soc: fujitsu: Add A64FX diagnostic interrupt driver

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@fujitsu.com>
Link: https://lore.kernel.org/r/20220520074119.3574753-2-hasegawa-hitomi@fujitsu.com'
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -242,6 +242,11 @@ F:	include/trace/events/9p.h
 F:	include/uapi/linux/virtio_9p.h
 F:	net/9p/
 
+A64FX DIAG DRIVER
+M:	Hitomi Hasegawa <hasegawa-hitomi@fujitsu.com>
+S:	Supported
+F:	drivers/soc/fujitsu/a64fx-diag.c
+
 A8293 MEDIA DRIVER
 M:	Antti Palosaari <crope@iki.fi>
 L:	linux-media@vger.kernel.org

drivers/soc/Kconfig

@@ -9,6 +9,7 @@ source "drivers/soc/atmel/Kconfig"
 source "drivers/soc/bcm/Kconfig"
 source "drivers/soc/canaan/Kconfig"
 source "drivers/soc/fsl/Kconfig"
+source "drivers/soc/fujitsu/Kconfig"
 source "drivers/soc/imx/Kconfig"
 source "drivers/soc/ixp4xx/Kconfig"
 source "drivers/soc/litex/Kconfig"

drivers/soc/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_SOC_CANAAN)	+= canaan/
 obj-$(CONFIG_ARCH_DOVE)		+= dove/
 obj-$(CONFIG_MACH_DOVE)		+= dove/
 obj-y				+= fsl/
+obj-y				+= fujitsu/
 obj-$(CONFIG_ARCH_GEMINI)	+= gemini/
 obj-y				+= imx/
 obj-y				+= ixp4xx/

drivers/soc/fujitsu/Kconfig

@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menu "fujitsu SoC drivers"
+
+config A64FX_DIAG
+	tristate "A64FX diag driver"
+	depends on ARM64
+	depends on ACPI
+	help
+	  Say Y here if you want to enable diag interrupt on Fujitsu A64FX.
+	  This driver enables BMC's diagnostic requests and enables
+	  A64FX-specific interrupts. This allows administrators to obtain
+	  kernel dumps via diagnostic requests using ipmitool, etc.
+
+	  If unsure, say N.
+
+endmenu

drivers/soc/fujitsu/Makefile

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_A64FX_DIAG)	+= a64fx-diag.o

drivers/soc/fujitsu/a64fx-diag.c

@@ -0,0 +1,154 @@
+// 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_ENABLE 0x40
+#define BMC_DIAG_INTERRUPT_STATUS 0x44
+#define BMC_DIAG_INTERRUPT_MASK BIT(31)
+
+struct a64fx_diag_priv {
+	void __iomem *mmsc_reg_base;
+	int irq;
+	bool has_nmi;
+};
+
+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)
+{
+	void __iomem *diag_status_reg_addr;
+	u32 mmsc;
+
+	diag_status_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_STATUS;
+	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)
+{
+	void __iomem *diag_enable_reg_addr;
+	u32 mmsc;
+
+	diag_enable_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_ENABLE;
+	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)
+{
+	void __iomem *diag_enable_reg_addr;
+	u32 mmsc;
+
+	diag_enable_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_ENABLE;
+	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)
+{
+	struct device *dev = &pdev->dev;
+	struct a64fx_diag_priv *priv;
+	unsigned long irq_flags;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	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);
+
+	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);
+			return ret;
+		}
+		enable_irq(priv->irq);
+	} else {
+		enable_nmi(priv->irq);
+		priv->has_nmi = true;
+	}
+
+	a64fx_diag_interrupt_clear(priv);
+	a64fx_diag_interrupt_enable(priv);
+
+	return 0;
+}
+
+static int a64fx_diag_remove(struct platform_device *pdev)
+{
+	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@fujitsu.com>");
+MODULE_DESCRIPTION("A64FX diag driver");