linux-kernel - Re: [PATCH V2 18/21] RISC-V: Add ACPI initialization in setup

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Date:   Fri, 24 Feb 2023 14:07:12 +0100
From:   Andrew Jones <ajones@...tanamicro.com>
To:     Sunil V L <sunilvl@...tanamicro.com>
Cc:     Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Conor Dooley <conor.dooley@...rochip.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Atish Patra <atishp@...osinc.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH V2 18/21] RISC-V: Add ACPI initialization in setup_arch()

On Fri, Feb 24, 2023 at 06:06:22PM +0530, Sunil V L wrote:
> On Mon, Feb 20, 2023 at 09:07:43PM +0100, Andrew Jones wrote:
> > On Thu, Feb 16, 2023 at 11:50:40PM +0530, Sunil V L wrote:
...
> > > +	fadt = (struct acpi_table_fadt *)table;
> > > +
> > > +	if (!(fadt->flags & ACPI_FADT_HW_REDUCED)) {
> > 
> > Do we also need to check for ACPI version 5.0+ when checking for HW
> > reduced?
> > 
> We need to add version check of FADT once spec is released. Will
> update it at that time.
> 

I was thinking we need the version check already just for the flag.
The spec has a footnote that says

"The description of HW_REDUCED_ACPI provided here applies to ACPI
 specifications 5.0 and later"

It doesn't really matter in practice since no RISC-V machines can
boot with ACPI less than a version that support the new RISC-V
tables... But I'd rather we either document that fact, or just do
the check.

Thanks,
drew