Re: [PATCH V2 08/21] drivers/acpi: RISC-V: Add RHCT related code

Andrew Jones
2023-02-20T16:36:57Z

On Thu, Feb 16, 2023 at 11:50:30PM +0530, Sunil V L 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>
> ---
> arch/riscv/include/asm/acpi.h | 9 ++++
> drivers/acpi/Makefile | 2 +
> drivers/acpi/riscv/Makefile | 2 +
> drivers/acpi/riscv/rhct.c | 92 +++++++++++++++++++++++++++++++++++
> 4 files changed, 105 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 4a3622b38159..7bc49f65c86b 100644
> --- a/arch/riscv/include/asm/acpi.h
> +++ b/arch/riscv/include/asm/acpi.h
> @@ -58,6 +58,15 @@ static inline bool acpi_has_cpu_in_madt(void)
>
> static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>
> +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..5bafc236d627
> --- /dev/null
> +++ b/drivers/acpi/riscv/rhct.c
> @@ -0,0 +1,92 @@
> +// 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 void acpi_rhct_warn_missing(void)
> +{
> + pr_warn_once("No RHCT table found\n");
> +}
> +
> +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))
> + acpi_rhct_warn_missing();

Probably don't need the wrapper function for this one callsite. Also,
returning NULL here, rather than relying on acpi_get_table() to set
rhct to NULL would be a bit more robust.

> + }
> +
> + 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, pass NULL so that the table remains in memory

...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 acpi_cpu_id, const char **isa)
> +{
> + struct acpi_rhct_node_header *node, *ref_node, *end;
> + struct acpi_table_rhct *rhct;
> + struct acpi_rhct_hart_info *hart_info;
> + struct acpi_rhct_isa_string *isa_node;
> + u32 *hart_info_node_offset;
> + int i, j;
> + u32 size_hdr = sizeof(struct acpi_rhct_node_header);
> + u32 size_hartinfo = sizeof(struct acpi_rhct_hart_info);
> +
> + if (acpi_disabled) {
> + pr_debug("%s: acpi is disabled\n", __func__);
> + return -1;

This seems like something that should never happen and easy to catch
and fix with a BUG_ON. Is there any chance that BUG'ing here would
be a bad idea?

> + }
> +
> + if (!table) {
> + rhct = (struct acpi_table_rhct *)acpi_get_rhct();
> + if (!rhct)
> + return -ENOENT;
> + } else {
> + rhct = (struct acpi_table_rhct *)table;
> + }
> +
> + node = ACPI_ADD_PTR(struct acpi_rhct_node_header, rhct, rhct->node_offset);
> + end = ACPI_ADD_PTR(struct acpi_rhct_node_header, rhct, rhct->header.length);
> +
> + for (i = 0; i < rhct->node_count; i++) {
> + if (node >= end)
> + break;

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))

> + switch (node->type) {
> + case ACPI_RHCT_NODE_TYPE_HART_INFO:

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)
> + break;

With the above suggested changes, this 'break' becomes 'continue'.

> + for (j = 0; j < hart_info->num_offsets; j++) {
> + ref_node = ACPI_ADD_PTR(struct acpi_rhct_node_header,
> + rhct, hart_info_node_offset[j]);
> + 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;
> + }
> + }
> + break;
> + }
> + node = ACPI_ADD_PTR(struct acpi_rhct_node_header, node, node->length);
> + }
> +
> + return -1;
> +}
> --
> 2.34.1
>

Other than the nits,

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>

Thanks,
drew