linux-kernel - RE: [RFC PATCH v3 02/16] cxl/acpi: Add an acpi

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Date:   Wed, 13 Jan 2021 17:55:04 +0000
From:   "Kaneda, Erik" <erik.kaneda@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "Widawsky, Ben" <ben.widawsky@...el.com>
CC:     "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "Verma, Vishal L" <vishal.l.verma@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        "Weiny, Ira" <ira.weiny@...el.com>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Jon Masters <jcm@...masters.org>,
        "Chris Browy" <cbrowy@...ry-design.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Christoph Hellwig <hch@...radead.org>,
        "daniel.lll@...baba-inc.com" <daniel.lll@...baba-inc.com>,
        "Moore, Robert" <robert.moore@...el.com>
Subject: RE: [RFC PATCH v3 02/16] cxl/acpi: Add an acpi_cxl module for the CXL
 interconnect



> -----Original Message-----
> From: Dan Williams <dan.j.williams@...el.com>
> Sent: Tuesday, January 12, 2021 11:44 AM
> To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Cc: Widawsky, Ben <ben.widawsky@...el.com>; linux-cxl@...r.kernel.org;
> Verma, Vishal L <vishal.l.verma@...el.com>; Linux Kernel Mailing List <linux-
> kernel@...r.kernel.org>; Linux PCI <linux-pci@...r.kernel.org>; Weiny, Ira
> <ira.weiny@...el.com>; Kelley, Sean V <sean.v.kelley@...el.com>; Wysocki,
> Rafael J <rafael.j.wysocki@...el.com>; Bjorn Helgaas <helgaas@...nel.org>;
> Jon Masters <jcm@...masters.org>; Chris Browy <cbrowy@...ry-
> design.com>; Randy Dunlap <rdunlap@...radead.org>; Christoph Hellwig
> <hch@...radead.org>; daniel.lll@...baba-inc.com; Moore, Robert
> <robert.moore@...el.com>; Kaneda, Erik <erik.kaneda@...el.com>
> Subject: Re: [RFC PATCH v3 02/16] cxl/acpi: Add an acpi_cxl module for the
> CXL interconnect
> 
> On Tue, Jan 12, 2021 at 10:44 AM Jonathan Cameron
> <Jonathan.Cameron@...wei.com> wrote:
> >
> > On Mon, 11 Jan 2021 14:51:06 -0800
> > Ben Widawsky <ben.widawsky@...el.com> wrote:
> >
> > > From: Vishal Verma <vishal.l.verma@...el.com>
> > >
> > > Add an acpi_cxl module to coordinate the ACPI portions of the CXL
> > > (Compute eXpress Link) interconnect. This driver binds to ACPI0017
> > > objects in the ACPI tree, and coordinates access to the resources
> > > provided by the ACPI CEDT (CXL Early Discovery Table).
> > >
> > > It also coordinates operations of the root port _OSC object to notify
> > > platform firmware that the OS has native support for the CXL
> > > capabilities of endpoints.
> > >
> > > Note: the actbl1.h changes are speculative. The expectation is that they
> > > will arrive through the ACPICA tree in due time.
> >
> > I would pull the ACPICA changes out into a precursor patch.
> 
> 
> >
> > >
> > > Cc: Ben Widawsky <ben.widawsky@...el.com>
> > > Cc: Dan Williams <dan.j.williams@...el.com>
> > > Signed-off-by: Vishal Verma <vishal.l.verma@...el.com>
> > > Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> >
> > Hi,
> >
> > I think it would be good to also add CEDT to the list in drivers/acpi/tables.c
> > so that we can dump it from /sys/firmware/acpi/tables/ and potentially
> > override it from an initrd.
> 
> ACPICA changes will eventually come through the ACPI tree not this patch
> set.
> 
> 
> >
> > https://elixir.bootlin.com/linux/v5.11-
> rc3/source/drivers/acpi/tables.c#L482
> > Can be very helpful whilst debugging.  Related to that, anyone know if
> anyone
> > has acpica patches so we can have iasl -d work on the table?  Would
> probably
> > be useful but I'd rather not duplicate work if it's already done.
> >
> 
> The supplemental tables described here:
> 
> https://www.uefi.org/acpi
> 
> ...do eventually make there way into ACPICA. Added Bob and Erik in
> case they can comment on when CEDT and CDAT support will be picked up.

We would be happy to add support. I think Ben has reached out to me earlier about something like this but I haven’t had a chance to implement... Sorry about the delay.. How soon is the iASL/ACPICA support needed for CDAT and CDET?

Erik