Re: [RFC PATCH v2 07/11] riscv: cmo: Add dma-noncoherency support

Guo Ren
2021-10-20T08:11:29Z

On Sun, Oct 17, 2021 at 5:28 PM twd2 <twd2.me@gmail.com> wrote:
>
>
> On 2021/6/6 17:04, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > To support DMA device in a non-coherent interconnect SOC system,
> > we need the below facilities:
> > - Changing a virtual memory mapping region attributes from
> > cacheable to noncache + strong order which used in DMA
> > descriptors.
> > - Add noncache + weakorder virtual memory attributes for dma
> > mapping.
> > - Syncing the cache with memory before DMA start and after DMA
> > end with vendor custom CMO instructions.
> >
> > This patch enables linux kernel generic dma-noncoherency
> > infrastructure and introduces new sbi_ecall API for dma_sync.
> >
> > @@ -27,6 +27,7 @@ enum sbi_ext_id {
> > + SBI_EXT_DMA = 0xAB150401,
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Signed-off-by: Liu Shaohua <liush@allwinnertech.com>
> > Cc: Palmer Dabbelt <palmerdabbelt@google.com>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Anup Patel <anup.patel@wdc.com>
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Drew Fustini <drew@beagleboard.org>
> > Cc: Wei Fu <wefu@redhat.com>
> > Cc: Wei Wu <lazyparser@gmail.com>
> > Cc: Chen-Yu Tsai <wens@csie.org>
> > Cc: Maxime Ripard <maxime@cerno.tech>
> > ---
> > arch/riscv/Kconfig | 5 ++++
> > arch/riscv/include/asm/pgtable.h | 26 ++++++++++++++++++++
> > arch/riscv/include/asm/sbi.h | 15 ++++++++++++
> > arch/riscv/kernel/sbi.c | 19 ++++++++++++++
> > arch/riscv/mm/Makefile | 1 +
> > arch/riscv/mm/dma-mapping.c | 53 ++++++++++++++++++++++++++++++++++++++++
> > 6 files changed, 119 insertions(+)
> > create mode 100644 arch/riscv/mm/dma-mapping.c
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 05c4976..817a9bb 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -20,6 +20,10 @@ 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
> > + select ARCH_HAS_SYNC_DMA_FOR_CPU
> > + select ARCH_HAS_SYNC_DMA_FOR_DEVICE
> > + select ARCH_HAS_DMA_WRITE_COMBINE
> > select ARCH_HAS_FORTIFY_SOURCE
> > select ARCH_HAS_GCOV_PROFILE_ALL
> > select ARCH_HAS_GIGANTIC_PAGE
> > @@ -43,6 +47,7 @@ config RISCV
> > select CLONE_BACKWARDS
> > select CLINT_TIMER if !MMU
> > select COMMON_CLK
> > + select DMA_DIRECT_REMAP
> > 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 6ddeb49..e1a82b6 100644
> > --- a/arch/riscv/include/asm/pgtable.h
> > +++ b/arch/riscv/include/asm/pgtable.h
> > @@ -462,6 +462,32 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
> > return ptep_test_and_clear_young(vma, address, ptep);
> > }
> >
> > +#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_IO;
> > +
> > + return __pgprot(prot);
> > +}
> > +
> > +#define pgprot_writecombine pgprot_writecombine
> > +static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
> > +{
> > + unsigned long prot = pgprot_val(_prot);
> > +
> > + prot &= ~_PAGE_DMA_MASK;
> > + prot |= _PAGE_DMA_WC;
> > +
> > + return __pgprot(prot);
> > +}
> > +
> > +#define __HAVE_PHYS_MEM_ACCESS_PROT
> > +extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> > + unsigned long size, pgprot_t vma_prot);
> > +
> > /*
> > * Encode and decode a swap entry
> > *
> > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> > index 0d42693..133e88a 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 {
> > @@ -63,6 +64,17 @@ 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 +140,9 @@ 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..c936019 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 < ALIGN(start + size, L1_CACHE_BYTES); i += L1_CACHE_BYTES)
> > + __asm__ __volatile__(".long 0x02b5000b");
> > +
>
>
> Hi, I'm trying to use this patch for my D1 board.
>
> Though the above code will be removed, I notice that the use of the inline assembly is wrong and `i` (i.e. `a0`) might not be correctly passed to the assembly code when we are using some other compilers.
>
>
> It should be `__asm__ __volatile__(".long 0x02b5000b" : : "r"(i))`.
Yes, I should keep "r"(I).

Thx

>
>
> Thanks,
> Wende
>
>
> > + __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..ca0ff90 100644
> > --- a/arch/riscv/mm/Makefile
> > +++ b/arch/riscv/mm/Makefile
> > @@ -13,6 +13,7 @@ obj-y += extable.o
> > obj-$(CONFIG_MMU) += fault.o pageattr.o
> > obj-y += cacheflush.o
> > obj-y += context.o
> > +obj-y += dma-mapping.o
> >
> > ifeq ($(CONFIG_MMU),y)
> > obj-$(CONFIG_SMP) += tlbflush.o
> > diff --git a/arch/riscv/mm/dma-mapping.c b/arch/riscv/mm/dma-mapping.c
> > new file mode 100644
> > index 00000000..4afd9dc
> > --- /dev/null
> > +++ b/arch/riscv/mm/dma-mapping.c
> > @@ -0,0 +1,53 @@
> > +// 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();
> > + }
> > +}
> > +
> > +pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
> > + unsigned long size, pgprot_t vma_prot)
> > +{
> > + if (!pfn_valid(pfn))
> > + return pgprot_noncached(vma_prot);
> > + else if (file->f_flags & O_SYNC)
> > + return pgprot_writecombine(vma_prot);
> > +
> > + return vma_prot;
> > +}
> > +EXPORT_SYMBOL(phys_mem_access_prot);
>
> --
> Best wishes!
> Sincerely,
> twd2
> https://twd2.me
>

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/