linux-kernel - Re: [PATCH v14 2/9] platform/x86/amd: Add support for AMD ACPI based Wifi band RFI mitigation feature

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Message-ID: <67fe48be-8e10-47f7-bf47-e819ed02e732@amd.com>
Date:   Tue, 5 Dec 2023 15:22:07 +0800
From:   "Ma, Jun" <majun@....com>
To:     Hans de Goede <hdegoede@...hat.com>, Ma Jun <Jun.Ma2@....com>,
        amd-gfx@...ts.freedesktop.org, lenb@...nel.org,
        johannes@...solutions.net, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        alexander.deucher@....com, Lijo.Lazar@....com,
        mario.limonciello@....com, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, platform-driver-x86@...r.kernel.org
Cc:     majun@....com, Evan Quan <quanliangl@...mail.com>
Subject: Re: [PATCH v14 2/9] platform/x86/amd: Add support for AMD ACPI based
 Wifi band RFI mitigation feature

Hi Hans,

On 12/4/2023 9:00 PM, Hans de Goede wrote:
> Hi,
> 
> On 11/29/23 10:13, 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@...mail.com>
>> Signed-off-by: Evan Quan <quanliangl@...mail.com>
>> Signed-off-by: Ma Jun <Jun.Ma2@....com>
>>
>> --
>> v11:
>>  - fix typo(Simon)
>> v12:
>>  - Fix the code logic (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.
>> v13:
>>  - Fix the format issue (IIpo Jarvinen)
>>  - Add comment for some functions
>> v14:
>>  - Use the apci_check_dsm and acpi_evaluate_dsm (Hans de Goede)
> 
> Thank you this is much better.
> 
> I notice that the #define ACPI_AMD_WBRF_METHOD	"\\WBRF"
> still exists though and that this is still used in
> static bool acpi_amd_wbrf_supported_system(void).
> 
> I think it might be better to just remove
> these 2 all together.
> 
> Checking if a DSM with the expected GUID is present
> and if that has the correct bits set in its supported
> mask should be enough.
> 
> And on future systems the implementer may decide to
> not have a WBRF helper function at all and instead
> handle everything in the _DSM method.
> 
> So the "\\WBRF" check seems to be checking for
> what really is an implementation detail.
> 
Yes,you are right. I will fix these issues.
Thanks for your review and suggestion. 

Regards,
Ma Jun
> 2 other very small remark
> 
>> +/**
>> + * 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;
>> +
>> +	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);
> 
> Please don't use double empty lines, one empty line to separate things
> is enough.
> 
>> +
>> +/**
>> + * 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;
>> +
>> +	if (!acpi_amd_wbrf_supported_system())
>> +		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
> 
> You may go a bit over the 80 chars limit, please just make this
> a single line:
> 
>  * 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.
>> + */
> 
> Regards,
> 
> Hans
>