platform/x86/amd: Add support for AMD ACPI based Wifi band RFI mitigation feature

Due to electrical and mechanical constraints in certain platform designs
there may be likely interference of relatively high-powered harmonics of
the (G-)DDR memory clocks with local radio module frequency bands used
by Wifi 6/6e/7.

To mitigate this, AMD has introduced a mechanism that devices can use to
notify active use of particular frequencies so that other devices can make
relative internal adjustments as necessary to avoid this resonance.

Co-developed-by: Evan Quan <[email protected]>
Signed-off-by: Evan Quan <[email protected]>
Signed-off-by: Ma Jun <[email protected]>
Reviewed-by: Mario Limonciello <[email protected]>
Reviewed-by: Hans de Goede <[email protected]>
Signed-off-by: Hans de Goede <[email protected]>

Author: Ma Jun

drivers/platform/x86/amd/Kconfig

@@ -18,3 +18,17 @@ config AMD_HSMP
 
 	  If you choose to compile this driver as a module the module will be
 	  called amd_hsmp.
+
+config AMD_WBRF
+	bool "AMD Wifi RF Band mitigations (WBRF)"
+	depends on ACPI
+	help
+	  WBRF(Wifi Band RFI mitigation) mechanism allows Wifi drivers
+	  to notify the frequencies they are using so that other hardware
+	  can be reconfigured to avoid harmonic conflicts.
+
+	  AMD provides an ACPI based mechanism to support WBRF on platform with
+	  appropriate underlying support.
+
+	  This mechanism will only be activated on platforms that advertise a
+	  need for it.

drivers/platform/x86/amd/Makefile

@@ -8,3 +8,4 @@ obj-$(CONFIG_AMD_PMC)		+= pmc/
 amd_hsmp-y			:= hsmp.o
 obj-$(CONFIG_AMD_HSMP)		+= amd_hsmp.o
 obj-$(CONFIG_AMD_PMF)		+= pmf/
+obj-$(CONFIG_AMD_WBRF)		+= wbrf.o

