Re: [PATCH v2 2/3] riscv: Implement Zicbom-based cache management operations

Guo Ren
2022-05-13T13:50:00Z

Reviewed-by: Guo Ren <guoren@kernel.org>

On Thu, May 12, 2022 at 12:19 PM Anup Patel <anup@brainfault.org> wrote:
>
> On Thu, May 12, 2022 at 3:11 AM Heiko Stuebner <heiko@sntech.de> wrote:
> >
> > The Zicbom ISA-extension was ratified in november 2021
> > and introduces instructions for dcache invalidate, clean
> > and flush operations.
> >
> > Implement cache management operations based on them.
> >
> > Of course not all cores will support this, so implement an
> > alternative-based mechanism that replaces empty instructions
> > with ones done around Zicbom instructions.
> >
> > We're using prebuild instructions for the Zicbom instructions
> > for now, to not require a bleeding-edge compiler (gcc-12)
> > for these somewhat simple instructions.
> >
> > Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Atish Patra <atish.patra@wdc.com>
> > Cc: Guo Ren <guoren@kernel.org>
>
> Looks good to me.
>
> Reviewed-by: Anup Patel <anup@brainfault.org>
>
> Regards,
> Anup
>
> > ---
> > arch/riscv/Kconfig | 15 +++++
> > arch/riscv/include/asm/cacheflush.h | 6 ++
> > arch/riscv/include/asm/errata_list.h | 39 +++++++++++-
> > arch/riscv/include/asm/hwcap.h | 1 +
> > arch/riscv/kernel/cpu.c | 1 +
> > arch/riscv/kernel/cpufeature.c | 17 +++++
> > arch/riscv/kernel/setup.c | 2 +
> > arch/riscv/mm/Makefile | 1 +
> > arch/riscv/mm/dma-noncoherent.c | 92 ++++++++++++++++++++++++++++
> > 9 files changed, 173 insertions(+), 1 deletion(-)
> > create mode 100644 arch/riscv/mm/dma-noncoherent.c
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 65285b980134..532db45367a7 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -363,6 +363,21 @@ config RISCV_ISA_SVPBMT
> >
> > If you don't know what to do here, say Y.
> >
> > +config RISCV_ISA_ZICBOM
> > + bool "Zicbom extension support for non-coherent dma operation"
> > + select ARCH_HAS_DMA_PREP_COHERENT
> > + select ARCH_HAS_SYNC_DMA_FOR_DEVICE
> > + select ARCH_HAS_SYNC_DMA_FOR_CPU
> > + select ARCH_HAS_SETUP_DMA_OPS
> > + select DMA_DIRECT_REMAP
> > + select RISCV_ALTERNATIVE
> > + default y
> > + help
> > + Adds support to dynamically detect the presence of the ZICBOM extension
> > + (Cache Block Management Operations) and enable its usage.
> > +
> > + If you don't know what to do here, say Y.
> > +
> > config FPU
> > bool "FPU support"
> > default y
> > diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
> > index 23ff70350992..eb12d014b158 100644
> > --- a/arch/riscv/include/asm/cacheflush.h
> > +++ b/arch/riscv/include/asm/cacheflush.h
> > @@ -42,6 +42,12 @@ void flush_icache_mm(struct mm_struct *mm, bool local);
> >
> > #endif /* CONFIG_SMP */
> >
> > +#ifdef CONFIG_RISCV_ISA_ZICBOM
> > +void riscv_init_cbom_blocksize(void);
> > +#else
> > +static inline void riscv_init_cbom_blocksize(void) { }
> > +#endif
> > +
> > /*
> > * Bits in sys_riscv_flush_icache()'s flags argument.
> > */
> > diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> > index 9e2888dbb5b1..eebcd4415049 100644
> > --- a/arch/riscv/include/asm/errata_list.h
> > +++ b/arch/riscv/include/asm/errata_list.h
> > @@ -20,7 +20,8 @@
> > #endif
> >
> > #define CPUFEATURE_SVPBMT 0
> > -#define CPUFEATURE_NUMBER 1
> > +#define CPUFEATURE_CMO 1
> > +#define CPUFEATURE_NUMBER 2
> >
> > #ifdef __ASSEMBLY__
> >
> > @@ -93,6 +94,42 @@ asm volatile(ALTERNATIVE( \
> > #define ALT_THEAD_PMA(_val)
> > #endif
> >
> > +/*
> > + * cbo.clean rs1
> > + * | 31 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> > + * 0...01 rs1 010 00000 0001111
