RE: [PATCH V5 1/9] drivers core: Add support for Wifi band RF mitigations

From: Quan, Evan
Date: Mon Jul 03 2023 - 23:40:27 EST

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[AMD Official Use Only - General]

> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Saturday, July 1, 2023 12:41 AM
> To: Quan, Evan <Evan.Quan@xxxxxxx>; rafael@xxxxxxxxxx; lenb@xxxxxxxxxx;
> Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian
> <Christian.Koenig@xxxxxxx>; Pan, Xinhui <Xinhui.Pan@xxxxxxx>;
> airlied@xxxxxxxxx; daniel@xxxxxxxx; johannes@xxxxxxxxxxxxxxxx;
> davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; mdaenzer@xxxxxxxxxx;
> maarten.lankhorst@xxxxxxxxxxxxxxx; tzimmermann@xxxxxxx;
> hdegoede@xxxxxxxxxx; jingyuwang_vip@xxxxxxx; Lazar, Lijo
> <Lijo.Lazar@xxxxxxx>; jim.cromie@xxxxxxxxx; bellosilicio@xxxxxxxxx;
> andrealmeid@xxxxxxxxxx; trix@xxxxxxxxxx; jsg@xxxxxxxxx; arnd@xxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; amd-
> gfx@xxxxxxxxxxxxxxxxxxxxx; dri-devel@xxxxxxxxxxxxxxxxxxxxx; linux-
> wireless@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH V5 1/9] drivers core: Add support for Wifi band RF
> mitigations
>
> On 6/30/2023 05:32, Evan Quan 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.
> >
> > 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.
> >
> > Co-developed-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > Co-developed-by: Evan Quan <evan.quan@xxxxxxx>
> > Signed-off-by: Evan Quan <evan.quan@xxxxxxx>
> > --
> > v4->v5:
> > - promote this to be a more generic solution with input argument taking
> > `struct device` and provide better scalability to support non-ACPI
> > scenarios(Andrew)
> > - update the APIs naming and some other minor fixes(Rafael)
> > ---
> > drivers/base/Kconfig | 8 ++
> > drivers/base/Makefile | 1 +
> > drivers/base/wbrf.c | 227
> ++++++++++++++++++++++++++++++++++++++++++
> > include/linux/wbrf.h | 65 ++++++++++++
> > 4 files changed, 301 insertions(+)
> > create mode 100644 drivers/base/wbrf.c
> > create mode 100644 include/linux/wbrf.h
> >
> > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index
> > 2b8fd6bb7da0..5b441017b225 100644
> > --- a/drivers/base/Kconfig
> > +++ b/drivers/base/Kconfig
> > @@ -242,4 +242,12 @@ config FW_DEVLINK_SYNC_STATE_TIMEOUT
> > command line option on every system/board your kernel is expected
> to
> > work on.
> >
> > +config WBRF
> > + bool "Wifi band RF mitigation mechanism"
> > + default n
> > + 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.
> > +
> > endmenu
> > diff --git a/drivers/base/Makefile b/drivers/base/Makefile index
> > 3079bfe53d04..c844f68a6830 100644
> > --- a/drivers/base/Makefile
> > +++ b/drivers/base/Makefile
> > @@ -26,6 +26,7 @@ obj-$(CONFIG_GENERIC_MSI_IRQ) += platform-msi.o
> > obj-$(CONFIG_GENERIC_ARCH_TOPOLOGY) += arch_topology.o
> > obj-$(CONFIG_GENERIC_ARCH_NUMA) += arch_numa.o
> > obj-$(CONFIG_ACPI) += physical_location.o
> > +obj-$(CONFIG_WBRF) += wbrf.o
> >
> > obj-y += test/
> >
> > diff --git a/drivers/base/wbrf.c b/drivers/base/wbrf.c new file mode
> > 100644 index 000000000000..2163a8ec8a9a
> > --- /dev/null
> > +++ b/drivers/base/wbrf.c
> > @@ -0,0 +1,227 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Wifi Band Exclusion Interface
> > + * Copyright (C) 2023 Advanced Micro Devices
> > + *
> > + */
> > +
> > +#include <linux/wbrf.h>
> > +
> > +static BLOCKING_NOTIFIER_HEAD(wbrf_chain_head);
> > +static DEFINE_MUTEX(wbrf_mutex);
> > +static struct exclusion_range_pool wbrf_pool;
> > +
> > +static int _wbrf_add_exclusion_ranges(struct wbrf_ranges_in *in) {
> > + int i, j;
> > +
> > + for (i = 0; i < ARRAY_SIZE(in->band_list); i++) {
> > + if (!in->band_list[i].start &&
> > + !in->band_list[i].end)
> > + continue;
> > +
> > + for (j = 0; j < ARRAY_SIZE(wbrf_pool.band_list); j++) {
> > + if (wbrf_pool.band_list[j].start == in-
> >band_list[i].start &&
> > + wbrf_pool.band_list[j].end == in->band_list[i].end) {
> > + wbrf_pool.ref_counter[j]++;
> > + break;
> > + }
> > + }
> > + if (j < ARRAY_SIZE(wbrf_pool.band_list))
> > + continue;
> > +
> > + for (j = 0; j < ARRAY_SIZE(wbrf_pool.band_list); j++) {
> > + if (!wbrf_pool.band_list[j].start &&
> > + !wbrf_pool.band_list[j].end) {
> > + wbrf_pool.band_list[j].start = in-
