CPU if RISCV_DMA_COHERENT
+ select ARCH_HAS_SYNC_DMA_FOR_DEVICE if RISCV_DMA_COHERENT
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
select ARCH_HAS_GIGANTIC_PAGE
@@ -41,6 +44,7 @@ config RISCV
select CLONE_BACKWARDS
select CLINT_TIMER if !MMU
select COMMON_CLK
+ select DMA_DIRECT_REMAP if RISCV_DMA_COHERENT
select EDAC_SUPPORT
select GENERIC_ARCH_TOPOLOGY if SMP
select GENERIC_ATOMIC64 if !64BIT
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index f822f22..8994d58 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -465,6 +465,19 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
return ptep_test_and_clear_young(vma, address, ptep);
}

+#ifdef CONFIG_RISCV_DMA_COHERENT
+#define pgprot_noncached pgprot_noncached
+static inline pgprot_t pgprot_noncached(pgprot_t _prot)
+{
+ unsigned long prot = pgprot_val(_prot);
+
+ prot &= ~_PAGE_DMA_MASK;
+ prot |= _PAGE_DMA_NONCACHE;
+
+ return __pgprot(prot);
+}
+#endif
+
/*
* Encode and decode a swap entry
*
diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 0d42693..08b4244 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -27,6 +27,7 @@ enum sbi_ext_id {
SBI_EXT_IPI = 0x735049,
SBI_EXT_RFENCE = 0x52464E43,
SBI_EXT_HSM = 0x48534D,
+ SBI_EXT_DMA = 0xAB150401,
};

enum sbi_ext_base_fid {
@@ -37,6 +38,7 @@ enum sbi_ext_base_fid {
SBI_EXT_BASE_GET_MVENDORID,
SBI_EXT_BASE_GET_MARCHID,
SBI_EXT_BASE_GET_MIMPID,
+ SBI_EXT_RFENCE_REMOTE_DMA_SYNC,
};

enum sbi_ext_time_fid {
@@ -63,6 +65,17 @@ enum sbi_ext_hsm_fid {
SBI_EXT_HSM_HART_STATUS,
};

+enum sbi_ext_dma_fid {
+ SBI_DMA_SYNC = 0,
+};
+
+enum sbi_dma_sync_data_direction {
+ SBI_DMA_BIDIRECTIONAL = 0,
+ SBI_DMA_TO_DEVICE = 1,
+ SBI_DMA_FROM_DEVICE = 2,
+ SBI_DMA_NONE = 3,
+};
+
enum sbi_hsm_hart_status {
SBI_HSM_HART_STATUS_STARTED = 0,
SBI_HSM_HART_STATUS_STOPPED,
@@ -128,6 +141,9 @@ int sbi_remote_hfence_vvma_asid(const unsigned long *hart_mask,
unsigned long size,
unsigned long asid);
int sbi_probe_extension(int ext);
+void sbi_dma_sync(unsigned long start,
+ unsigned long size,
+ enum sbi_dma_sync_data_direction dir);

/* Check if current SBI specification version is 0.1 or not */
static inline int sbi_spec_is_0_1(void)
diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
index 7402a41..ff8e18b 100644
--- a/arch/riscv/kernel/sbi.c
+++ b/arch/riscv/kernel/sbi.c
@@ -521,6 +521,25 @@ int sbi_probe_extension(int extid)
}
EXPORT_SYMBOL(sbi_probe_extension);

+void sbi_dma_sync(unsigned long start,
+ unsigned long size,
+ enum sbi_dma_sync_data_direction dir)
+{
+#if 0
+ sbi_ecall(SBI_EXT_DMA, SBI_DMA_SYNC, start, size, dir,
+ 0, 0, 0);
+#else
+ /* Just for try, it should be in sbi ecall and will be removed before merged */
+ register unsigned long i asm("a0") = start & ~(L1_CACHE_BYTES - 1);
+
+ for (; i < (start + size); i += L1_CACHE_BYTES)
+ __asm__ __volatile__(".long 0x02b5000b");
+
+ __asm__ __volatile__(".long 0x01b0000b");
+#endif
+}
+EXPORT_SYMBOL(sbi_dma_sync);
+
static long __sbi_base_ecall(int fid)
{
struct sbiret ret;
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index 7ebaef1..b67d956 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -14,6 +14,10 @@ obj-$(CONFIG_MMU) += fault.o pageattr.o
obj-y += cacheflush.o
obj-y += context.o

+ifeq ($(CONFIG_RISCV_DMA_COHERENT), y)
+obj-y += dma-mapping.o
+endif
+
ifeq ($(CONFIG_MMU),y)
obj-$(CONFIG_SMP) += tlbflush.o
endif
diff --git a/arch/riscv/mm/dma-mapping.c b/arch/riscv/mm/dma-mapping.c
new file mode 100644
index 00000000..f5db60b
--- /dev/null
+++ b/arch/riscv/mm/dma-mapping.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-map-ops.h>
+#include <asm/sbi.h>
+
+void arch_dma_prep_coherent(struct page *page, size_t size)
+{
+ void *ptr = page_address(page);
+
+ memset(ptr, 0, size);
+ sbi_dma_sync(page_to_phys(page), size, SBI_DMA_BIDIRECTIONAL);
+}
+
+void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
+ enum dma_data_direction dir)
+{
+ switch (dir) {
+ case DMA_TO_DEVICE:
+ case DMA_FROM_DEVICE:
+ case DMA_BIDIRECTIONAL:
+ sbi_dma_sync(paddr, size, dir);
+ break;
+ default:
+ BUG();
+ }
+}
+
+void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
+ enum dma_data_direction dir)
+{
+ switch (dir) {
+ case DMA_TO_DEVICE:
+ return;
+ case DMA_FROM_DEVICE:
+ case DMA_BIDIRECTIONAL:
+ sbi_dma_sync(paddr, size, dir);
+ break;
+ default:
+ BUG();
+ }
+}
--
2.7.4