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Date:   Wed, 2 Aug 2023 20:09:18 +0300
From:   Andrew Jones <ajones@ventanamicro.com>
To:     Anup Patel <apatel@ventanamicro.com>
Cc:     Palmer Dabbelt <palmer@dabbelt.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Marc Zyngier <maz@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Conor Dooley <conor+dt@kernel.org>,
        Atish Patra <atishp@atishpatra.org>,
        Sunil V L <sunilvl@ventanamicro.com>,
        Saravana Kannan <saravanak@google.com>,
        Anup Patel <anup@brainfault.org>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH v7 01/15] RISC-V: Add riscv_get_intc_hartid() function
Message-ID: <20230802-b0c478839e55890385d98f31@orel>
References: <20230802150018.327079-1-apatel@ventanamicro.com>
 <20230802150018.327079-2-apatel@ventanamicro.com>
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On Wed, Aug 02, 2023 at 08:30:04PM +0530, Anup Patel wrote:
> We add a common riscv_get_intc_hartid() which help device drivers to
> get hartid of the HART associated with a INTC (i.e. local interrupt
> controller) fwnode. This new function is more generic compared to
> the existing riscv_of_parent_hartid() function hence we also replace
> use of riscv_of_parent_hartid() with riscv_get_intc_hartid().
> 
> Also, while we are here let us update riscv_of_parent_hartid() to
> always return the hartid irrespective whether the CPU/HART DT node
> is disabled or not.

This change should probably be a separate patch with its own
justification in its commit message.

> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
>  arch/riscv/include/asm/processor.h |  4 +++-
>  arch/riscv/kernel/cpu.c            | 26 ++++++++++++++++++++------
>  drivers/irqchip/irq-riscv-intc.c   |  2 +-
>  drivers/irqchip/irq-sifive-plic.c  |  3 ++-
>  4 files changed, 26 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
> index c950a8d9edef..662da1e112dd 100644
> --- a/arch/riscv/include/asm/processor.h
> +++ b/arch/riscv/include/asm/processor.h
> @@ -79,7 +79,9 @@ static inline void wait_for_interrupt(void)
>  struct device_node;
>  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_get_intc_hartid(struct fwnode_handle *node, unsigned long *hartid);

Do we want a function that is named in a way that appears to be
intc-specific in processor.h?

>  
>  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..c3eaa8a55bbe 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -81,21 +81,35 @@ int riscv_early_of_processor_hartid(struct device_node *node, unsigned long *har
>   * To achieve this, we walk up the DT tree until we find an active
>   * RISC-V core (HART) node and extract the cpuid from it.
>   */
> -int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid)
> +static int riscv_of_parent_hartid(struct device_node *node,
> +				  unsigned long *hartid)
>  {
> -	int rc;
> -
>  	for (; node; node = node->parent) {
>  		if (of_device_is_compatible(node, "riscv")) {
> -			rc = riscv_of_processor_hartid(node, hartid);
> -			if (!rc)
> -				return 0;
> +			*hartid = (unsigned long)of_get_cpu_hwid(node, 0);

Shouldn't we still do something like

   if (*hartid == ~0UL) {
       pr_warn_once("Found CPU without hart ID\n");
       return -ENODEV;
   }

> +			return 0;
>  		}
>  	}
>  
>  	return -1;
>  }
>  
> +/* Find hart ID of the INTC fwnode. */
> +int riscv_get_intc_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);

This fwnode property read call seems premature, since we don't have any
way to know that "hartid" will be a property of the intc since it's not a
property documented in the DT binding. (I know Sunil has a series in
progress which will introduce "hartid" for ACPI, but, even then, it seems
like we need some documentation to point at that says '"hartid" is the
name to use'.

> +		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)
> diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
> index 4adeee1bc391..65f4a2afb381 100644
> --- a/drivers/irqchip/irq-riscv-intc.c
> +++ b/drivers/irqchip/irq-riscv-intc.c
> @@ -143,7 +143,7 @@ static int __init riscv_intc_init(struct device_node *node,
>  	int rc;
>  	unsigned long hartid;
>  
> -	rc = riscv_of_parent_hartid(node, &hartid);
> +	rc = riscv_get_intc_hartid(of_fwnode_handle(node), &hartid);
>  	if (rc < 0) {
>  		pr_warn("unable to find hart id for %pOF\n", node);
>  		return 0;
> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> index e1484905b7bd..56b0544b1f27 100644
> --- a/drivers/irqchip/irq-sifive-plic.c
> +++ b/drivers/irqchip/irq-sifive-plic.c
> @@ -477,7 +477,8 @@ static int __init __plic_init(struct device_node *node,
>  			continue;
>  		}
>  
> -		error = riscv_of_parent_hartid(parent.np, &hartid);
> +		error = riscv_get_intc_hartid(of_fwnode_handle(parent.np),
> +					      &hartid);
>  		if (error < 0) {
>  			pr_warn("failed to parse hart ID for context %d.\n", i);
>  			continue;
> -- 
> 2.34.1
>

Thanks,
drew