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Date:   Sun, 18 Jun 2023 21:04:29 -0500
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Subject: Re: [PATCH V3 1/7] drivers/acpi: Add support for Wifi band RF
 mitigations
Content-Language: en-US
To:     Evan Quan <evan.quan@amd.com>
Cc:     linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-wireless@vger.kernel.org, rafael@kernel.org, lenb@kernel.org,
        Alexander.Deucher@amd.com, Christian.Koenig@amd.com,
        Xinhui.Pan@amd.com, airlied@gmail.com, daniel@ffwll.ch,
        kvalo@kernel.org, nbd@nbd.name, lorenzo@kernel.org,
        ryder.lee@mediatek.com, shayne.chen@mediatek.com,
        sean.wang@mediatek.com, matthias.bgg@gmail.com,
        angelogioacchino.delregno@collabora.com, Lijo.Lazar@amd.com
References: <20230616065757.1054422-1-evan.quan@amd.com>
 <20230616065757.1054422-2-evan.quan@amd.com>
From:   Mario Limonciello <mario.limonciello@amd.com>
In-Reply-To: <20230616065757.1054422-2-evan.quan@amd.com>
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On 6/16/23 01:57, Evan Quan wrote:
> From: Mario Limonciello <mario.limonciello@amd.com>
> 
> 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 an ACPI based mechanism that
> devices can use to notify active use of particular frequencies so
> that devices can make relative internal adjustments as necessary
> to avoid this resonance.
> 
> In order for a device to support this, the expected flow for device
> driver or subsystems:
> 
> Drivers/subsystems contributing frequencies:
> 
> 1) During probe, check `wbrf_supported_producer` to see if WBRF supported
>     for the device.
> 2) If adding frequencies, then call `wbrf_add_exclusion` with the
>     start and end ranges of the frequencies.
> 3) If removing frequencies, then call `wbrf_remove_exclusion` with
>     start and end ranges of the frequencies.
> 
> Drivers/subsystems responding to frequencies:
> 
> 1) During probe, check `wbrf_supported_consumer` to see if WBRF is supported
>     for the device.
> 2) Call the `wbrf_retrieve_exclusions` to retrieve the current
>     exclusions on receiving an ACPI notification for a new frequency
>     change.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> Co-developed-by: Evan Quan <evan.quan@amd.com>
> Signed-off-by: Evan Quan <evan.quan@amd.com>
> --
> v1->v2:
>    - move those wlan specific implementations to net/mac80211(Mario)
> ---
>   drivers/acpi/Kconfig     |   7 ++
>   drivers/acpi/Makefile    |   2 +
>   drivers/acpi/acpi_wbrf.c | 215 +++++++++++++++++++++++++++++++++++++++
>   include/linux/wbrf.h     |  55 ++++++++++
>   4 files changed, 279 insertions(+)
>   create mode 100644 drivers/acpi/acpi_wbrf.c
>   create mode 100644 include/linux/wbrf.h
> 
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index ccbeab9500ec..9ee7c7dcc3e6 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -611,3 +611,10 @@ config X86_PM_TIMER
>   
>   	  You should nearly always say Y here because many modern
>   	  systems require this timer.
> +
> +config ACPI_WBRF
> +	bool "ACPI Wifi band RF mitigation mechanism"
> +	help
> +	  Wifi band RF mitigation mechanism allows multiple drivers from
> +	  different domains to notify the frequencies in use so that hardware
> +	  can be reconfigured to avoid harmonic conflicts.
> \ No newline at end of file

There should be a newline at the end of the Kconfig file.

> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index feb36c0b9446..be173e76aa62 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -131,3 +131,5 @@ obj-y				+= dptf/
>   obj-$(CONFIG_ARM64)		+= arm64/
>   
>   obj-$(CONFIG_ACPI_VIOT)		+= viot.o
> +
> +obj-$(CONFIG_ACPI_WBRF)		+= acpi_wbrf.o
> \ No newline at end of file
> diff --git a/drivers/acpi/acpi_wbrf.c b/drivers/acpi/acpi_wbrf.c
> new file mode 100644
> index 000000000000..8c275998ac29
> --- /dev/null
> +++ b/drivers/acpi/acpi_wbrf.c
> @@ -0,0 +1,215 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * AMD Wifi Band Exclusion Interface
> + * Copyright (C) 2023 Advanced Micro Devices
> + *
> + */
> +
> +#include <linux/wbrf.h>
> +
> +/* functions */
> +#define WBRF_RECORD		0x1
> +#define WBRF_RETRIEVE		0x2
> +
> +/* record actions */
> +#define WBRF_RECORD_ADD		0x0
> +#define WBRF_RECORD_REMOVE	0x1
> +
> +#define WBRF_REVISION		0x1
> +
> +static const guid_t wifi_acpi_dsm_guid =
> +	GUID_INIT(0x7b7656cf, 0xdc3d, 0x4c1c,
> +		  0x83, 0xe9, 0x66, 0xe7, 0x21, 0xde, 0x30, 0x70);
> +
> +static int wbrf_dsm(struct acpi_device *adev, u8 fn,
> +		    union acpi_object *argv4,
> +		    union acpi_object **out)
> +{
> +	union acpi_object *obj;
> +	int rc;
> +
> +	obj = acpi_evaluate_dsm(adev->handle, &wifi_acpi_dsm_guid,
> +				WBRF_REVISION, fn, argv4);
> +	if (!obj)
> +		return -ENXIO;
> +
> +	switch (obj->type) {
> +	case ACPI_TYPE_BUFFER:
> +		if (!*out) {
> +			rc = -EINVAL;
> +			break;
> +		}
> +		*out = obj;
> +		return 0;
> +
> +	case ACPI_TYPE_INTEGER:
> +		rc =  obj->integer.value ? -EINVAL : 0;
> +		break;
> +	default:
> +		rc = -EOPNOTSUPP;
> +	}
> +	ACPI_FREE(obj);
> +
> +	return rc;
> +}
> +
> +static int wbrf_record(struct acpi_device *adev, uint8_t action,
> +		       struct wbrf_ranges_in *in)
> +{
> +	union acpi_object *argv4;
> +	uint32_t num_of_ranges = 0;
> +	uint32_t arg_idx = 0;
> +	uint32_t loop_idx;
> +	int ret;
> +
> +	if (!in)
> +		return -EINVAL;
> +
> +	for (loop_idx = 0; loop_idx < ARRAY_SIZE(in->band_list);
> +	     loop_idx++)
> +		if (in->band_list[loop_idx].start &&
> +		    in->band_list[loop_idx].end)
> +			num_of_ranges++;
> +
> +	argv4 = kzalloc(sizeof(*argv4) * (2 * num_of_ranges + 2 + 1), GFP_KERNEL);
> +	if (!argv4)
> +		return -ENOMEM;
> +
> +	argv4[arg_idx].package.type = ACPI_TYPE_PACKAGE;
> +	argv4[arg_idx].package.count = 2 + 2 * num_of_ranges;
> +	argv4[arg_idx++].package.elements = &argv4[1];
> +	argv4[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +	argv4[arg_idx++].integer.value = num_of_ranges;
> +	argv4[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +	argv4[arg_idx++].integer.value = action;
> +
> +	for (loop_idx = 0; loop_idx < ARRAY_SIZE(in->band_list);
> +	     loop_idx++) {
> +		if (!in->band_list[loop_idx].start ||
> +		    !in->band_list[loop_idx].end)
> +			continue;
> +
> +		argv4[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +		argv4[arg_idx++].integer.value = in->band_list[loop_idx].start;
> +		argv4[arg_idx].integer.type = ACPI_TYPE_INTEGER;
> +		argv4[arg_idx++].integer.value = in->band_list[loop_idx].end;
> +	}
> +
> +	ret = wbrf_dsm(adev, WBRF_RECORD, argv4, NULL);
> +
> +	kfree(argv4);
> +
> +	return ret;
> +}
> +
> +int wbrf_add_exclusion(struct acpi_device *adev,
> +		       struct wbrf_ranges_in *in)
> +{
> +	return wbrf_record(adev, WBRF_RECORD_ADD, in);
> +}
> +EXPORT_SYMBOL_GPL(wbrf_add_exclusion);
> +
> +int wbrf_remove_exclusion(struct acpi_device *adev,
> +			  struct wbrf_ranges_in *in)
> +{
> +	return wbrf_record(adev, WBRF_RECORD_REMOVE, in);
> +}
> +EXPORT_SYMBOL_GPL(wbrf_remove_exclusion);
> +
> +bool wbrf_supported_producer(struct acpi_device *adev)
> +{
> +	return acpi_check_dsm(adev->handle, &wifi_acpi_dsm_guid,
> +			      WBRF_REVISION,
> +			      (1ULL << WBRF_RECORD) | (1ULL << WBRF_RETRIEVE));
> +}
> +EXPORT_SYMBOL_GPL(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_SUCCESS(ret))
> +		return (union acpi_object *)buf.pointer;
> +
> +	if (ret != AE_NOT_FOUND)
> +		acpi_handle_warn(handle,
> +				 "failed to evaluate WBRF(0x%x)\n", ret);
> +
> +	return NULL;
> +}
> +
> +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;
> +
> +	for (i = 0; i < obj->buffer.length && i < 8; i++)
> +		mask |= (((u64)obj->buffer.pointer[i]) << (i * 8));
> +	ACPI_FREE(obj);
> +
> +	/*
> +	 * Bit 0 indicates whether there's support for any functions other than
> +	 * function 0.