drivers/platform/x86/amd/wbrf.c

@@ -0,0 +1,317 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Wifi Frequency Band Manage Interface
+ * Copyright (C) 2023 Advanced Micro Devices
+ */
+
+#include <linux/acpi.h>
+#include <linux/acpi_amd_wbrf.h>
+
+/*
+ * Functions bit vector for WBRF method
+ *
+ * Bit 0: WBRF supported.
+ * Bit 1: Function 1 (Add / Remove frequency) is supported.
+ * Bit 2: Function 2 (Get frequency list) is supported.
+ */
+#define WBRF_ENABLED		0x0
+#define WBRF_RECORD			0x1
+#define WBRF_RETRIEVE		0x2
+
+#define WBRF_REVISION		0x1
+
+/*
+ * The data structure used for WBRF_RETRIEVE is not naturally aligned.
+ * And unfortunately the design has been settled down.
+ */
+struct amd_wbrf_ranges_out {
+	u32			num_of_ranges;
+	struct freq_band_range	band_list[MAX_NUM_OF_WBRF_RANGES];
+} __packed;
+
+static const guid_t wifi_acpi_dsm_guid =
+	GUID_INIT(0x7b7656cf, 0xdc3d, 0x4c1c,
+		  0x83, 0xe9, 0x66, 0xe7, 0x21, 0xde, 0x30, 0x70);
+
+/*
+ * Used to notify consumer (amdgpu driver currently) about
+ * the wifi frequency is change.
+ */
+static BLOCKING_NOTIFIER_HEAD(wbrf_chain_head);
+
+static int wbrf_record(struct acpi_device *adev, uint8_t action, struct wbrf_ranges_in_out *in)
+{
+	union acpi_object argv4;
+	union acpi_object *tmp;
+	union acpi_object *obj;
+	u32 num_of_ranges = 0;
+	u32 num_of_elements;
+	u32 arg_idx = 0;
+	int ret;
+	u32 i;
+
+	if (!in)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(in->band_list); i++) {
+		if (in->band_list[i].start && in->band_list[i].end)
+			num_of_ranges++;
+	}
+
+	/*
+	 * The num_of_ranges value in the "in" object supplied by
+	 * the caller is required to be equal to the number of
+	 * entries in the band_list array in there.
+	 */
+	if (num_of_ranges != in->num_of_ranges)
+		return -EINVAL;
+
+	/*
+	 * Every input frequency band comes with two end points(start/end)
+	 * and each is accounted as an element. Meanwhile the range count
+	 * and action type are accounted as an element each.
+	 * So, the total element count = 2 * num_of_ranges + 1 + 1.
+	 */
+	num_of_elements = 2 * num_of_ranges + 2;
+
+	tmp = kcalloc(num_of_elements, sizeof(*tmp), GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+
+	argv4.package.type = ACPI_TYPE_PACKAGE;
+	argv4.package.count = num_of_elements;
+	argv4.package.elements = tmp;
+
+	/* save the number of ranges*/
+	tmp[0].integer.type = ACPI_TYPE_INTEGER;
+	tmp[0].integer.value = num_of_ranges;
+
+	/* save the action(WBRF_RECORD_ADD/REMOVE/RETRIEVE) */
+	tmp[1].integer.type = ACPI_TYPE_INTEGER;
+	tmp[1].integer.value = action;
+
+	arg_idx = 2;
+	for (i = 0; i < ARRAY_SIZE(in->band_list); i++) {
+		if (!in->band_list[i].start || !in->band_list[i].end)
+			continue;
+
+		tmp[arg_idx].integer.type = ACPI_TYPE_INTEGER;
+		tmp[arg_idx++].integer.value = in->band_list[i].start;
+		tmp[arg_idx].integer.type = ACPI_TYPE_INTEGER;
+		tmp[arg_idx++].integer.value = in->band_list[i].end;
+	}
+
+	obj = acpi_evaluate_dsm(adev->handle, &wifi_acpi_dsm_guid,
+				WBRF_REVISION, WBRF_RECORD, &argv4);
+
+	if (!obj)
+		return -EINVAL;
+
+	if (obj->type != ACPI_TYPE_INTEGER) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = obj->integer.value;
+	if (ret)
+		ret = -EINVAL;
+
+out:
+	ACPI_FREE(obj);
+	kfree(tmp);
+
+	return ret;
+}
+
+/**
+ * acpi_amd_wbrf_add_remove - add or remove the frequency band the device is using
+ *
+ * @dev: device pointer
+ * @action: remove or add the frequency band into bios
+ * @in: input structure containing the frequency band the device is using
+ *
+ * Broadcast to other consumers the frequency band the device starts
+ * to use. Underneath the surface the information is cached into an
+ * internal buffer first. Then a notification is sent to all those
+ * registered consumers. So then they can retrieve that buffer to
+ * know the latest active frequency bands. Consumers that haven't
+ * yet been registered can retrieve the information from the cache
+ * when they register.
+ *
+ * Return:
+ * 0 for success add/remove wifi frequency band.
+ * Returns a negative error code for failure.
+ */
+int acpi_amd_wbrf_add_remove(struct device *dev, uint8_t action, struct wbrf_ranges_in_out *in)
+{
+	struct acpi_device *adev;
+	int ret;
+
+	adev = ACPI_COMPANION(dev);
+	if (!adev)
+		return -ENODEV;
+
+	ret = wbrf_record(adev, action, in);
+	if (ret)
+		return ret;
+
+	blocking_notifier_call_chain(&wbrf_chain_head, WBRF_CHANGED, NULL);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(acpi_amd_wbrf_add_remove);
+
+/**
+ * acpi_amd_wbrf_supported_producer - determine if the WBRF can be enabled
