Date:   Wed, 11 May 2022 08:47:50 +0200
From:   Jiri Slaby <jirislaby@...nel.org>
To:     Hitomi Hasegawa <hasegawa-hitomi@...itsu.com>,
        linux-arm-kernel@...ts.infradead.org, soc@...nel.org,
        linux-serial@...r.kernel.org, sumit.garg@...aro.org
Cc:     arnd@...db.de, olof@...om.net, catalin.marinas@....com,
        will@...nel.org, gregkh@...uxfoundation.org,
        jason.wessel@...driver.com, daniel.thompson@...aro.org,
        dianders@...omium.org, linux-kernel@...r.kernel.org,
        kgdb-bugreport@...ts.sourceforge.net, peterz@...radead.org
Subject: Re: [PATCH v4 1/1] soc: fujitsu: Add A64FX diagnostic interrupt
 driver

On 11. 05. 22, 8:21, Hitomi Hasegawa wrote:
> Enable diagnostic interrupts for the Fujitsu A64FX.
> 
> Register the NMI/IRQ corresponding to the A64FX's device definition
> dedicated to diagnostic interrupts, so that when this interrupt is
> sent using the BMC, it causes a panic. This can be used to obtain
> a kernel dump.
> 
> Signed-off-by: Hitomi Hasegawa <hasegawa-hitomi@...itsu.com>

Hi,

I'm not sure why you cc linux-serial, but anyway, comments below :).

> --- /dev/null
> +++ b/drivers/soc/fujitsu/a64fx-diag.c
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * A64FX diag driver.
> + * Copyright (c) 2022 Fujitsu Ltd.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#define A64FX_DIAG_IRQ 1
> +#define BMC_DIAG_INTERRUPT_STATUS_OFFSET (0x0044)
> +#define BMC_DIAG_INTERRUPT_ENABLE_OFFSET (0x0040)
> +#define BMC_DIAG_INTERRUPT_MASK BIT(31)
> +
> +struct a64fx_diag_priv {
> +	int irq;
> +	void __iomem *mmsc_reg_base;
> +	bool has_nmi;

There are unnecessary holes in the struct. If you reorder it, you drop 
some alignment. Like: pointer, int, bool.

> +};
> +
> +static irqreturn_t a64fx_diag_handler_nmi(int irq, void *dev_id)
> +{
> +	nmi_panic(NULL, "a64fx_diag: interrupt received\n");
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static irqreturn_t a64fx_diag_handler_irq(int irq, void *dev_id)
> +{
> +	panic("a64fx_diag: interrupt received\n");
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void a64fx_diag_interrupt_clear(struct a64fx_diag_priv *priv)
> +{
> +	u32 mmsc;
> +	void __iomem *diag_status_reg_addr;

I'm not sure what soc/ maintainers prefer, but inverted xmas tree would 
look/read better.

> +
> +	diag_status_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_STATUS_OFFSET;
> +	mmsc = readl(diag_status_reg_addr);
> +	if (mmsc & BMC_DIAG_INTERRUPT_MASK)
> +		writel(BMC_DIAG_INTERRUPT_MASK, diag_status_reg_addr);
> +}
> +
> +static void a64fx_diag_interrupt_enable(struct a64fx_diag_priv *priv)
> +{
> +	u32 mmsc;
> +	void __iomem *diag_enable_reg_addr;
> +
> +	diag_enable_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_ENABLE_OFFSET;
> +	mmsc = readl(diag_enable_reg_addr);
> +	if (!(mmsc & BMC_DIAG_INTERRUPT_MASK)) {
> +		mmsc |= BMC_DIAG_INTERRUPT_MASK;
> +		writel(mmsc, diag_enable_reg_addr);
> +	}
> +}
> +
> +static void a64fx_diag_interrupt_disable(struct a64fx_diag_priv *priv)
> +{
> +	u32 mmsc;
> +	void __iomem *diag_enable_reg_addr;
> +
> +	diag_enable_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_ENABLE_OFFSET;
> +	mmsc = readl(diag_enable_reg_addr);
> +	if (mmsc & BMC_DIAG_INTERRUPT_MASK) {
> +		mmsc &= ~BMC_DIAG_INTERRUPT_MASK;
> +		writel(mmsc, diag_enable_reg_addr);
> +	}
> +}
> +
> +static int a64fx_diag_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	unsigned long irq_flags;
> +	struct device *dev = &pdev->dev;
> +	struct a64fx_diag_priv *priv;
> +
> +	priv = devm_kzalloc(dev, sizeof(struct a64fx_diag_priv), GFP_KERNEL);

Don't we prefer sizeof(*priv)?

> +	if (priv == NULL)
> +		return -ENOMEM;
> +
> +	priv->mmsc_reg_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(priv->mmsc_reg_base))
> +		return PTR_ERR(priv->mmsc_reg_base);
> +
> +	priv->irq = platform_get_irq(pdev, A64FX_DIAG_IRQ);
> +	if (priv->irq < 0)
> +		return priv->irq;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	a64fx_diag_interrupt_clear(priv);
> +	a64fx_diag_interrupt_enable(priv);
> +
> +	irq_flags = IRQF_PERCPU | IRQF_NOBALANCING | IRQF_NO_AUTOEN |
> +		   IRQF_NO_THREAD;
> +	ret = request_nmi(priv->irq, &a64fx_diag_handler_nmi, irq_flags,
> +			"a64fx_diag_nmi", NULL);
> +	if (ret) {
> +		ret = request_irq(priv->irq, &a64fx_diag_handler_irq,
> +				irq_flags, "a64fx_diag_irq", NULL);
> +		if (ret) {
> +			dev_err(dev, "cannot register IRQ %d\n", ret);

No a64fx_diag_interrupt_disable()?

> +			return ret;
> +		}
> +		enable_irq(priv->irq);

Hmm...

> +		priv->has_nmi = false;

No need to set zeroed priv member to zero.

> +	} else {
> +		enable_nmi(priv->irq);

Provided the above, I don't immediatelly see, what's the purpose of 
IRQF_NO_AUTOEN then?

> +		priv->has_nmi = true;
> +	}
> +
> +	return 0;
> +}
> +
> +static int __exit a64fx_diag_remove(struct platform_device *pdev)

Is __exit appropriate here at all -- I doubt that.

> +{
> +	struct a64fx_diag_priv *priv = platform_get_drvdata(pdev);
> +
> +	a64fx_diag_interrupt_disable(priv);
> +	a64fx_diag_interrupt_clear(priv);
> +
> +	if (priv->has_nmi)
> +		free_nmi(priv->irq, NULL);
> +	else
> +		free_irq(priv->irq, NULL);
> +
> +	return 0;
> +}
> +
> +static const struct acpi_device_id a64fx_diag_acpi_match[] = {
> +	{ "FUJI2007", 0 },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(acpi, a64fx_diag_acpi_match);
> +
> +
> +static struct platform_driver a64fx_diag_driver = {
> +	.driver = {
> +		.name = "a64fx_diag_driver",
> +		.acpi_match_table = ACPI_PTR(a64fx_diag_acpi_match),
> +	},
> +	.probe = a64fx_diag_probe,
> +	.remove = a64fx_diag_remove,
> +};
> +
> +module_platform_driver(a64fx_diag_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Hitomi Hasegawa <hasegawa-hitomi@...itsu.com>");
> +MODULE_DESCRIPTION("A64FX diag driver");


-- 
js
suse labs

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