Re: [PATCH v11 3/6] riscv: mm: dma-noncoherent: nonstandard cache operations support

[Lad, Prabhakar]

Hi Emil,

Thank you for the review.

On Thu, Aug 17, 2023 at 11:54 AM Emil Renner Berthing
<emil.renner.berthing@xxxxxxxxxxxxx> wrote:
>
> On Mon, 14 Aug 2023 at 23:00, Prabhakar <prabhakar.csengg@xxxxxxxxx> wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > Introduce support for nonstandard noncoherent systems in the RISC-V
> > architecture. It enables function pointer support to handle cache
> > management in such systems.
> >
> > This patch adds a new configuration option called
> > "RISCV_NONSTANDARD_CACHE_OPS." This option is a boolean flag that
> > depends on "RISCV_DMA_NONCOHERENT" and enables the function pointer
> > support for cache management in nonstandard noncoherent systems.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> > Tested-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx> # tyre-kicking on a d1
> > ---
> > v10 -> v11
> > * Changed data type of size from unsigned long to size_t
> > * Reworded doc for struct riscv_cache_ops
> >
> > v9 -> v10
> > * Added __ro_after_init compiler attribute for noncoherent_cache_ops
> > * Renamed clean -> wback
> > * Renamed inval -> inv
> > * Renamed flush -> wback_inv
> >
> > v8 -> v9
> > * New patch
> > ---
> >  arch/riscv/Kconfig                       |  7 ++++
> >  arch/riscv/include/asm/dma-noncoherent.h | 28 +++++++++++++++
> >  arch/riscv/mm/dma-noncoherent.c          | 43 ++++++++++++++++++++++++
> >  arch/riscv/mm/pmem.c                     | 13 +++++++
> >  4 files changed, 91 insertions(+)
> >  create mode 100644 arch/riscv/include/asm/dma-noncoherent.h
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index f52dd125ac5e..a629d383affb 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -269,6 +269,13 @@ config RISCV_DMA_NONCOHERENT
> >         select ARCH_HAS_SYNC_DMA_FOR_DEVICE
> >         select DMA_DIRECT_REMAP
> >
> > +config RISCV_NONSTANDARD_CACHE_OPS
> > +       bool
> > +       depends on RISCV_DMA_NONCOHERENT
> > +       help
> > +         This enables function pointer support for non-standard noncoherent
> > +         systems to handle cache management.
> > +
> >  config AS_HAS_INSN
> >         def_bool $(as-instr,.insn r 51$(comma) 0$(comma) 0$(comma) t0$(comma) t0$(comma) zero)
> >
> > diff --git a/arch/riscv/include/asm/dma-noncoherent.h b/arch/riscv/include/asm/dma-noncoherent.h
> > new file mode 100644
> > index 000000000000..2fc43f73f766
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/dma-noncoherent.h
> > @@ -0,0 +1,28 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright (C) 2023 Renesas Electronics Corp.
> > + */
> > +
> > +#ifndef __ASM_DMA_NONCOHERENT_H
> > +#define __ASM_DMA_NONCOHERENT_H
> > +
> > +#include <linux/dma-direct.h>
> > +
> > +/*
> > + * struct riscv_nonstd_cache_ops - Structure for non-standard CMO function pointers
>
> It seems you updated the name in this comment..
>
> > + *
> > + * @wback: Function pointer for cache writeback
> > + * @inv: Function pointer for invalidating cache
> > + * @wback_inv: Function pointer for flushing the cache (writeback + invalidating)
> > + */
> > +struct riscv_cache_ops {
>
> ..but not the actual struct. I don't have any opinion on which is the
> best name, but they should probably match.
>
Argh! Thanks for pointing out that I'll fix it and resend the series.