> >band_list[i].start;
> > + wbrf_pool.band_list[j].end = in-
> >band_list[i].end;
> > + wbrf_pool.ref_counter[j] = 1;
> > + break;
> > + }
> > + }
> > + if (j >= ARRAY_SIZE(wbrf_pool.band_list))
> > + return -ENOSPC;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int _wbrf_remove_exclusion_ranges(struct wbrf_ranges_in *in) {
> > + int i, j;
> > +
> > + for (i = 0; i < ARRAY_SIZE(in->band_list); i++) {
> > + if (!in->band_list[i].start &&
> > + !in->band_list[i].end)
> > + continue;
> > +
> > + for (j = 0; j < ARRAY_SIZE(wbrf_pool.band_list); j++) {
> > + if (wbrf_pool.band_list[j].start == in-
> >band_list[i].start &&
> > + wbrf_pool.band_list[j].end == in->band_list[i].end) {
> > + wbrf_pool.ref_counter[j]--;
> > + if (!wbrf_pool.ref_counter[j]) {
> > + wbrf_pool.band_list[j].start = 0;
> > + wbrf_pool.band_list[j].end = 0;
> > + }
> > + break;
> > + }
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int _wbrf_retrieve_exclusion_ranges(struct wbrf_ranges_out
> > +*out) {
> > + int out_idx = 0;
> > + int i;
> > +
> > + memset(out, 0, sizeof(*out));
> > +
> > + for (i = 0; i < ARRAY_SIZE(wbrf_pool.band_list); i++) {
> > + if (!wbrf_pool.band_list[i].start &&
> > + !wbrf_pool.band_list[i].end)
> > + continue;
> > +
> > + out->band_list[out_idx].start = wbrf_pool.band_list[i].start;
> > + out->band_list[out_idx++].end = wbrf_pool.band_list[i].end;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * wbrf_supported_producer - Determine if the device can report
> > +frequencies
> > + *
> > + * @dev: device pointer
> > + *
> > + * WBRF is used to mitigate devices that cause harmonic interference.
> > + * This function will determine if this device needs to report such
> frequencies.
> > + */
> > +bool wbrf_supported_producer(struct device *dev) {
> > + return true;
> > +}
> > +EXPORT_SYMBOL_GPL(wbrf_supported_producer);
> > +
> > +/**
> > + * wbrf_add_exclusion - Add frequency ranges to the exclusion list
> > + *
> > + * @dev: device pointer
> > + * @in: input structure containing the frequency ranges to be added
> > + *
> > + * Add frequencies into the exclusion list for supported consumers
> > + * to react to.
> > + */
> > +int wbrf_add_exclusion(struct device *dev,
> > + struct wbrf_ranges_in *in)
> > +{
> > + int r;
> > +
> > + mutex_lock(&wbrf_mutex);
> > +
> > + r = _wbrf_add_exclusion_ranges(in);
> > +
> > + mutex_unlock(&wbrf_mutex);
> > + if (r)
> > + return r;
> > +
> > + blocking_notifier_call_chain(&wbrf_chain_head, WBRF_CHANGED,
> NULL);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(wbrf_add_exclusion);
> > +
> > +/**
> > + * wbrf_remove_exclusion - Remove frequency ranges from the exclusion
> > +list
> > + *
> > + * @dev: device pointer
> > + * @in: input structure containing the frequency ranges to be removed
> > + *
> > + * Remove frequencies from the exclusion list for supported consumers
> > + * to react to.
> > + */
> > +int wbrf_remove_exclusion(struct device *dev,
> > + struct wbrf_ranges_in *in)
> > +{
> > + int r;
> > +
> > + mutex_lock(&wbrf_mutex);
> > +
> > + r = _wbrf_remove_exclusion_ranges(in);
> > +
> > + mutex_unlock(&wbrf_mutex);
> > + if (r)
> > + return r;
> > +
> > + blocking_notifier_call_chain(&wbrf_chain_head, WBRF_CHANGED,
> NULL);
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(wbrf_remove_exclusion);
> > +
> > +/**
> > + * wbrf_supported_consumer - Determine if the device can react to
> > +frequencies
> > + *
> > + * @dev: device pointer
> > + *
> > + * WBRF is used to mitigate devices that cause harmonic interference.
> > + * This function will determine if this device needs to react to
> > +reports from
> > + * other devices for such frequencies.
> > + */
> > +bool wbrf_supported_consumer(struct device *dev) {
> > + return true;
> > +}
> > +EXPORT_SYMBOL_GPL(wbrf_supported_consumer);
> > +
> > +/**
> > + * wbrf_register_notifier - Register for notifications of frequency
> > +changes
> > + *
> > + * @nb: driver notifier block
> > + *
> > + * WBRF is used to mitigate devices that cause harmonic interference.
> > + * This function will allow consumers to register for frequency notifications.
> > + */
> > +int wbrf_register_notifier(struct notifier_block *nb) {
> > + return blocking_notifier_chain_register(&wbrf_chain_head, nb); }
