On Wed, Jun 21, 2023 at 11:15:00AM -0500, Limonciello, Mario wrote: > > On 6/21/2023 10:39 AM, Johannes Berg wrote: > > On Wed, 2023-06-21 at 17:36 +0200, Andrew Lunn wrote: > > > On Wed, Jun 21, 2023 at 01:45:56PM +0800, Evan Quan wrote: > > > > From: Mario Limonciello <mario.limonciello@xxxxxxx> > > > > > > > > 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. > > > Do only ACPI based systems have: > > > > > > interference of relatively high-powered harmonics of the (G-)DDR > > > memory clocks with local radio module frequency bands used by > > > Wifi 6/6e/7." > > > > > > Could Device Tree based systems not experience this problem? > > They could, of course, but they'd need some other driver to change > > _something_ in the system? I don't even know what this is doing > > precisely under the hood in the ACPI BIOS, perhaps it adjusts the DDR > > memory clock frequency in response to WiFi using a frequency that will > > cause interference with harmonics. > > The way that WBRF has been architected, it's intended to be able > to scale to any type of device pair that has harmonic issues. So you set out to make something generic... > In the first use (Wifi 6e + specific AMD dGPUs) that matches this > series BIOS has the following purposes: > > 1) The existence of _DSM indicates that the system may not have > adequate shielding and should be using these mitigations. > > 2) Notification mechanism of frequency use. > > For the first problematic devices we *could* have done notifications > entirely in native Linux kernel code with notifier chains. > However that still means you need a hint from the platform that the > functionality is needed like a _DSD bit. > > It's also done this way so that AML could do some of the notifications > directly to applicable devices in the future without needing "consumer" > driver participation. And then tie is very closely to ACPI. Now, you are AMD, i get that ACPI is what you have. But i think as kernel Maintainers, we need to consider that ACPI is not the only thing used. Do we want the APIs to be agnostic? I think APIs used by drivers should be agnostic. Andrew