Cheers,
Prabhakar

> > +       void (*wback)(phys_addr_t paddr, size_t size);
> > +       void (*inv)(phys_addr_t paddr, size_t size);
> > +       void (*wback_inv)(phys_addr_t paddr, size_t size);
> > +};
> > +
> > +extern struct riscv_cache_ops noncoherent_cache_ops;
> > +
> > +void riscv_noncoherent_register_cache_ops(const struct riscv_cache_ops *ops);
> > +
> > +#endif /* __ASM_DMA_NONCOHERENT_H */
> > diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
> > index b6a1e9cc9339..853446525a19 100644
> > --- a/arch/riscv/mm/dma-noncoherent.c
> > +++ b/arch/riscv/mm/dma-noncoherent.c
> > @@ -9,13 +9,26 @@
> >  #include <linux/dma-map-ops.h>
> >  #include <linux/mm.h>
> >  #include <asm/cacheflush.h>
> > +#include <asm/dma-noncoherent.h>
> >
> >  static bool noncoherent_supported __ro_after_init;
> >
> > +struct riscv_cache_ops noncoherent_cache_ops __ro_after_init = {
> > +       .wback = NULL,
> > +       .inv = NULL,
> > +       .wback_inv = NULL,
> > +};
> > +
> >  static inline void arch_dma_cache_wback(phys_addr_t paddr, size_t size)
> >  {
> >         void *vaddr = phys_to_virt(paddr);
> >
> > +#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
> > +       if (unlikely(noncoherent_cache_ops.wback)) {
> > +               noncoherent_cache_ops.wback(paddr, size);
> > +               return;
> > +       }
> > +#endif
> >         ALT_CMO_OP(clean, vaddr, size, riscv_cbom_block_size);
> >  }
> >
> > @@ -23,6 +36,13 @@ static inline void arch_dma_cache_inv(phys_addr_t paddr, size_t size)
> >  {
> >         void *vaddr = phys_to_virt(paddr);
> >
> > +#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
> > +       if (unlikely(noncoherent_cache_ops.inv)) {
> > +               noncoherent_cache_ops.inv(paddr, size);
> > +               return;
> > +       }
> > +#endif
> > +
> >         ALT_CMO_OP(inval, vaddr, size, riscv_cbom_block_size);
> >  }
> >
> > @@ -30,6 +50,13 @@ static inline void arch_dma_cache_wback_inv(phys_addr_t paddr, size_t size)
> >  {
> >         void *vaddr = phys_to_virt(paddr);
> >
> > +#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
> > +       if (unlikely(noncoherent_cache_ops.wback_inv)) {
> > +               noncoherent_cache_ops.wback_inv(paddr, size);
> > +               return;
> > +       }
> > +#endif
> > +
> >         ALT_CMO_OP(flush, vaddr, size, riscv_cbom_block_size);
> >  }
> >
> > @@ -49,6 +76,13 @@ void arch_dma_prep_coherent(struct page *page, size_t size)
> >  {
> >         void *flush_addr = page_address(page);
> >
> > +#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
> > +       if (unlikely(noncoherent_cache_ops.wback_inv)) {
> > +               noncoherent_cache_ops.wback_inv(page_to_phys(page), size);
> > +               return;
> > +       }
> > +#endif
> > +
> >         ALT_CMO_OP(flush, flush_addr, size, riscv_cbom_block_size);
> >  }
> >
> > @@ -74,3 +108,12 @@ void riscv_noncoherent_supported(void)
> >              "Non-coherent DMA support enabled without a block size\n");
> >         noncoherent_supported = true;
> >  }
> > +
> > +void riscv_noncoherent_register_cache_ops(const struct riscv_cache_ops *ops)
> > +{
> > +       if (!ops)
> > +               return;
> > +
> > +       noncoherent_cache_ops = *ops;
> > +}
> > +EXPORT_SYMBOL_GPL(riscv_noncoherent_register_cache_ops);
> > diff --git a/arch/riscv/mm/pmem.c b/arch/riscv/mm/pmem.c
> > index 089df92ae876..c5fc5ec96f6d 100644
> > --- a/arch/riscv/mm/pmem.c
> > +++ b/arch/riscv/mm/pmem.c
> > @@ -7,15 +7,28 @@
> >  #include <linux/libnvdimm.h>
> >
> >  #include <asm/cacheflush.h>
> > +#include <asm/dma-noncoherent.h>
> >
> >  void arch_wb_cache_pmem(void *addr, size_t size)
> >  {
> > +#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
> > +       if (unlikely(noncoherent_cache_ops.wback)) {
> > +               noncoherent_cache_ops.wback(virt_to_phys(addr), size);
> > +               return;
> > +       }
> > +#endif
> >         ALT_CMO_OP(clean, addr, size, riscv_cbom_block_size);
> >  }
> >  EXPORT_SYMBOL_GPL(arch_wb_cache_pmem);
> >
> >  void arch_invalidate_pmem(void *addr, size_t size)
> >  {
> > +#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
> > +       if (unlikely(noncoherent_cache_ops.inv)) {
> > +               noncoherent_cache_ops.inv(virt_to_phys(addr), size);
> > +               return;
> > +       }
> > +#endif
> >         ALT_CMO_OP(inval, addr, size, riscv_cbom_block_size);
> >  }
> >  EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
> > --
> > 2.34.1
> >
> >
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