linux-kernel - Re: [RFC PATCH v3 35/37] kvx: Add IPI driver

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Message-ID: <cbd74fa5-d4ad-4ed0-a680-6ff5e3b8ff84@kernel.org>
Date: Mon, 22 Jul 2024 14:39:20 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: ysionneau@...rayinc.com, linux-kernel@...r.kernel.org,
 Thomas Gleixner <tglx@...utronix.de>
Cc: Jonathan Borne <jborne@...rayinc.com>,
 Julian Vetter <jvetter@...rayinc.com>,
 Clement Leger <clement@...ment-leger.fr>,
 Guillaume Thouvenin <thouveng@...il.com>, Luc Michel <luc@...chel.fr>,
 Jules Maselbas <jmaselbas@...v.net>, bpf@...r.kernel.org
Subject: Re: [RFC PATCH v3 35/37] kvx: Add IPI driver

On 22/07/2024 11:41, ysionneau@...rayinc.com wrote:
> From: Yann Sionneau <ysionneau@...rayinc.com>
> 
> The Inter-Processor Interrupt Controller (IPI) provides a fast
> synchronization mechanism to the software. It exposes eight independent
> sets of registers that can be used to notify each processor in the cluster.
> 
> Co-developed-by: Clement Leger <clement@...ment-leger.fr>
> Signed-off-by: Clement Leger <clement@...ment-leger.fr>
> Co-developed-by: Guillaume Thouvenin <thouveng@...il.com>
> Signed-off-by: Guillaume Thouvenin <thouveng@...il.com>
> Co-developed-by: Julian Vetter <jvetter@...rayinc.com>
> Signed-off-by: Julian Vetter <jvetter@...rayinc.com>
> Co-developed-by: Luc Michel <luc@...chel.fr>
> Signed-off-by: Luc Michel <luc@...chel.fr>
> Signed-off-by: Jules Maselbas <jmaselbas@...v.net>
> Signed-off-by: Yann Sionneau <ysionneau@...rayinc.com>

...

> +
> +int __init kvx_ipi_ctrl_init(struct device_node *node,
> +			     struct device_node *parent)
> +{
> +	int ret;
> +	unsigned int ipi_irq;
> +	void __iomem *ipi_base;
> +
> +	BUG_ON(!node);

Fix your code instead.

> +
> +	ipi_base = of_iomap(node, 0);
> +	BUG_ON(!ipi_base);

No, handle it by returning.

> +
> +	kvx_ipi_controller.regs = ipi_base;
> +
> +	/* Init mask for interrupts to PE0 -> PE15 */
> +	writel(KVX_IPI_CPU_MASK, kvx_ipi_controller.regs + IPI_MASK_OFFSET);
> +
> +	ipi_irq = irq_of_parse_and_map(node, 0);
> +	if (!ipi_irq) {
> +		pr_err("Failed to parse irq: %d\n", ipi_irq);
> +		return -EINVAL;
> +	}
> +
> +	ret = request_percpu_irq(ipi_irq, ipi_irq_handler,
> +						"kvx_ipi", &kvx_ipi_controller);
> +	if (ret) {
> +		pr_err("can't register interrupt %d (%d)\n",
> +						ipi_irq, ret);
> +		return ret;
> +	}
> +	kvx_ipi_controller.ipi_irq = ipi_irq;
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_IRQ_KVX_STARTING,
> +				"kvx/ipi:online",
> +				kvx_ipi_starting_cpu,
> +				kvx_ipi_dying_cpu);
> +	if (ret < 0) {
> +		pr_err("Failed to setup hotplug state");
> +		return ret;
> +	}
> +
> +	set_smp_cross_call(kvx_ipi_send);
> +	pr_info("controller probed\n");

Drop this simple probe successes. This is not the way to trace system
bootup. Keep only reasonable amount, not every driver printing that its
initcall started.

Best regards,
Krzysztof