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Date:   Mon, 3 Jul 2023 22:53:26 -0500
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Subject: Re: [PATCH V5 1/9] drivers core: Add support for Wifi band RF
 mitigations
To:     "Quan, Evan" <Evan.Quan@amd.com>,
        "rafael@kernel.org" <rafael@kernel.org>,
        "lenb@kernel.org" <lenb@kernel.org>,
        "Deucher, Alexander" <Alexander.Deucher@amd.com>,
        "Koenig, Christian" <Christian.Koenig@amd.com>,
        "Pan, Xinhui" <Xinhui.Pan@amd.com>,
        "airlied@gmail.com" <airlied@gmail.com>,
        "daniel@ffwll.ch" <daniel@ffwll.ch>,
        "johannes@sipsolutions.net" <johannes@sipsolutions.net>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "edumazet@google.com" <edumazet@google.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "mdaenzer@redhat.com" <mdaenzer@redhat.com>,
        "maarten.lankhorst@linux.intel.com" 
        <maarten.lankhorst@linux.intel.com>,
        "tzimmermann@suse.de" <tzimmermann@suse.de>,
        "hdegoede@redhat.com" <hdegoede@redhat.com>,
        "jingyuwang_vip@163.com" <jingyuwang_vip@163.com>,
        "Lazar, Lijo" <Lijo.Lazar@amd.com>,
        "jim.cromie@gmail.com" <jim.cromie@gmail.com>,
        "bellosilicio@gmail.com" <bellosilicio@gmail.com>,
        "andrealmeid@igalia.com" <andrealmeid@igalia.com>,
        "trix@redhat.com" <trix@redhat.com>,
        "jsg@jsg.id.au" <jsg@jsg.id.au>, "arnd@arndb.de" <arnd@arndb.de>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>
References: <20230630103240.1557100-1-evan.quan@amd.com>
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From:   Mario Limonciello <mario.limonciello@amd.com>
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On 7/3/23 22:40, Quan, Evan wrote:
> [AMD Official Use Only - General]
> 
>> -----Original Message-----
>> From: Limonciello, Mario <Mario.Limonciello@amd.com>
>> Sent: Saturday, July 1, 2023 12:41 AM
>> To: Quan, Evan <Evan.Quan@amd.com>; rafael@kernel.org; lenb@kernel.org;
>> Deucher, Alexander <Alexander.Deucher@amd.com>; Koenig, Christian
>> <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>;
>> airlied@gmail.com; daniel@ffwll.ch; johannes@sipsolutions.net;
>> davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
>> pabeni@redhat.com; mdaenzer@redhat.com;
>> maarten.lankhorst@linux.intel.com; tzimmermann@suse.de;
>> hdegoede@redhat.com; jingyuwang_vip@163.com; Lazar, Lijo
>> <Lijo.Lazar@amd.com>; jim.cromie@gmail.com; bellosilicio@gmail.com;
>> andrealmeid@igalia.com; trix@redhat.com; jsg@jsg.id.au; arnd@arndb.de
>> 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; netdev@vger.kernel.org
>> 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@amd.com>
>>> 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>
>>> --
>>> 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?

That's fine, thanks.

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