> > + *
> > + * cbo.flush rs1
> > + * | 31 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> > + * 0...10 rs1 010 00000 0001111
> > + *
> > + * cbo.inval rs1
> > + * | 31 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
> > + * 0...00 rs1 010 00000 0001111
> > + */
> > +#define CBO_INVAL_A0 ".long 0x15200F"
> > +#define CBO_CLEAN_A0 ".long 0x25200F"
> > +#define CBO_FLUSH_A0 ".long 0x05200F"
> > +
> > +#define ALT_CMO_OP(_op, _start, _size, _cachesize) \
> > +asm volatile(ALTERNATIVE( \
> > + "nop\n\t" \
> > + "nop\n\t" \
> > + "nop\n\t" \
> > + "nop\n\t" \
> > + "nop", \
> > + "mv a0, %1\n\t" \
> > + "j 2f\n\t" \
> > + "3:\n\t" \
> > + CBO_##_op##_A0 "\n\t" \
> > + "add a0, a0, %0\n\t" \
> > + "2:\n\t" \
> > + "bltu a0, %2, 3b\n\t", 0, \
> > + CPUFEATURE_CMO, CONFIG_RISCV_ISA_ZICBOM) \
> > + : : "r"(_cachesize), \
> > + "r"(ALIGN((_start), (_cachesize))), \
> > + "r"(ALIGN((_start) + (_size), (_cachesize))))
> > +
> > #endif /* __ASSEMBLY__ */
> >
> > #endif
> > diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> > index 4e2486881840..6044e402003d 100644
> > --- a/arch/riscv/include/asm/hwcap.h
> > +++ b/arch/riscv/include/asm/hwcap.h
> > @@ -53,6 +53,7 @@ extern unsigned long elf_hwcap;
> > enum riscv_isa_ext_id {
> > RISCV_ISA_EXT_SSCOFPMF = RISCV_ISA_EXT_BASE,
> > RISCV_ISA_EXT_SVPBMT,
> > + RISCV_ISA_EXT_ZICBOM,
> > RISCV_ISA_EXT_ID_MAX = RISCV_ISA_EXT_MAX,
> > };
> >
> > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> > index 40c8776aec12..8f6fc15baa8e 100644
> > --- a/arch/riscv/kernel/cpu.c
> > +++ b/arch/riscv/kernel/cpu.c
> > @@ -89,6 +89,7 @@ int riscv_of_parent_hartid(struct device_node *node)
> > static struct riscv_isa_ext_data isa_ext_arr[] = {
> > __RISCV_ISA_EXT_DATA(sscofpmf, RISCV_ISA_EXT_SSCOFPMF),
> > __RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
> > + __RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
> > __RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
> > };
> >
> > diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> > index dea3ea19deee..db3c02409a4a 100644
> > --- a/arch/riscv/kernel/cpufeature.c
> > +++ b/arch/riscv/kernel/cpufeature.c
> > @@ -199,6 +199,7 @@ void __init riscv_fill_hwcap(void)
> > } else {
> > SET_ISA_EXT_MAP("sscofpmf", RISCV_ISA_EXT_SSCOFPMF);
> > SET_ISA_EXT_MAP("svpbmt", RISCV_ISA_EXT_SVPBMT);
> > + SET_ISA_EXT_MAP("zicbom", RISCV_ISA_EXT_ZICBOM);
> > }
> > #undef SET_ISA_EXT_MAP
> > }
> > @@ -265,12 +266,28 @@ static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage)
> > return false;
> > }
> >
> > +static bool __init_or_module cpufeature_cmo_check_func(unsigned int stage)
> > +{
> > + switch (stage) {
> > + case RISCV_ALTERNATIVES_EARLY_BOOT:
> > + return false;
> > + default:
> > + return riscv_isa_extension_available(NULL, ZICBOM);
> > + }
> > +
> > + return false;
> > +}
> > +
> > static const struct cpufeature_info __initdata_or_module
> > cpufeature_list[CPUFEATURE_NUMBER] = {
> > {
> > .name = "svpbmt",
> > .check_func = cpufeature_svpbmt_check_func
> > },
> > + {
> > + .name = "cmo",
> > + .check_func = cpufeature_cmo_check_func
> > + },
> > };
> >
> > static u32 __init_or_module cpufeature_probe(unsigned int stage)
> > diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> > index 9162e9a824d2..cc5bfeba499a 100644
> > --- a/arch/riscv/kernel/setup.c
> > +++ b/arch/riscv/kernel/setup.c
> > @@ -22,6 +22,7 @@
> > #include <linux/crash_dump.h>
> >
> > #include <asm/alternative.h>
> > +#include <asm/cacheflush.h>
> > #include <asm/cpu_ops.h>
