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

Message ID	20230216182043.1946553-9-sunilvl@ventanamicro.com (mailing list archive)
State	Superseded
Headers	show Return-Path: <linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org> From: Sunil V L <sunilvl@ventanamicro.com> To: Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Paul Walmsley <paul.walmsley@sifive.com>, "Rafael J . Wysocki" <rafael@kernel.org>, Len Brown <lenb@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Marc Zyngier <maz@kernel.org>, Jonathan Corbet <corbet@lwn.net> Subject: [PATCH V2 08/21] drivers/acpi: RISC-V: Add RHCT related code Date: Thu, 16 Feb 2023 23:50:30 +0530 Message-Id: <20230216182043.1946553-9-sunilvl@ventanamicro.com> In-Reply-To: <20230216182043.1946553-1-sunilvl@ventanamicro.com> References: <20230216182043.1946553-1-sunilvl@ventanamicro.com> MIME-Version: 1.0 Precedence: list Cc: Anup Patel <apatel@ventanamicro.com>, linux-doc@vger.kernel.org, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Atish Patra <atishp@rivosinc.com>, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, Conor Dooley <conor.dooley@microchip.com>, linux-riscv@lists.infradead.org, Andrew Jones <ajones@ventanamicro.com> Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" <linux-riscv-bounces@lists.infradead.org> Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org
Series	Add basic ACPI support for RISC-V \| expand [V2,00/21] Add basic ACPI support for RISC-V [V2,01/21] riscv: move sbi_init() earlier before jump_label_init() [V2,02/21] ACPICA: MADT: Add RISC-V INTC interrupt controller [V2,03/21] ACPICA: Add structure definitions for RISC-V RHCT [V2,04/21] RISC-V: Add support to build the ACPI core [V2,05/21] ACPI: Kconfig: Enable ACPI_PROCESSOR for RISC-V [V2,06/21] ACPI: OSL: Make should_use_kmap() 0 for RISC-V. [V2,07/21] ACPI: processor_core: RISC-V: Enable mapping processor to the hartid [V2,08/21] drivers/acpi: RISC-V: Add RHCT related code [V2,09/21] RISC-V: smpboot: Create wrapper smp_setup() [V2,10/21] RISC-V: smpboot: Add ACPI support in smp_setup() [V2,11/21] RISC-V: ACPI: Add a function to retrieve the hartid [V2,12/21] RISC-V: cpufeature: Add ACPI support in riscv_fill_hwcap() [V2,13/21] RISC-V: cpu: Enable cpuinfo for ACPI systems [V2,14/21] irqchip/riscv-intc: Add ACPI support [V2,15/21] clocksource/timer-riscv: Refactor riscv_timer_init_dt() [V2,16/21] clocksource/timer-riscv: Add ACPI support [V2,17/21] RISC-V: time.c: Add ACPI support for time_init() [V2,18/21] RISC-V: Add ACPI initialization in setup_arch() [V2,19/21] RISC-V: Enable ACPI in defconfig [V2,20/21] MAINTAINERS: Add entry for drivers/acpi/riscv [V2,21/21] Documentation/kernel-parameters.txt: Add RISC-V for ACPI parameter

Message ID

20230216182043.1946553-9-sunilvl@ventanamicro.com (mailing list archive)

State

Superseded

Headers

From: Sunil V L <sunilvl@ventanamicro.com>
To: Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Len Brown <lenb@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Marc Zyngier <maz@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>
Subject: [PATCH V2 08/21] drivers/acpi: RISC-V: Add RHCT related code
Date: Thu, 16 Feb 2023 23:50:30 +0530
Message-Id: <20230216182043.1946553-9-sunilvl@ventanamicro.com>
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Cc: Anup Patel <apatel@ventanamicro.com>, linux-doc@vger.kernel.org,
 "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
 Atish Patra <atishp@rivosinc.com>, linux-kernel@vger.kernel.org,
 linux-acpi@vger.kernel.org, Conor Dooley <conor.dooley@microchip.com>,
 linux-riscv@lists.infradead.org, Andrew Jones <ajones@ventanamicro.com>
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Series

Add basic ACPI support for RISC-V | expand

Context	Check	Description
conchuod/tree_selection	fail	Failed to apply to next/pending-fixes or riscv/for-next

Context

Check

Description

conchuod/tree_selection

fail

Failed to apply to next/pending-fixes or riscv/for-next

Commit Message

Sunil V L Feb. 16, 2023, 6:20 p.m. UTC

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

Comments

Andrew Jones Feb. 20, 2023, 4:36 p.m. UTC | #1

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

Sunil V L Feb. 24, 2023, 12:03 p.m. UTC | #2

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

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();
+	}
+
+	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
+ */
+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;
+	}
+
+	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;
+		switch (node->type) {
+		case 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;
+			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;
+}

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

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