linux-kernel - Re: [PATCH v5 1/9] RISC-V: Add riscv_fw_parent

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Message-ID: <20230711-3151a76400deb88b218e9f9b@orel>
Date:   Tue, 11 Jul 2023 15:26:12 +0200
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Anup Patel <apatel@...tanamicro.com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Atish Patra <atishp@...shpatra.org>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Conor Dooley <conor@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Anup Patel <anup@...infault.org>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v5 1/9] RISC-V: Add riscv_fw_parent_hartid() function

On Mon, Jul 10, 2023 at 03:13:13PM +0530, Anup Patel wrote:
> We add common riscv_fw_parent_hartid() which help device drivers
> to get parent hartid of the INTC (i.e. local interrupt controller)
> fwnode. This should work for both DT and ACPI.
> 
> Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> ---
>  arch/riscv/include/asm/processor.h |  3 +++
>  arch/riscv/kernel/cpu.c            | 16 ++++++++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index c950a8d9edef..39dc23a18f88 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -81,6 +81,9 @@ int riscv_of_processor_hartid(struct device_node *node, unsigned long *hartid);
>  int riscv_early_of_processor_hartid(struct device_node *node, unsigned long *hartid);
>  int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid);
>  
> +struct fwnode_handle;
> +int riscv_fw_parent_hartid(struct fwnode_handle *node, unsigned long *hartid);
> +
>  extern void riscv_fill_hwcap(void);
>  extern int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
>  
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index a2fc952318e9..9be9b3b1f333 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -96,6 +96,22 @@ int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid)
>  	return -1;
>  }
>  
> +/* Find hart ID of the CPU fwnode under which given fwnode falls. */

This comment matches the comment for riscv_of_parent_hartid(), but I don't
think it will be correct for the !is_of_node(node) case since
fwnode_property_read_u64_array() isn't obliged to walk up its tree.
Looking ahead it appears riscv_fw_parent_hartid() is only called with the
parent node, so we could just drop this function and use
fwnode_property_read_u64_array() directly at the two call sites.

Thanks,
drew

> +int riscv_fw_parent_hartid(struct fwnode_handle *node, unsigned long *hartid)
> +{
> +	int rc;
> +	u64 temp;
> +
> +	if (!is_of_node(node)) {
> +		rc = fwnode_property_read_u64_array(node, "hartid", &temp, 1);
> +		if (!rc)
> +			*hartid = temp;
> +	} else
> +		rc = riscv_of_parent_hartid(to_of_node(node), hartid);
> +
> +	return rc;
> +}
> +
>  DEFINE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
>  
>  unsigned long riscv_cached_mvendorid(unsigned int cpu_id)
> -- 
> 2.34.1
>