Re: [RFC PATCH v3 02/16] cxl/acpi: Add an acpi_cxl module for the CXL interconnect

[Verma, Vishal L]

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@xxxxxxxxx> wrote:
> 
> > From: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> > 
> > 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@xxxxxxxxx>
> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
> > Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
> 
> 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
> 
>