+ *                                    for the device as a producer
+ *
+ * @dev: device pointer
+ *
+ * Check if the platform equipped with necessary implementations to
+ * support WBRF for the device as a producer.
+ *
+ * Return:
+ * true if WBRF is supported, otherwise returns false
+ */
+bool acpi_amd_wbrf_supported_producer(struct device *dev)
+{
+	struct acpi_device *adev;
+
+	adev = ACPI_COMPANION(dev);
+	if (!adev)
+		return false;
+
+	return acpi_check_dsm(adev->handle, &wifi_acpi_dsm_guid,
+			      WBRF_REVISION, BIT(WBRF_RECORD));
+}
+EXPORT_SYMBOL_GPL(acpi_amd_wbrf_supported_producer);
+
+/**
+ * acpi_amd_wbrf_supported_consumer - determine if the WBRF can be enabled
+ *                                    for the device as a consumer
+ *
+ * @dev: device pointer
+ *
+ * Determine if the platform equipped with necessary implementations to
+ * support WBRF for the device as a consumer.
+ *
+ * Return:
+ * true if WBRF is supported, otherwise returns false.
+ */
+bool acpi_amd_wbrf_supported_consumer(struct device *dev)
+{
+	struct acpi_device *adev;
+
+	adev = ACPI_COMPANION(dev);
+	if (!adev)
+		return false;
+
+	return acpi_check_dsm(adev->handle, &wifi_acpi_dsm_guid,
+			      WBRF_REVISION, BIT(WBRF_RETRIEVE));
+}
+EXPORT_SYMBOL_GPL(acpi_amd_wbrf_supported_consumer);
+
+/**
+ * amd_wbrf_retrieve_freq_band - retrieve current active frequency bands
+ *
+ * @dev: device pointer
+ * @out: output structure containing all the active frequency bands
+ *
+ * Retrieve the current active frequency bands which were broadcasted
+ * by other producers. The consumer who calls this API should take
+ * proper actions if any of the frequency band may cause RFI with its
+ * own frequency band used.
+ *
+ * Return:
+ * 0 for getting wifi freq band successfully.
+ * Returns a negative error code for failure.
+ */
+int amd_wbrf_retrieve_freq_band(struct device *dev, struct wbrf_ranges_in_out *out)
+{
+	struct amd_wbrf_ranges_out acpi_out = {0};
+	struct acpi_device *adev;
+	union acpi_object *obj;
+	union acpi_object param;
+	int ret = 0;
+
+	adev = ACPI_COMPANION(dev);
+	if (!adev)
+		return -ENODEV;
+
+	param.type = ACPI_TYPE_STRING;
+	param.string.length = 0;
+	param.string.pointer = NULL;
+
+	obj = acpi_evaluate_dsm(adev->handle, &wifi_acpi_dsm_guid,
+							WBRF_REVISION, WBRF_RETRIEVE, &param);
+	if (!obj)
+		return -EINVAL;
+
+	/*
+	 * The return buffer is with variable length and the format below:
+	 * number_of_entries(1 DWORD):       Number of entries
+	 * start_freq of 1st entry(1 QWORD): Start frequency of the 1st entry
+	 * end_freq of 1st entry(1 QWORD):   End frequency of the 1st entry
+	 * ...
+	 * ...
+	 * start_freq of the last entry(1 QWORD)
+	 * end_freq of the last entry(1 QWORD)
+	 *
+	 * Thus the buffer length is determined by the number of entries.
+	 * - For zero entry scenario, the buffer length will be 4 bytes.
+	 * - For one entry scenario, the buffer length will be 20 bytes.
+	 */
+	if (obj->buffer.length > sizeof(acpi_out) || obj->buffer.length < 4) {
+		dev_err(dev, "Wrong sized WBRT information");
+		ret = -EINVAL;
+		goto out;
+	}
+	memcpy(&acpi_out, obj->buffer.pointer, obj->buffer.length);
+
+	out->num_of_ranges = acpi_out.num_of_ranges;
+	memcpy(out->band_list, acpi_out.band_list, sizeof(acpi_out.band_list));
+
+out:
+	ACPI_FREE(obj);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(amd_wbrf_retrieve_freq_band);
+
+/**
+ * amd_wbrf_register_notifier - register for notifications of frequency
+ *                                   band update
+ *
+ * @nb: driver notifier block
+ *
+ * The consumer should register itself via this API so that it can get
+ * notified on the frequency band updates from other producers.
+ *
+ * Return:
+ * 0 for registering a consumer driver successfully.
+ * Returns a negative error code for failure.
+ */
+int amd_wbrf_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&wbrf_chain_head, nb);
+}
+EXPORT_SYMBOL_GPL(amd_wbrf_register_notifier);
+
+/**
+ * amd_wbrf_unregister_notifier - unregister for notifications of
+ *                                     frequency band update
+ *
+ * @nb: driver notifier block
+ *
+ * The consumer should call this API when it is longer interested with
+ * the frequency band updates from other producers. Usually, this should
+ * be performed during driver cleanup.
+ *
+ * Return:
+ * 0 for unregistering a consumer driver.
+ * Returns a negative error code for failure.
+ */
+int amd_wbrf_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&wbrf_chain_head, nb);
+}
+EXPORT_SYMBOL_GPL(amd_wbrf_unregister_notifier);