Subject: Re: [PATCH v3 2/2] ACPI: AGDI: Add driver for Arm Generic Diagnostic Dump and Reset device

From: Lorenzo Pieralisi <[email-masked]>
Date: Wed, 5 Jan 2022 10:46:02 +0000

[+James, for SDEI bits]

On Thu, Dec 30, 2021 at 07:37:25PM -0800, Ilkka Koskinen wrote:
> ACPI for Arm Components 1.1 Platform Design Document v1.1 [0] specifices
> Arm Generic Diagnostic Device Interface (AGDI). It allows an admin to
> issue diagnostic dump and reset via an SDEI event or an interrupt.
> This patch implements SDEI path.
> 
> [0] https://developer.arm.com/documentation/den0093/latest/
> 
> Signed-off-by: Ilkka Koskinen <[email-masked]>
> ---
>  drivers/acpi/arm64/Kconfig  |   8 +++
>  drivers/acpi/arm64/Makefile |   1 +
>  drivers/acpi/arm64/agdi.c   | 125 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 134 insertions(+)
>  create mode 100644 drivers/acpi/arm64/agdi.c
> 
> diff --git a/drivers/acpi/arm64/Kconfig b/drivers/acpi/arm64/Kconfig
> index 6dba187f4f2e..24869ba5b365 100644
> --- a/drivers/acpi/arm64/Kconfig
> +++ b/drivers/acpi/arm64/Kconfig
> @@ -8,3 +8,11 @@ config ACPI_IORT
>  
>  config ACPI_GTDT
>  	bool
> +
> +config ACPI_AGDI
> +	bool "Arm Generic Diagnostic Dump and Reset Device Interface"
> +	depends on ARM_SDE_INTERFACE
> +	help
> +	  Arm Generic Diagnostic Dump and Reset Device Interface (AGDI) is
> +	  a standard that enables issuing a non-maskable diagnostic dump and
> +	  reset command.
> diff --git a/drivers/acpi/arm64/Makefile b/drivers/acpi/arm64/Makefile
> index 66acbe77f46e..7b9e4045659d 100644
> --- a/drivers/acpi/arm64/Makefile
> +++ b/drivers/acpi/arm64/Makefile
> @@ -1,4 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_ACPI_AGDI) 	+= agdi.o
>  obj-$(CONFIG_ACPI_IORT) 	+= iort.o
>  obj-$(CONFIG_ACPI_GTDT) 	+= gtdt.o
>  obj-y				+= dma.o
> diff --git a/drivers/acpi/arm64/agdi.c b/drivers/acpi/arm64/agdi.c
> new file mode 100644
> index 000000000000..6525ccbae5c1
> --- /dev/null
> +++ b/drivers/acpi/arm64/agdi.c
> @@ -0,0 +1,125 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * This file implements handling of
> + * Arm Generic Diagnostic Dump and Reset Interface table (AGDI)
> + *
> + * Copyright (c) 2021, Ampere Computing LLC
> + */
> +
> +#define pr_fmt(fmt) "ACPI: AGDI: " fmt
> +
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/acpi.h>
> +#include <linux/arm_sdei.h>
> +#include <linux/io.h>

Nit: alphabetical order.

> +
> +struct agdi_data {
> +	int sdei_event;
> +};
> +
> +static int agdi_sdei_handler(u32 sdei_event, struct pt_regs *regs, void *arg)
> +{
> +	nmi_panic(regs, "Arm Generic Diagnostic Dump and Reset SDEI event issued");
> +	return 0;
> +}
> +
> +static int agdi_sdei_probe(struct platform_device *pdev,
> +			   struct agdi_data *adata)
> +{
> +	int err;
> +
> +	err = sdei_event_register(adata->sdei_event, agdi_sdei_handler, pdev);
> +	if (err) {
> +		dev_err(&pdev->dev, "Failed to register for SDEI event %d",
> +			adata->sdei_event);
> +		return err;
> +	}
> +
> +	err = sdei_event_enable(adata->sdei_event);
> +	if (err)  {
> +		sdei_event_unregister(adata->sdei_event);
> +		dev_err(&pdev->dev, "Failed to enable event %d\n",
> +			adata->sdei_event);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int agdi_probe(struct platform_device *pdev)
> +{
> +	struct agdi_data *adata;
> +
> +	adata = dev_get_platdata(&pdev->dev);
> +	if (!adata)
> +		return -EINVAL;
> +
> +	return agdi_sdei_probe(pdev, adata);
> +}
> +
> +static int agdi_remove(struct platform_device *pdev)
> +{
> +	struct agdi_data *adata = platform_get_drvdata(pdev);
> +
> +	sdei_event_disable(adata->sdei_event);
> +	sdei_event_unregister(adata->sdei_event);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver agdi_driver = {
> +	.driver = {
> +		.name = "agdi",
> +	},
> +	.probe = agdi_probe,
> +	.remove = agdi_remove,
> +};

May I ask why we need a platform device (and driver) to register
an SDEI event ?

> +static int __init agdi_init(void)
> +{
> +	int ret;
> +	acpi_status status;
> +	struct acpi_table_agdi *agdi_table;
> +	struct agdi_data pdata;
> +	struct platform_device *pdev;
> +
> +	if (acpi_disabled)
> +		return 0;

Why don't we call agdi_init() from acpi_init() as we do for IORT/VIOT ?

I don't think it is necessary to add a device_initcall(), with related
ordering dependencies.

> +
> +	status = acpi_get_table(ACPI_SIG_AGDI, 0,
> +				(struct acpi_table_header **) &agdi_table);
> +	if (ACPI_FAILURE(status))
> +		return -ENODEV;
> +
> +	if (agdi_table->flags & ACPI_AGDI_SIGNALING_MODE) {

Is this because specs need updating ?

> +		pr_warn("Interrupt signaling is not supported");
> +		ret = -ENODEV;
> +		goto err_put_table;
> +	}
> +
> +	pdata.sdei_event = agdi_table->sdei_event;
> +
> +	pdev = platform_device_register_data(NULL, "agdi", 0, &pdata, sizeof(pdata));
> +	if (IS_ERR(pdev)) {
> +		ret = PTR_ERR(pdev);
> +		goto err_put_table;
> +	}
> +
> +	ret = platform_driver_register(&agdi_driver);
> +	if (ret)
> +		goto err_device_unregister;
> +
> +	acpi_put_table((struct acpi_table_header *)agdi_table);
> +	return 0;
> +
> +err_device_unregister:
> +	platform_device_unregister(pdev);
> +err_put_table:
> +	acpi_put_table((struct acpi_table_header *)agdi_table);
> +	return ret;
> +}
> +device_initcall(agdi_init);

See above.

Thanks,
Lorenzo

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