> +	 */
> +	if ((mask & 0x1) && (mask & funcs) == funcs)
> +		return true;
> +
> +	return false;
> +}
> +
> +bool wbrf_supported_consumer(struct acpi_device *adev)
> +{
> +	return check_acpi_wbrf(adev->handle,
> +			       WBRF_REVISION,
> +			       1ULL << WBRF_RETRIEVE);
> +}
> +EXPORT_SYMBOL_GPL(wbrf_supported_consumer);
> +
> +int wbrf_retrieve_exclusions(struct acpi_device *adev,
> +			     struct wbrf_ranges_out *exclusions_out)
> +{
> +	union acpi_object *obj;
> +
> +	obj = acpi_evaluate_wbrf(adev->handle,
> +				 WBRF_REVISION,
> +				 WBRF_RETRIEVE);
> +	if (!obj)
> +		return -EINVAL;
> +
> +	memcpy(exclusions_out, obj->buffer.pointer, obj->buffer.length);
> +
> +	ACPI_FREE(obj);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(wbrf_retrieve_exclusions);
> diff --git a/include/linux/wbrf.h b/include/linux/wbrf.h
> new file mode 100644
> index 000000000000..e4c99b69f1d2
> --- /dev/null
> +++ b/include/linux/wbrf.h
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * AMD Wifi Band Exclusion Interface
> + * Copyright (C) 2023 Advanced Micro Devices
> + */
> +
> +#ifndef _LINUX_WBRF_H
> +#define _LINUX_WBRF_H
> +
> +#include <linux/acpi.h>
> +
> +/* Maximum number of wbrf ranges */
> +#define MAX_NUM_OF_WBRF_RANGES		11 > +
> +struct exclusion_range {
> +	/* start and end point of the frequency range in Hz */
> +	uint64_t	start;
> +	uint64_t	end;
> +};
> +
> +struct wbrf_ranges_in {
> +	/* valid entry: `start` and `end` filled with non-zero values */
> +	struct exclusion_range	band_list[MAX_NUM_OF_WBRF_RANGES];
> +};
> +
> +struct wbrf_ranges_out {
> +	uint32_t		num_of_ranges;
> +	struct exclusion_range	band_list[MAX_NUM_OF_WBRF_RANGES];
> +} __attribute__((packed));
> +
> +/**
> + * APIs needed by drivers/subsystems for contributing frequencies:
> + * During probe, check `wbrf_supported_producer` to see if WBRF is supported.
> + * If adding frequencies, then call `wbrf_add_exclusion` with the
> + * start and end points specified for the frequency ranges added.
> + * If removing frequencies, then call `wbrf_remove_exclusion` with
> + * start and end points specified for the frequency ranges added.
> + */
> +bool wbrf_supported_producer(struct acpi_device *adev);
> +int wbrf_add_exclusion(struct acpi_device *adev,
> +		       struct wbrf_ranges_in *in);
> +int wbrf_remove_exclusion(struct acpi_device *adev,
> +			  struct wbrf_ranges_in *in);
> +
> +/**
> + * APIs needed by drivers/subsystems responding to frequencies:
> + * During probe, check `wbrf_supported_consumer` to see if WBRF is supported.
> + * When receiving an ACPI notification for some frequencies change, run
> + * `wbrf_retrieve_exclusions` to retrieve the latest frequencies ranges.
> + */
> +int wbrf_retrieve_exclusions(struct acpi_device *adev,
> +			     struct wbrf_ranges_out *out);
> +bool wbrf_supported_consumer(struct acpi_device *adev);
> +
> +#endif /* _LINUX_WBRF_H */