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

[Guo Ren <guoren@kernel.org>]

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/