acpi_adxl.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Address translation interface via ACPI DSM.
 * Copyright (C) 2018 Intel Corporation
 *
 * Specification for this interface is available at:
 *
 *	https://cdrdv2.intel.com/v1/dl/getContent/603354
 */

#include <linux/acpi.h>
#include <linux/adxl.h>

#define ADXL_REVISION			0x1
#define ADXL_IDX_GET_ADDR_PARAMS	0x1
#define ADXL_IDX_FORWARD_TRANSLATE	0x2
#define ACPI_ADXL_PATH			"\\_SB.ADXL"

/*
 * The specification doesn't provide a limit on how many
 * components are in a memory address. But since we allocate
 * memory based on the number the BIOS tells us, we should
 * defend against insane values.
 */
#define ADXL_MAX_COMPONENTS		500

#undef pr_fmt
#define pr_fmt(fmt) "ADXL: " fmt

static acpi_handle handle;
static union acpi_object *params;
static const guid_t adxl_guid =
	GUID_INIT(0xAA3C050A, 0x7EA4, 0x4C1F,
		  0xAF, 0xDA, 0x12, 0x67, 0xDF, 0xD3, 0xD4, 0x8D);

static int adxl_count;
static char **adxl_component_names;

static union acpi_object *adxl_dsm(int cmd, union acpi_object argv[])
{
	union acpi_object *obj, *o;

	obj = acpi_evaluate_dsm_typed(handle, &adxl_guid, ADXL_REVISION,
				      cmd, argv, ACPI_TYPE_PACKAGE);
	if (!obj) {
		pr_info("DSM call failed for cmd=%d\n", cmd);
		return NULL;
	}

	if (obj->package.count != 2) {
		pr_info("Bad pkg count %d\n", obj->package.count);
		goto err;
	}

	o = obj->package.elements;
	if (o->type != ACPI_TYPE_INTEGER) {
		pr_info("Bad 1st element type %d\n", o->type);
		goto err;
	}
	if (o->integer.value) {
		pr_info("Bad ret val %llu\n", o->integer.value);
		goto err;
	}

	o = obj->package.elements + 1;
	if (o->type != ACPI_TYPE_PACKAGE) {
		pr_info("Bad 2nd element type %d\n", o->type);
		goto err;
	}
	return obj;

err:
	ACPI_FREE(obj);
	return NULL;
}

/**
 * adxl_get_component_names - get list of memory component names
 * Returns NULL terminated list of string names
 *
 * Give the caller a pointer to the list of memory component names
 * e.g. { "SystemAddress", "ProcessorSocketId", "ChannelId", ... NULL }
 * Caller should count how many strings in order to allocate a buffer
 * for the return from adxl_decode().
 */
const char * const *adxl_get_component_names(void)
{
	return (const char * const *)adxl_component_names;
}
EXPORT_SYMBOL_GPL(adxl_get_component_names);

/**
 * adxl_decode - ask BIOS to decode a system address to memory address
 * @addr: the address to decode
 * @component_values: pointer to array of values for each component
 * Returns 0 on success, negative error code otherwise
 *
 * The index of each value returned in the array matches the index of
 * each component name returned by adxl_get_component_names().
 * Components that are not defined for this address translation (e.g.
 * mirror channel number for a non-mirrored address) are set to ~0ull.
 */
int adxl_decode(u64 addr, u64 component_values[])
{
	union acpi_object argv4[2], *results, *r;
	int i, cnt;

	if (!adxl_component_names)
		return -EOPNOTSUPP;

	argv4[0].type = ACPI_TYPE_PACKAGE;
	argv4[0].package.count = 1;
	argv4[0].package.elements = &argv4[1];
	argv4[1].integer.type = ACPI_TYPE_INTEGER;
	argv4[1].integer.value = addr;

	results = adxl_dsm(ADXL_IDX_FORWARD_TRANSLATE, argv4);
	if (!results)
		return -EINVAL;

	r = results->package.elements + 1;
	cnt = r->package.count;
	if (cnt != adxl_count) {
		ACPI_FREE(results);
		return -EINVAL;
	}
	r = r->package.elements;

	for (i = 0; i < cnt; i++)
		component_values[i] = r[i].integer.value;

	ACPI_FREE(results);

	return 0;
}
EXPORT_SYMBOL_GPL(adxl_decode);

static int __init adxl_init(void)
{
	char *path = ACPI_ADXL_PATH;
	union acpi_object *p;
	acpi_status status;
	int i;

	status = acpi_get_handle(NULL, path, &handle);
	if (ACPI_FAILURE(status)) {
		pr_debug("No ACPI handle for path %s\n", path);
		return -ENODEV;
	}

	if (!acpi_has_method(handle, "_DSM")) {
		pr_info("No DSM method\n");
		return -ENODEV;
	}

	if (!acpi_check_dsm(handle, &adxl_guid, ADXL_REVISION,
			    ADXL_IDX_GET_ADDR_PARAMS |
			    ADXL_IDX_FORWARD_TRANSLATE)) {
		pr_info("DSM method does not support forward translate\n");
		return -ENODEV;
	}

	params = adxl_dsm(ADXL_IDX_GET_ADDR_PARAMS, NULL);
	if (!params) {
		pr_info("Failed to get component names\n");
		return -ENODEV;
	}

	p = params->package.elements + 1;
	adxl_count = p->package.count;
	if (adxl_count > ADXL_MAX_COMPONENTS) {
		pr_info("Insane number of address component names %d\n", adxl_count);
		ACPI_FREE(params);
		return -ENODEV;
	}
	p = p->package.elements;

	/*
	 * Allocate one extra for NULL termination.
	 */
	adxl_component_names = kcalloc(adxl_count + 1, sizeof(char *), GFP_KERNEL);
	if (!adxl_component_names) {
		ACPI_FREE(params);
		return -ENOMEM;
	}

	for (i = 0; i < adxl_count; i++)
		adxl_component_names[i] = p[i].string.pointer;

	return 0;
}
subsys_initcall(adxl_init);