> > +EXPORT_SYMBOL_GPL(wbrf_register_notifier);
> > +
> > +/**
> > + * wbrf_unregister_notifier - Unregister for notifications of
> > +frequency changes
> > + *
> > + * @nb: driver notifier block
> > + *
> > + * WBRF is used to mitigate devices that cause harmonic interference.
> > + * This function will allow consumers to unregister for frequency
> notifications.
> > + */
> > +int wbrf_unregister_notifier(struct notifier_block *nb) {
> > + return blocking_notifier_chain_unregister(&wbrf_chain_head, nb); }
> > +EXPORT_SYMBOL_GPL(wbrf_unregister_notifier);
> > +
> > +/**
> > + * wbrf_retrieve_exclusions - Retrieve the exclusion list
> > + *
> > + * @dev: device pointer
> > + * @out: output structure containing the frequency ranges to be
> > +excluded
> > + *
> > + * Retrieve the current exclusion list */ int
> > +wbrf_retrieve_exclusions(struct device *dev,
> > + struct wbrf_ranges_out *out)
> > +{
> > + int r;
> > +
> > + mutex_lock(&wbrf_mutex);
> > +
> > + r = _wbrf_retrieve_exclusion_ranges(out);
> > +
> > + mutex_unlock(&wbrf_mutex);
> > +
> > + return r;
> > +}
> > +EXPORT_SYMBOL_GPL(wbrf_retrieve_exclusions);
> > diff --git a/include/linux/wbrf.h b/include/linux/wbrf.h new file mode
> > 100644 index 000000000000..3ca95786cef5
> > --- /dev/null
> > +++ b/include/linux/wbrf.h
> > @@ -0,0 +1,65 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Wifi Band Exclusion Interface
> > + * Copyright (C) 2023 Advanced Micro Devices */
> > +
> > +#ifndef _LINUX_WBRF_H
> > +#define _LINUX_WBRF_H
> > +
> > +#include <linux/device.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 exclusion_range_pool {
> > + struct exclusion_range band_list[MAX_NUM_OF_WBRF_RANGES];
> > + uint64_t
> ref_counter[MAX_NUM_OF_WBRF_RANGES];
> > +};
> > +
> > +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];
> > +} __packed;
> > +
> > +enum wbrf_notifier_actions {
> > + WBRF_CHANGED,
> > +};
> > +
> > +#ifdef CONFIG_WBRF
> > +bool wbrf_supported_producer(struct device *dev); int
> > +wbrf_add_exclusion(struct device *adev,
> > + struct wbrf_ranges_in *in);
> > +int wbrf_remove_exclusion(struct device *dev,
> > + struct wbrf_ranges_in *in);
> > +int wbrf_retrieve_exclusions(struct device *dev,
> > + struct wbrf_ranges_out *out); bool
> > +wbrf_supported_consumer(struct device *dev);
> > +
> > +int wbrf_register_notifier(struct notifier_block *nb); int
> > +wbrf_unregister_notifier(struct notifier_block *nb); #else static
> > +inline bool wbrf_supported_producer(struct device *dev) { return
> > +false; } static inline int wbrf_add_exclusion(struct device *adev,
> > + struct wbrf_ranges_in *in) { return -
> ENODEV; } static inline
> > +int wbrf_remove_exclusion(struct device *dev,
> > + struct wbrf_ranges_in *in) { return -
> ENODEV; } static inline int
> > +wbrf_retrieve_exclusions(struct device *dev,
> > + struct wbrf_ranges_out *out)
> { return -ENODEV; } static
> > +inline bool wbrf_supported_consumer(struct device *dev) { return
> > +false; } static inline int wbrf_register_notifier(struct
> > +notifier_block *nb) { return -ENODEV; } static inline int
> > +wbrf_unregister_notifier(struct notifier_block *nb) { return -ENODEV;
> > +} #endif
> > +
>
> Right now there are stubs for non CONFIG_WBRF as well as other patches are
> using #ifdef CONFIG_WBRF or having their own stubs. Like mac80211 patch
> looks for #ifdef CONFIG_WBRF.
>
> I think we should pick one or the other.
Right..
>
> Having other subsystems #ifdef CONFIG_WBRF will make the series easier to
> land through multiple trees; so I have a slight leaning in that direction.
I kind of expecting to use the other way. That is to make CONFIG_WBRF agnostic to other subsystems or drivers.
They (other subsystems or drivers) can always assume those wbrf_xxxxx interfaces are available.
What they need to care only are the return values of those interfaces.
How do you think?

Evan
>
> > +#endif /* _LINUX_WBRF_H */

Next message: Quan, Evan: "RE: [PATCH V5 1/9] drivers core: Add support for Wifi band RF mitigations"
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In reply to: Mario Limonciello: "Re: [PATCH V5 1/9] drivers core: Add support for Wifi band RF mitigations"
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