[Bug 217931] amd-pstate lacks crucial features: CPU frequency and boost control

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=217931

--- Comment #32 from Mario Limonciello (AMD) (mario.limonciello@amd.com) ---
> Apparently ryzenadj directly communicates with the SMU without using an
> in-tree kernel module to use an interface blessed by AMD, so that's highly
> unlikely to get support from them.
> Recommending reproducing the issue without using that at all first, it's
> going to keep on getting the blame until it's proven not to interfere.

Yes please do it without *anything* abusing that mailbox at all during the boot
(like ryzenadj or ryzen_smu).  It's entirely possible that another piece of
firmware fights over the same interfaces or data structures and that's part of
a problem.

It's also possible that attempts to read information using that tool
unintentionally causes information to also be written (as it's a reverse
engineered tool that uses an undocumented engineering interface anything is
possible)

The simpler the reproduce the better.

As I mentioned in the other issue, to rule out a kernel bug we may want to look
at the output of these MSRs while the issue happened.  If those are correct for
what has been programmed to scaling_max_freq, then we may be dealing with a
firmware bug.

#define MSR_AMD_CPPC_CAP1               0xc00102b0
#define MSR_AMD_CPPC_ENABLE             0xc00102b1
#define MSR_AMD_CPPC_CAP2               0xc00102b2
#define MSR_AMD_CPPC_REQ                0xc00102b3
#define MSR_AMD_CPPC_STATUS             0xc00102b4

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