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Date:   Wed, 26 Apr 2023 11:45:02 -0700 (PDT)
Subject:     Re: [PATCH V4 09/23] drivers/acpi: RISC-V: Add RHCT related code
In-Reply-To: <20230404182037.863533-10-sunilvl@ventanamicro.com>
CC:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
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        rafael@kernel.org, davem@davemloft.net, sunilvl@ventanamicro.com,
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From:   Palmer Dabbelt <palmer@dabbelt.com>
To:     sunilvl@ventanamicro.com
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On Tue, 04 Apr 2023 11:20:23 PDT (-0700), sunilvl@ventanamicro.com wrote:
> RHCT is a new table defined for RISC-V to communicate the
> features of the CPU to the OS. Create a new architecture folder
> in drivers/acpi and add RHCT parsing code.
>
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> ---
>  arch/riscv/include/asm/acpi.h |  9 ++++
>  drivers/acpi/Makefile         |  2 +
>  drivers/acpi/riscv/Makefile   |  2 +
>  drivers/acpi/riscv/rhct.c     | 83 +++++++++++++++++++++++++++++++++++
>  4 files changed, 96 insertions(+)
>  create mode 100644 drivers/acpi/riscv/Makefile
>  create mode 100644 drivers/acpi/riscv/rhct.c
>
> diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
> index 1606dce8992e..2b3e78d5a13b 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -61,6 +61,15 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>
>  struct acpi_madt_rintc *acpi_cpu_get_madt_rintc(int cpu);
>  u32 get_acpi_id_for_cpu(int cpu);
> +int acpi_get_riscv_isa(struct acpi_table_header *table,
> +		       unsigned int cpu, const char **isa);
> +#else
> +static inline int acpi_get_riscv_isa(struct acpi_table_header *table,
> +				     unsigned int cpu, const char **isa)
> +{
> +	return -EINVAL;
> +}
> +
>  #endif /* CONFIG_ACPI */
>
>  #endif /*_ASM_ACPI_H*/
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index feb36c0b9446..3fc5a0d54f6e 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -131,3 +131,5 @@ obj-y				+= dptf/
>  obj-$(CONFIG_ARM64)		+= arm64/
>
>  obj-$(CONFIG_ACPI_VIOT)		+= viot.o
> +
> +obj-$(CONFIG_RISCV)		+= riscv/
> diff --git a/drivers/acpi/riscv/Makefile b/drivers/acpi/riscv/Makefile
> new file mode 100644
> index 000000000000..8b3b126e0b94
> --- /dev/null
> +++ b/drivers/acpi/riscv/Makefile
> @@ -0,0 +1,2 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-y 	+= rhct.o
> diff --git a/drivers/acpi/riscv/rhct.c b/drivers/acpi/riscv/rhct.c
> new file mode 100644
> index 000000000000..ea78d906a0fe
> --- /dev/null
> +++ b/drivers/acpi/riscv/rhct.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2022-2023, Ventana Micro Systems Inc
> + *	Author: Sunil V L <sunilvl@ventanamicro.com>
> + *
> + */
> +
> +#define pr_fmt(fmt)	"ACPI: RHCT: " fmt
> +
> +#include <linux/acpi.h>
> +
> +static struct acpi_table_header *acpi_get_rhct(void)
> +{
> +	static struct acpi_table_header *rhct;
> +	acpi_status status;
> +
> +	/*
> +	 * RHCT will be used at runtime on every CPU, so we
> +	 * don't need to call acpi_put_table() to release the table mapping.
> +	 */
> +	if (!rhct) {
> +		status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
> +		if (ACPI_FAILURE(status)) {
> +			pr_warn_once("No RHCT table found\n");
> +			return NULL;
> +		}
> +	}
> +
> +	return rhct;
> +}
> +
> +/*
> + * During early boot, the caller should call acpi_get_table() and pass its pointer to
> + * these functions(and free up later). At run time, since this table can be used
> + * multiple times, NULL may be passed in order to use the cached table.
> + */
> +int acpi_get_riscv_isa(struct acpi_table_header *table, unsigned int cpu, const char **isa)
> +{
> +	struct acpi_rhct_node_header *node, *ref_node, *end;
> +	u32 size_hdr = sizeof(struct acpi_rhct_node_header);
> +	u32 size_hartinfo = sizeof(struct acpi_rhct_hart_info);
> +	struct acpi_rhct_hart_info *hart_info;
> +	struct acpi_rhct_isa_string *isa_node;
> +	struct acpi_table_rhct *rhct;
> +	u32 *hart_info_node_offset;
> +	u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> +
> +	BUG_ON(acpi_disabled);
> +
> +	if (!table) {
> +		rhct = (struct acpi_table_rhct *)acpi_get_rhct();
> +		if (!rhct)
> +			return -ENOENT;
> +	} else {
> +		rhct = (struct acpi_table_rhct *)table;
> +	}
> +
> +	end = ACPI_ADD_PTR(struct acpi_rhct_node_header, rhct, rhct->header.length);
> +
> +	for (node = ACPI_ADD_PTR(struct acpi_rhct_node_header, rhct, rhct->node_offset);
> +	     node < end;
> +	     node = ACPI_ADD_PTR(struct acpi_rhct_node_header, node, node->length)) {
> +		if (node->type == ACPI_RHCT_NODE_TYPE_HART_INFO) {
> +			hart_info = ACPI_ADD_PTR(struct acpi_rhct_hart_info, node, size_hdr);
> +			hart_info_node_offset = ACPI_ADD_PTR(u32, hart_info, size_hartinfo);
> +			if (acpi_cpu_id != hart_info->uid)
> +				continue;
> +
> +			for (int i = 0; i < hart_info->num_offsets; i++) {
> +				ref_node = ACPI_ADD_PTR(struct acpi_rhct_node_header,
> +							rhct, hart_info_node_offset[i]);
> +				if (ref_node->type == ACPI_RHCT_NODE_TYPE_ISA_STRING) {
> +					isa_node = ACPI_ADD_PTR(struct acpi_rhct_isa_string,
> +								ref_node, size_hdr);
> +					*isa = isa_node->isa;
> +					return 0;
> +				}
> +			}
> +		}
> +	}
> +
> +	return -1;
> +}

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>