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Date: Tue, 12 Jan 2021 16:09:44 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Ben Widawsky <ben.widawsky@...el.com>
Cc: linux-cxl@...r.kernel.org, Vishal Verma <vishal.l.verma@...el.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux PCI <linux-pci@...r.kernel.org>,
"linux-acpi@...r.kernel.org, Ira Weiny" <ira.weiny@...el.com>,
Dan Williams <dan.j.williams@...el.com>,
"Kelley, Sean V" <sean.v.kelley@...el.com>,
Rafael Wysocki <rafael.j.wysocki@...el.com>,
Bjorn Helgaas <helgaas@...nel.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
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
Subject: Re: [RFC PATCH v3 03/16] cxl/acpi: add OSC support
Something has gone wrong with CCing this to linux-acpi, but no worries.
On Tue, Jan 12, 2021 at 1:29 AM Ben Widawsky <ben.widawsky@...el.com> wrote:
>
> From: Vishal Verma <vishal.l.verma@...el.com>
>
> Add support to advertise OS capabilities, and request OS control for CXL
> features using the ACPI _OSC mechanism. Advertise support for all
> possible CXL features, and attempt to request control for all possible
> features.
>
> Based on a patch by Sean Kelley.
>
> Signed-off-by: Vishal Verma <vishal.l.verma@...el.com>
> Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> ---
> Documentation/cxl/memory-devices.rst | 15 ++
> drivers/cxl/acpi.c | 260 ++++++++++++++++++++++++++-
> drivers/cxl/acpi.h | 20 +++
> 3 files changed, 292 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/cxl/memory-devices.rst b/Documentation/cxl/memory-devices.rst
> index aa4262280c67..6ce88f9d5f4f 100644
> --- a/Documentation/cxl/memory-devices.rst
> +++ b/Documentation/cxl/memory-devices.rst
> @@ -13,3 +13,18 @@ Driver Infrastructure
> =====================
>
> This sections covers the driver infrastructure for a CXL memory device.
> +
> +ACPI CXL
> +--------
> +
> +.. kernel-doc:: drivers/cxl/acpi.c
> + :doc: cxl acpi
> +
> +.. kernel-doc:: drivers/cxl/acpi.c
> + :internal:
> +
> +External Interfaces
> +===================
> +
> +.. kernel-doc:: drivers/cxl/acpi.c
> + :export:
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> index 0f1ba9b3f1ed..af9c0dfdee20 100644
> --- a/drivers/cxl/acpi.c
> +++ b/drivers/cxl/acpi.c
> @@ -11,7 +11,258 @@
> #include <linux/pci.h>
> #include "acpi.h"
>
> -/*
> +/**
> + * DOC: cxl acpi
> + *
> + * ACPI _OSC setup: The exported function cxl_bus_acquire() sets up ACPI
> + * Operating System Capabilities (_OSC) for the CXL bus. It declares support
> + * for all CXL capabilities, and attempts to request control for all possible
> + * capabilities. The resulting support and control sets are saved in global
> + * variables cxl_osc_support_set and cxl_osc_control_set. The internal
> + * functions cxl_osc_declare_support(), and cxl_osc_request_control() can be
> + * used to update the support and control sets in accordance with the ACPI
> + * rules for _OSC evaluation - most importantly, capabilities already granted
> + * should not be rescinded by either the OS or firmware.
> + */
> +
> +static u32 cxl_osc_support_set;
> +static u32 cxl_osc_control_set;
> +static DEFINE_MUTEX(acpi_desc_lock);
> +
> +struct pci_osc_bit_struct {
> + u32 bit;
> + char *desc;
> +};
> +
> +static struct pci_osc_bit_struct cxl_osc_support_bit[] = {
> + { CXL_OSC_PORT_REG_ACCESS_SUPPORT, "CXLPortRegAccess" },
> + { CXL_OSC_PORT_DEV_REG_ACCESS_SUPPORT, "CXLPortDevRegAccess" },
> + { CXL_OSC_PER_SUPPORT, "CXLProtocolErrorReporting" },
> + { CXL_OSC_NATIVE_HP_SUPPORT, "CXLNativeHotPlug" },
> +};
> +
> +static struct pci_osc_bit_struct cxl_osc_control_bit[] = {
> + { CXL_OSC_MEM_ERROR_CONTROL, "CXLMemErrorReporting" },
> +};
> +
> +static u8 cxl_osc_uuid_str[] = "68F2D50B-C469-4d8A-BD3D-941A103FD3FC";
> +
> +static void decode_osc_bits(struct device *dev, char *msg, u32 word,
> + struct pci_osc_bit_struct *table, int size)
> +{
> + char buf[80];
> + int i, len = 0;
> + struct pci_osc_bit_struct *entry;
> +
> + buf[0] = '\0';
> + for (i = 0, entry = table; i < size; i++, entry++)
> + if (word & entry->bit)
> + len += scnprintf(buf + len, sizeof(buf) - len, "%s%s",
> + len ? " " : "", entry->desc);
> +
> + dev_info(dev, "_OSC: %s [%s]\n", msg, buf);
> +}
> +
> +static void decode_cxl_osc_support(struct device *dev, char *msg, u32 word)
> +{
> + decode_osc_bits(dev, msg, word, cxl_osc_support_bit,
> + ARRAY_SIZE(cxl_osc_support_bit));
> +}
> +
> +static void decode_cxl_osc_control(struct device *dev, char *msg, u32 word)
> +{
> + decode_osc_bits(dev, msg, word, cxl_osc_control_bit,
> + ARRAY_SIZE(cxl_osc_control_bit));
> +}
> +
> +static acpi_status acpi_cap_run_osc(acpi_handle handle, const u32 *capbuf,
> + u8 *uuid_str, u32 *retval)
A nit: This is only called twice, every time with the same UUID, so it
would be good to avoid passing the UUID to this function.
> +{
> + struct acpi_osc_context context = {
> + .uuid_str = uuid_str,
> + .rev = 1,
> + .cap.length = 20,
> + .cap.pointer = (void *)capbuf,
> + };
> + acpi_status status;
> +
> + status = acpi_run_osc(handle, &context);
> + if (ACPI_SUCCESS(status)) {
> + /* pointer + offset to DWORD 5 */
> + *retval = *((u32 *)(context.ret.pointer + 16));
> + kfree(context.ret.pointer);
> + }
> + return status;
> +}
> +
The rest of the patch looks OK to me.
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