linux-kernel - Re: [PATCH] Thermal: intel: hfi: Give HFI instances package scope

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Message-ID: <20240709021917.GA1891@ranerica-svr.sc.intel.com>
Date: Mon, 8 Jul 2024 19:19:17 -0700
From: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Zhang Rui <rui.zhang@...el.com>, rafael.j.wysocki@...el.com,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH] Thermal: intel: hfi: Give HFI instances package scope

On Wed, Jul 03, 2024 at 01:33:03PM +0200, Rafael J. Wysocki wrote:
> On Wed, Jul 3, 2024 at 7:55 AM Zhang Rui <rui.zhang@...el.com> wrote:
> >
> > The Intel Software Developer's Manual defines the scope of HFI (registers
> > and memory buffer) as package. Use package scope* in the software
> 
> "as a package"
> 
> > representation of an HFI instance.
> >
> > Using die scope in HFI instances has the effect of creating multiple,
> > conflicting, instances for the same package: each instance allocates its
> > own memory buffer and configures the same package-level registers.
> > Specifically, only one of the allocated memory buffers can be set in the
> > MSR_IA32_HW_FEEDBACK_PTR register. CPUs get incorrect HFI data from the
> > table.
> >
> > The problem does not affect current HFI-capable platforms because they
> > all have single-die processors.
> >
> > * We used die scope for HFI instances because there have been processors
> > in which packages where enumerated as dies. None of those systems support
> 
> "were"
> 
> > HFI. If such a system emerged we would need to quirk it.
> >
> > Co-developed-by: Chen Yu <yu.c.chen@...el.com>
> > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> > Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> 
> Ricardo, any concerns?

No concerns. IMO, it is important to document why we were using die scope
before. Rui has done it.

This patch looks good to me.

FWIW, Reviewed-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>