> > #include <asm/early_ioremap.h>
> > #include <asm/pgtable.h>
> > @@ -296,6 +297,7 @@ void __init setup_arch(char **cmdline_p)
> > #endif
> >
> > riscv_fill_hwcap();
> > + riscv_init_cbom_blocksize();
> > apply_boot_alternatives();
> > }
> >
> > diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> > index ac7a25298a04..548f2f3c00e9 100644
> > --- a/arch/riscv/mm/Makefile
> > +++ b/arch/riscv/mm/Makefile
> > @@ -30,3 +30,4 @@ endif
> > endif
> >
> > obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
> > +obj-$(CONFIG_RISCV_ISA_ZICBOM) += dma-noncoherent.o
> > diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
> > new file mode 100644
> > index 000000000000..99decaa25324
> > --- /dev/null
> > +++ b/arch/riscv/mm/dma-noncoherent.c
> > @@ -0,0 +1,92 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * RISC-V specific functions to support DMA for non-coherent devices
> > + *
> > + * Copyright (c) 2021 Western Digital Corporation or its affiliates.
> > + */
> > +
> > +#include <linux/dma-direct.h>
> > +#include <linux/dma-map-ops.h>
> > +#include <linux/init.h>
> > +#include <linux/io.h>
> > +#include <linux/libfdt.h>
> > +#include <linux/mm.h>
> > +#include <linux/of.h>
> > +#include <linux/of_device.h>
> > +
> > +static unsigned int riscv_cbom_block_size = L1_CACHE_BYTES;
> > +
> > +void arch_sync_dma_for_device(phys_addr_t paddr, size_t size, enum dma_data_direction dir)
> > +{
> > + switch (dir) {
> > + case DMA_TO_DEVICE:
> > + ALT_CMO_OP(CLEAN, (unsigned long)phys_to_virt(paddr), size, riscv_cbom_block_size);
> > + break;
> > + case DMA_FROM_DEVICE:
> > + ALT_CMO_OP(INVAL, (unsigned long)phys_to_virt(paddr), size, riscv_cbom_block_size);
> > + break;
> > + case DMA_BIDIRECTIONAL:
> > + ALT_CMO_OP(FLUSH, (unsigned long)phys_to_virt(paddr), size, riscv_cbom_block_size);
> > + break;
> > + default:
> > + break;
> > + }
> > +}
> > +
> > +void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size, enum dma_data_direction dir)
> > +{
> > + switch (dir) {
> > + case DMA_TO_DEVICE:
> > + break;
> > + case DMA_FROM_DEVICE:
> > + case DMA_BIDIRECTIONAL:
> > + ALT_CMO_OP(INVAL, (unsigned long)phys_to_virt(paddr), size, riscv_cbom_block_size);
> > + break;
> > + default:
> > + break;
> > + }
> > +}
> > +
> > +void arch_dma_prep_coherent(struct page *page, size_t size)
> > +{
> > + void *flush_addr = page_address(page);
> > +
> > + memset(flush_addr, 0, size);
> > + ALT_CMO_OP(FLUSH, (unsigned long)flush_addr, size, riscv_cbom_block_size);
> > +}
> > +
> > +void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> > + const struct iommu_ops *iommu, bool coherent)
> > +{
> > + /* If a specific device is dma-coherent, set it here */
> > + dev->dma_coherent = coherent;
> > +}
> > +
> > +void riscv_init_cbom_blocksize(void)
> > +{
> > + struct device_node *node;
> > + int ret;
> > + u32 val;
> > +
> > + for_each_of_cpu_node(node) {
> > + int hartid = riscv_of_processor_hartid(node);
> > + int cbom_hartid;
> > +
> > + if (hartid < 0)
> > + continue;
> > +
> > + /* set block-size for cbom extension if available */
> > + ret = of_property_read_u32(node, "riscv,cbom-block-size", &val);
> > + if (ret)
> > + continue;
> > +
> > + if (!riscv_cbom_block_size) {
> > + riscv_cbom_block_size = val;
> > + cbom_hartid = hartid;
> > + } else {
> > + if (riscv_cbom_block_size != val)
> > + pr_warn("cbom-block-size mismatched between harts %d and %d\n",
> > + cbom_hartid, hartid);
> > + }
> > + }
> > +}
> > --
> > 2.35.1
> >

--
Best Regards
Guo Ren

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