Hi llpo, Thanks for these comments on format issues, I'll fix it in the next version. Regards, Ma Jun On 10/17/2023 5:20 PM, Ilpo Järvinen wrote: > On Tue, 17 Oct 2023, Ma Jun wrote: > >> Add documentation about AMD's Wifi band RFI mitigation (WBRF) mechanism >> explaining the theory and how it is used. >> >> Signed-off-by: Ma Jun <Jun.Ma2@xxxxxxx> >> --- >> Documentation/driver-api/wbrf.rst | 73 +++++++++++++++++++++++++++++++ >> 1 file changed, 73 insertions(+) >> create mode 100644 Documentation/driver-api/wbrf.rst >> >> diff --git a/Documentation/driver-api/wbrf.rst b/Documentation/driver-api/wbrf.rst >> new file mode 100644 >> index 000000000000..8561840263b3 >> --- /dev/null >> +++ b/Documentation/driver-api/wbrf.rst >> @@ -0,0 +1,73 @@ >> +.. SPDX-License-Identifier: GPL-2.0-or-later >> + >> +================================= >> +WBRF - Wifi Band RFI Mitigations >> +================================= >> +Due to electrical and mechanical constraints in certain platform designs > > Add empty line before starting the content of a section. > >> +there may be likely interference of relatively high-powered harmonics of >> +the GPU memory clocks with local radio module frequency bands used by >> +certain Wifi bands. >> + >> +To mitigate possible RFI interference producers can advertise the >> +frequencies in use and consumers can use this information to avoid using >> +these frequencies for sensitive features. >> + >> +When a platform is known to have this issue with any contained devices, >> +the platform designer will advertise the availability of this feature via >> +ACPI devices with a device specific method (_DSM). >> +* Producers with this _DSM will be able to advertise the frequencies in use. >> +* Consumers with this _DSM will be able to register for notifications of >> +frequencies in use. >> + >> +Some general terms >> +================== >> +Producer: such component who can produce high-powered radio frequency >> +Consumer: such component who can adjust its in-use frequency in >> + response to the radio frequencies of other components to >> + mitigate the possible RFI. >> + >> +To make the mechanism function, those producers should notify active use >> +of their particular frequencies so that other consumers can make relative >> +internal adjustments as necessary to avoid this resonance. >> + >> +ACPI interface >> +============== >> +Although initially used by for wifi + dGPU use cases, the ACPI interface >> +can be scaled to any type of device that a platform designer discovers >> +can cause interference. >> + >> +The GUID used for the _DSM is 7B7656CF-DC3D-4C1C-83E9-66E721DE3070. >> + >> +3 functions are available in this _DSM: >> + >> +* 0: discover # of functions available >> +* 1: record RF bands in use >> +* 2: retrieve RF bands in use >> + >> +Driver programming interface >> +============================ >> +.. kernel-doc:: drivers/platform/x86/amd/wbrf.c >> + >> +Sample Usage >> +============= >> +The expected flow for the producers: >> +1) During probe, call `acpi_amd_wbrf_supported_producer` to check if WBRF >> +can be enabled for the device. >> +2) On using some frequency band, call `acpi_amd_wbrf_add_remove` with 'add' >> +param to get other consumers properly notified. >> +3) Or on stopping using some frequency band, call >> +`acpi_amd_wbrf_add_remove` with 'remove' param to get other consumers notified. >> + >> +The expected flow for the consumers: >> +1) During probe, call `acpi_amd_wbrf_supported_consumer` to check if WBRF >> +can be enabled for the device. >> +2) Call `amd_wbrf_register_notifier` to register for notification >> +of frequency band change(add or remove) from other producers. >> +3) Call the `amd_wbrf_retrieve_freq_band` intentionally to retrieve >> +current active frequency bands considering some producers may broadcast >> +such information before the consumer is up. >> +4) On receiving a notification for frequency band change, run >> +`amd_wbrf_retrieve_freq_band` again to retrieve the latest >> +active frequency bands. >> +5) During driver cleanup, call `amd_wbrf_unregister_notifier` to >> +unregister the notifier. > > Align these so that only the numbers start from first column. I think the > proper markup for numbered lists is 1. not 1). > >
