Date:   Fri, 24 Feb 2023 17:33:15 +0530
From:   Sunil V L <sunilvl@ventanamicro.com>
To:     Andrew Jones <ajones@ventanamicro.com>
Cc:     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>,
        linux-riscv@lists.infradead.org, linux-acpi@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        Conor Dooley <conor.dooley@microchip.com>,
        Anup Patel <apatel@ventanamicro.com>,
        Atish Patra <atishp@rivosinc.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Subject: Re: [PATCH V2 08/21] drivers/acpi: RISC-V: Add RHCT related code
Message-ID: <Y/ingw3nYwO7PUHm@sunil-laptop>
References: <20230216182043.1946553-1-sunilvl@ventanamicro.com>
 <20230216182043.1946553-9-sunilvl@ventanamicro.com>
 <20230220163648.72bw7ujwzkx42far@orel>
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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