Re: [PATCH v12 2/9] platform/x86/amd: Add support for AMD ACPI based Wifi band RFI mitigation feature

[Ilpo Järvinen]

On Tue, 17 Oct 2023, Ma Jun wrote:

> 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 <quanliangl@xxxxxxxxxxx>
> Signed-off-by: Evan Quan <quanliangl@xxxxxxxxxxx>
> Signed-off-by: Ma Jun <Jun.Ma2@xxxxxxx>
> 
> --
> v11:
>  - fix typo(Simon)
> v12:
>  - Fix the code (Rafael)
>  - Move amd_wbrf.c to drivers/platform/x86/amd/wbrf.c
>  - Updated Evan's email because he's no longer at AMD.Thanks
> for his work in earlier versions.
> ---
>  drivers/platform/x86/amd/Kconfig  |  15 ++
>  drivers/platform/x86/amd/Makefile |   1 +
>  drivers/platform/x86/amd/wbrf.c   | 402 ++++++++++++++++++++++++++++++
>  include/linux/acpi_amd_wbrf.h     | 101 ++++++++
>  4 files changed, 519 insertions(+)
>  create mode 100644 drivers/platform/x86/amd/wbrf.c
>  create mode 100644 include/linux/acpi_amd_wbrf.h
> 
> diff --git a/drivers/platform/x86/amd/Kconfig b/drivers/platform/x86/amd/Kconfig
> index d9685aef0887..fa5a978a2d22 100644
> --- a/drivers/platform/x86/amd/Kconfig
> +++ b/drivers/platform/x86/amd/Kconfig
> @@ -32,3 +32,18 @@ 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
> +	default n
> +	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.
> diff --git a/drivers/platform/x86/amd/Makefile b/drivers/platform/x86/amd/Makefile
> index 65732f0a3913..62b98b048b17 100644
> --- a/drivers/platform/x86/amd/Makefile
> +++ b/drivers/platform/x86/amd/Makefile
> @@ -9,3 +9,4 @@ obj-$(CONFIG_AMD_PMC)		+= amd-pmc.o
>  amd_hsmp-y			:= hsmp.o
>  obj-$(CONFIG_AMD_HSMP)		+= amd_hsmp.o
>  obj-$(CONFIG_AMD_PMF)		+= pmf/
> +obj-$(CONFIG_AMD_WBRF)		+= wbrf.o
> diff --git a/drivers/platform/x86/amd/wbrf.c b/drivers/platform/x86/amd/wbrf.c
> new file mode 100644
> index 000000000000..fb414564f576
> --- /dev/null
> +++ b/drivers/platform/x86/amd/wbrf.c
> @@ -0,0 +1,402 @@
> +// 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>
> +
> +#define ACPI_AMD_WBRF_METHOD	"\\WBRF"
> +
> +/*
> + * 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;
> +	u32 loop_idx;
> +	int ret;
> +
> +	if (!in)
> +		return -EINVAL;
> +
> +	/*
> +	 * 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.
> +	 */
> +	for (loop_idx = 0; loop_idx < ARRAY_SIZE(in->band_list);
> +	     loop_idx++)

This fits easily to one line.

What extra information loop_idx provides over the usual i? I see zero 
extra value, only extra characters.

> +		if (in->band_list[loop_idx].start &&
> +		    in->band_list[loop_idx].end)

One line.

> +			num_of_ranges++;
> +
> +	if (num_of_ranges != in->num_of_ranges)
> +		return -EINVAL;

Can't you just exit in the loop directly?

Seriously, this v12 of your series and nobody has noticed any of these?

> +
> +	/*
> +	 * 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 (loop_idx = 0; loop_idx < ARRAY_SIZE(in->band_list);
> +	     loop_idx++) {

Ditto.

> +		if (!in->band_list[loop_idx].start ||
> +		    !in->band_list[loop_idx].end)
> +			continue;
> +
> +		tmp[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +		tmp[arg_idx++].integer.value = in->band_list[loop_idx].start;
> +		tmp[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +		tmp[arg_idx++].integer.value = in->band_list[loop_idx].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);

Remove the newline between ACPI_FREE and kfree.

