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

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Message-ID: <8d276868a0516f77864d1a1f41eeb0b091aced98.camel@intel.com>
Date:   Wed, 20 Jan 2021 19:18:02 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "Widawsky, Ben" <ben.widawsky@...el.com>,
        "Jonathan.Cameron@...wei.com" <Jonathan.Cameron@...wei.com>
CC:     "rdunlap@...radead.org" <rdunlap@...radead.org>,
        "hch@...radead.org" <hch@...radead.org>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>,
        "jcm@...masters.org" <jcm@...masters.org>,
        "linux-cxl@...r.kernel.org" <linux-cxl@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "helgaas@...nel.org" <helgaas@...nel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "daniel.lll@...baba-inc.com" <daniel.lll@...baba-inc.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "cbrowy@...ry-design.com" <cbrowy@...ry-design.com>,
        "Weiny, Ira" <ira.weiny@...el.com>
Subject: Re: [RFC PATCH v3 02/16] cxl/acpi: Add an acpi_cxl module for the CXL
 interconnect

On Tue, 2021-01-12 at 18:43 +0000, Jonathan Cameron 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.

Done.

> 
> > 
> > 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.

Dumping it from /sys/firmware/acpi/tables already works, but I did add
it to tables.c so it can also be overridden. I did this in a separate
patch, in case ACPI folks want to do this differently.

> 
> 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.
> 
> A few minor things inline

Agreed with all of your other comments below, and I've addresed them for
the next revision. Thanks for the review Jonathan!

> 
> Jonathan
> 
>