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References: <20220304064324.331217-1-hasegawa-hitomi@fujitsu.com> <20220304064324.331217-3-hasegawa-hitomi@fujitsu.com>
In-Reply-To: <20220304064324.331217-3-hasegawa-hitomi@fujitsu.com>
From:   Sumit Garg <sumit.garg@linaro.org>
Date:   Mon, 7 Mar 2022 17:19:44 +0530
Message-ID: <CAFA6WYMESyto9bFtk2qNBMi40BkJOoUKpYtAScXjb3yunhHTJA@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] soc: fujitsu: Add A64FX diagnostic interrupt driver
To:     Hitomi Hasegawa <hasegawa-hitomi@fujitsu.com>
Cc:     linux-arm-kernel@lists.infradead.org, soc@kernel.org,
        linux-serial@vger.kernel.org, arnd@arndb.de, olof@lixom.net,
        catalin.marinas@arm.com, will@kernel.org,
        gregkh@linuxfoundation.org, jirislaby@kernel.org,
        jason.wessel@windriver.com, daniel.thompson@linaro.org,
        dianders@chromium.org, linux-kernel@vger.kernel.org,
        kgdb-bugreport@lists.sourceforge.net, peterz@infradead.org
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Precedence: bulk

Hi Hitomi,

On Fri, 4 Mar 2022 at 12:15, Hitomi Hasegawa
<hasegawa-hitomi@fujitsu.com> wrote:
>
> Enable diagnostic interrupts for the A64FX.
> This is done using a pseudo-NMI.
>
> Signed-off-by: Hitomi Hasegawa <hasegawa-hitomi@fujitsu.com>
> ---
>  MAINTAINERS                      |   5 +
>  drivers/soc/Kconfig              |   1 +
>  drivers/soc/Makefile             |   1 +
>  drivers/soc/fujitsu/Kconfig      |  13 +++
>  drivers/soc/fujitsu/Makefile     |   3 +
>  drivers/soc/fujitsu/a64fx-diag.c | 151 +++++++++++++++++++++++++++++++
>  6 files changed, 174 insertions(+)
>  create mode 100644 drivers/soc/fujitsu/Kconfig
>  create mode 100644 drivers/soc/fujitsu/Makefile
>  create mode 100644 drivers/soc/fujitsu/a64fx-diag.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index dd36acc87ce6..e9663fa92a52 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -239,6 +239,11 @@ 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
> diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
> index e8a30c4c5aec..0405ff0b3be6 100644
> --- a/drivers/soc/Kconfig
> +++ b/drivers/soc/Kconfig
> @@ -8,6 +8,7 @@ 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"
> diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
> index a05e9fbcd3e0..86596405a39c 100644
> --- a/drivers/soc/Makefile
> +++ b/drivers/soc/Makefile
> @@ -11,6 +11,7 @@ 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/
> diff --git a/drivers/soc/fujitsu/Kconfig b/drivers/soc/fujitsu/Kconfig
> new file mode 100644
> index 000000000000..b41cdac67637
> --- /dev/null
> +++ b/drivers/soc/fujitsu/Kconfig
> @@ -0,0 +1,13 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +menu "fujitsu SoC drivers"
> +
> +config A64FX_DIAG
> +       bool "A64FX diag driver"
> +       depends on ARM64
> +       help
> +         Say Y here if you want to enable diag interrupt on A64FX.
> +         This driver uses pseudo-NMI if available.
> +
> +         If unsure, say N.
> +
> +endmenu
> diff --git a/drivers/soc/fujitsu/Makefile b/drivers/soc/fujitsu/Makefile
> new file mode 100644
> index 000000000000..945bc1c14ad0
> --- /dev/null
> +++ b/drivers/soc/fujitsu/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_A64FX_DIAG)       += a64fx-diag.o
> diff --git a/drivers/soc/fujitsu/a64fx-diag.c b/drivers/soc/fujitsu/a64fx-diag.c
> new file mode 100644
> index 000000000000..c6f895cf8912
> --- /dev/null
> +++ b/drivers/soc/fujitsu/a64fx-diag.c
> @@ -0,0 +1,151 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * A64FX diag driver.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/sysrq.h>
> +
> +#define A64FX_DIAG_IRQ 1
> +#define BMC_DIAG_INTERRUPT_STATUS_OFFSET (0x0044)
> +#define BMC_INTERRUPT_STATUS_MASK ((1U) << 31)
> +#define BMC_DIAG_INTERRUPT_ENABLE_OFFSET (0x0040)
> +#define BMC_INTERRUPT_ENABLE_MASK ((1U) << 31)
> +
> +struct a64fx_diag_priv {
> +       int irq;
> +       void __iomem *mmsc_reg_base;
> +       bool has_nmi;
> +};
> +
> +static irqreturn_t a64fx_diag_handler(int irq, void *dev_id)
> +{
> +       handle_sysrq('c');
> +

Would it be possible to pass a dynamic sysrq key from BMC to the host
as that would unleash the true power of sysrq in an NMI context
capable of launching kdb as one example?

-Sumit

> +       return IRQ_HANDLED;
> +}
> +
> +static void a64fx_diag_interrupt_clear(struct a64fx_diag_priv *priv)
> +{
> +       u32 mmsc;
> +       const void __iomem *diag_status_reg_addr;
> +
> +       diag_status_reg_addr = priv->mmsc_reg_base + BMC_DIAG_INTERRUPT_STATUS_OFFSET;
> +       mmsc = readl(diag_status_reg_addr);
> +       if (mmsc & BMC_INTERRUPT_STATUS_MASK)
> +               writel(BMC_INTERRUPT_STATUS_MASK, (void *)diag_status_reg_addr);
> +}
> +
> +static void a64fx_diag_interrupt_enable(struct a64fx_diag_priv *priv)
> +{
> +       u32 mmsc;
> +       const 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_INTERRUPT_ENABLE_MASK)) {
> +               mmsc |= BMC_INTERRUPT_STATUS_MASK;
> +               writel(mmsc, (void *)diag_enable_reg_addr);
> +       }
> +}
> +
> +static void a64fx_diag_interrupt_disable(struct a64fx_diag_priv *priv)
> +{
> +       u32 mmsc;
> +       const 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_INTERRUPT_ENABLE_MASK) {
> +               mmsc &= ~BMC_INTERRUPT_ENABLE_MASK;
> +               writel(mmsc, (void *)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);
> +       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, irq_flags,
> +                       "a64fx_diag_nmi", NULL);
> +       if (ret) {
> +               ret = request_irq(priv->irq, &a64fx_diag_handler,
> +                               irq_flags, "a64fx_diag_irq", NULL);
> +               if (ret) {
> +                       dev_err(dev, "cannot register IRQ %d\n", ret);
> +                       return ret;
> +               }
> +               enable_irq(priv->irq);
> +               priv->has_nmi = false;
> +               dev_info(dev, "registered for IRQ %d\n", priv->irq);
> +       } else {
> +               enable_nmi(priv->irq);
> +               priv->has_nmi = true;
> +               dev_info(dev, "registered for NMI %d\n", priv->irq);
> +       }
> +
> +       return 0;
> +}
> +
> +static int __exit 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");
> --
> 2.27.0
>