> +
> +	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 = ACPI_COMPANION(dev);
> +	int ret;
> +
> +	if (!adev)
> +		return -ENODEV;

To make this much easier to read, put the assignment right before it's 
error handling, like this (it's 1 line more but much easier to follow):

	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);
> +
> +static bool acpi_amd_wbrf_supported_system(void)
> +{
> +	acpi_status status;
> +	acpi_handle handle;
> +
> +	status = acpi_get_handle(NULL, ACPI_AMD_WBRF_METHOD, &handle);
> +
> +	return ACPI_SUCCESS(status);
> +}
> +
> +/**
> + * 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 = ACPI_COMPANION(dev);
> +
> +	if (!adev)
> +		return false;

Ditto.

> +
> +	if (!acpi_amd_wbrf_supported_system())
> +		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);
> +
> +static union acpi_object *
> +acpi_evaluate_wbrf(acpi_handle handle, u64 rev, u64 func)
> +{
> +	acpi_status ret;
> +	struct acpi_buffer buf = {ACPI_ALLOCATE_BUFFER, NULL};
> +	union acpi_object params[4];
> +	struct acpi_object_list input = {
> +		.count = 4,
> +		.pointer = params,
> +	};
> +
> +	params[0].type = ACPI_TYPE_INTEGER;
> +	params[0].integer.value = rev;
> +	params[1].type = ACPI_TYPE_INTEGER;
> +	params[1].integer.value = func;
> +	params[2].type = ACPI_TYPE_PACKAGE;
> +	params[2].package.count = 0;
> +	params[2].package.elements = NULL;
> +	params[3].type = ACPI_TYPE_STRING;
> +	params[3].string.length = 0;
> +	params[3].string.pointer = NULL;
> +
> +	ret = acpi_evaluate_object(handle, "WBRF", &input, &buf);
> +	if (ACPI_FAILURE(ret))
> +		return NULL;
> +
> +	return buf.pointer;
> +}
> +
> +static bool check_acpi_wbrf(acpi_handle handle, u64 rev, u64 funcs)
> +{
> +	int i;
> +	u64 mask = 0;
> +	union acpi_object *obj;
> +
> +	if (funcs == 0)
> +		return false;
> +
> +	obj = acpi_evaluate_wbrf(handle, rev, 0);
> +	if (!obj)
> +		return false;
> +
> +	if (obj->type != ACPI_TYPE_BUFFER)
> +		return false;
> +
> +	/*
> +	 * Bit vector providing supported functions information.
> +	 * Each bit marks support for one specific function of the WBRF method.
> +	 */
> +	for (i = 0; i < obj->buffer.length && i < 8; i++)
> +		mask |= (u64)obj->buffer.pointer[i] << i * 8;
> +
> +	ACPI_FREE(obj);
> +
> +	if ((mask & BIT(WBRF_ENABLED)) && (mask & funcs) == funcs)
> +		return true;
> +
> +	return false;

You can directly return the condition's value, no need to wrap it into if.

> +}
> +
> +/**
> + * 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 = ACPI_COMPANION(dev);
> +
> +	if (!adev)
> +		return false;

Group call + its error handling together.

> +
> +	if (!acpi_amd_wbrf_supported_system())
> +		return false;
> +
> +	return check_acpi_wbrf(adev->handle,
> +			       WBRF_REVISION,
> +			       BIT(WBRF_RETRIEVE));

Fits one line.

> +}
> +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 acpi_device *adev = ACPI_COMPANION(dev);
> +	struct amd_wbrf_ranges_out acpi_out = {0};
> +	union acpi_object *obj;
> +	int ret = 0;
> +
> +	if (!adev)
> +		return -ENODEV;
> +
> +	obj = acpi_evaluate_wbrf(adev->handle,
> +				 WBRF_REVISION,
> +				 WBRF_RETRIEVE);

One line.

I'm now very confused what those constants actually mean, since you 
seem to sometimes use them with BIT() and sometimes not.

How can I know while reviewing each is done correctly? The only difference 
I can quickly pick up is "func" vs "funcs" in the argument name given 
to the function (which of course lacked documentation what it expects
to be given to it)?!?

> +	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) {

One line.

Use in_range().

