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

Sunil V L
2023-02-24T12:03:33Z

On Mon, Feb 20, 2023 at 05:36:48PM +0100, Andrew Jones wrote:
> 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.
>
Sure. Will update.

> > + }
> > +
> > + 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.
>
Okay.

> > + */
> > +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?
>
Yes, we can use BUG_ON. Will update.

> > + }
> > +
> > + 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'.
>
Okay.
> > + 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!
Sunil