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

[Ilkka Koskinen <ilkka@os.amperecomputing.com>]

Hi Lorenzo,

On Wed, 5 Jan 2022, Lorenzo Pieralisi wrote:
> [+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 <ilkka@os.amperecomputing.com>
>> ---
>>  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.

I clean them

>
>> +
>> +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 ?

Well, I guess I thought to have a device/driver to handle SDEI events and 
interrupts since the spec calls it a device. I can certainly remove those, 
if that's preferred.

>
>> +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.

That's a good point. I change it.

>
>> +
>> +	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 ?

Yes, that's the reason. AGDI table is missing flags that would define 
trigger type and polarity.

>
>> +		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
>

Cheers, Ilkka