> +		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);
> diff --git a/include/linux/acpi_amd_wbrf.h b/include/linux/acpi_amd_wbrf.h
> new file mode 100644
> index 000000000000..298779807312
> --- /dev/null
> +++ b/include/linux/acpi_amd_wbrf.h
> @@ -0,0 +1,101 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Wifi Band Exclusion Interface (AMD ACPI Implementation)
> + * Copyright (C) 2023 Advanced Micro Devices
> + */
> +
> +#ifndef _ACPI_AMD_WBRF_H
> +#define _ACPI_AMD_WBRF_H
> +
> +#include <linux/device.h>
> +#include <linux/notifier.h>
> +
> +/*
> + * The maximum number of frequency band ranges
> + */

No need to use multi-line comment.

> +#define MAX_NUM_OF_WBRF_RANGES		11
> +
> +/* Record actions */
> +#define WBRF_RECORD_ADD		0x0
> +#define WBRF_RECORD_REMOVE	0x1
> +
> +/*
> + * A freq_band_range is defined as a wifi frequency band with start
> + * and end frequency point specified(in Hz). And a valid range should

Lacking space.

> + * have its start and end frequency point filled with non-zero values.
> + * Meanwhile, the maximum number of wbrf ranges is limited as
> + * `MAX_NUM_OF_WBRF_RANGES`.

Use kerneldoc compatible syntax %MAX_NUM_OF_WBRF_RANGES instead (no need 
to mark it).

To me it seems with small effort, you could convert these into proper 
kerneldoc for both this and the next struct...

> + */
> +
> +struct freq_band_range {
> +	u64		start;
> +	u64		end;
> +};
> +
> +struct wbrf_ranges_in_out {
> +	u64			num_of_ranges;
> +	struct freq_band_range	band_list[MAX_NUM_OF_WBRF_RANGES];
> +};
> +
> +/*
> + * The notification types for the consumers are defined as below.
> + * The consumers may need to take different actions in response to
> + * different notifications.
> + * WBRF_CHANGED: there was some frequency band updates. The consumers
> + *               should retrieve the latest active frequency bands.

Make formatting compatible with kerneldoc.

> + */
> +enum wbrf_notifier_actions {
> +	WBRF_CHANGED,
> +};
> +
> +#if IS_ENABLED(CONFIG_AMD_WBRF)
> +bool acpi_amd_wbrf_supported_producer(struct device *dev);
> +int acpi_amd_wbrf_add_remove(struct device *dev, uint8_t action,
> +							struct wbrf_ranges_in_out *in);

Fix alignment.

> +bool acpi_amd_wbrf_supported_consumer(struct device *dev);
> +int amd_wbrf_retrieve_freq_band(struct device *dev,
> +				      struct wbrf_ranges_in_out *out);

Fix alignment.

Optionally, you could put these definitions on a single lines since 
they're <100 chars so that they'd have better greppablity.

> +int amd_wbrf_register_notifier(struct notifier_block *nb);
> +int amd_wbrf_unregister_notifier(struct notifier_block *nb);
> +#else
> +static inline
> +bool acpi_amd_wbrf_supported_consumer(struct device *dev)
> +{
> +	return false;
> +}
> +static inline
> +int acpi_amd_wbrf_remove_exclusion(struct device *dev,
> +				   struct wbrf_ranges_in_out *in)
> +{
> +	return -ENODEV;
> +}
> +static inline
> +int acpi_amd_wbrf_add_exclusion(struct device *dev,
> +				struct wbrf_ranges_in_out *in)
> +{
> +	return -ENODEV;
> +}
> +static inline
> +bool acpi_amd_wbrf_supported_producer(struct device *dev)
> +{
> +	return false;
> +}
> +static inline
> +int amd_wbrf_retrieve_freq_band(struct device *dev,
> +				      struct wbrf_ranges_in_out *out)

Another case of inconsistent alignment.

-- 
 i.

> +{
> +	return -ENODEV;
> +}
> +static inline
> +int amd_wbrf_register_notifier(struct notifier_block *nb)
> +{
> +	return -ENODEV;
> +}
> +static inline
> +int amd_wbrf_unregister_notifier(struct notifier_block *nb)
> +{
> +	return -ENODEV;
> +}
> +#endif /* CONFIG_AMD_WBRF */
> +
> +#endif /* _ACPI_AMD_WBRF_H */