Re: [RFC PATCH 1/9] cxl/acpi: Add an acpi_cxl module for the CXL interconnect

Rafael J. Wysocki
2020-11-17T14:33:04Z

On Wed, Nov 11, 2020 at 6:45 AM Ben Widawsky <ben.widawsky@intel.com> wrote:
>
> From: Vishal Verma <vishal.l.verma@intel.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.
>
> Cc: Ben Widawsky <ben.widawsky@intel.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> ---
> drivers/Kconfig | 1 +
> drivers/Makefile | 1 +
> drivers/cxl/Kconfig | 30 +++++++++++
> drivers/cxl/Makefile | 5 ++
> drivers/cxl/acpi.c | 119 ++++++++++++++++++++++++++++++++++++++++++
> drivers/cxl/acpi.h | 15 ++++++
> include/acpi/actbl1.h | 52 ++++++++++++++++++
> 7 files changed, 223 insertions(+)
> create mode 100644 drivers/cxl/Kconfig
> create mode 100644 drivers/cxl/Makefile
> create mode 100644 drivers/cxl/acpi.c
> create mode 100644 drivers/cxl/acpi.h
>
> diff --git a/drivers/Kconfig b/drivers/Kconfig
> index dcecc9f6e33f..62c753a73651 100644
> --- a/drivers/Kconfig
> +++ b/drivers/Kconfig
> @@ -6,6 +6,7 @@ menu "Device Drivers"
> source "drivers/amba/Kconfig"
> source "drivers/eisa/Kconfig"
> source "drivers/pci/Kconfig"
> +source "drivers/cxl/Kconfig"
> source "drivers/pcmcia/Kconfig"
> source "drivers/rapidio/Kconfig"
>
> diff --git a/drivers/Makefile b/drivers/Makefile
> index c0cd1b9075e3..5dad349de73b 100644
> --- a/drivers/Makefile
> +++ b/drivers/Makefile
> @@ -73,6 +73,7 @@ obj-$(CONFIG_NVM) += lightnvm/
> obj-y += base/ block/ misc/ mfd/ nfc/
> obj-$(CONFIG_LIBNVDIMM) += nvdimm/
> obj-$(CONFIG_DAX) += dax/
> +obj-$(CONFIG_CXL_BUS) += cxl/
> obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf/
> obj-$(CONFIG_NUBUS) += nubus/
> obj-y += macintosh/
> diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig
> new file mode 100644
> index 000000000000..dd724bd364df
> --- /dev/null
> +++ b/drivers/cxl/Kconfig
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +menuconfig CXL_BUS
> + tristate "CXL (Compute Express Link) Devices Support"
> + help
> + CXL is a bus that is electrically compatible with PCI-E, but layers
> + three protocols on that signalling (CXL.io, CXL.cache, and CXL.mem). The
> + CXL.cache protocol allows devices to hold cachelines locally, the
> + CXL.mem protocol allows devices to be fully coherent memory targets, the
> + CXL.io protocol is equivalent to PCI-E. Say 'y' to enable support for
> + the configuration and management of devices supporting these protocols.
> +
> +if CXL_BUS
> +
> +config CXL_BUS_PROVIDER
> + tristate
> +
> +config CXL_ACPI
> + tristate "CXL Platform Support"
> + depends on ACPI
> + default CXL_BUS
> + select CXL_BUS_PROVIDER
> + help
> + CXL Platform Support is a prerequisite for any CXL device driver that
> + wants to claim ownership of the component register space. By default
> + platform firmware assumes Linux is unaware of CXL capabilities and
> + requires explicit opt-in. This platform component also mediates
> + resources described by the CEDT (CXL Early Discovery Table)
> +
> + Say 'y' to enable CXL (Compute Express Link) drivers.
> +endif
> diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile
> new file mode 100644
> index 000000000000..d38cd34a2582
> --- /dev/null
> +++ b/drivers/cxl/Makefile
> @@ -0,0 +1,5 @@
> +# SPDX-License-Identifier: GPL-2.0
> +obj-$(CONFIG_CXL_ACPI) += cxl_acpi.o
> +
> +ccflags-y += -DDEFAULT_SYMBOL_NAMESPACE=CXL
> +cxl_acpi-y := acpi.o
> diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
> new file mode 100644
> index 000000000000..26e4f73838a7
> --- /dev/null
> +++ b/drivers/cxl/acpi.c
> @@ -0,0 +1,119 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright(c) 2020 Intel Corporation. All rights reserved.
> + */
> +#include <linux/list_sort.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/sysfs.h>
> +#include <linux/list.h>
> +#include <linux/acpi.h>
> +#include <linux/sort.h>
> +#include <linux/pci.h>
> +#include "acpi.h"
> +
> +static void acpi_cxl_desc_init(struct acpi_cxl_desc *acpi_desc, struct device *dev)
> +{
> + dev_set_drvdata(dev, acpi_desc);
> + acpi_desc->dev = dev;
> +}
> +
> +static void acpi_cedt_put_table(void *table)
> +{
> + acpi_put_table(table);
> +}
> +
> +static int acpi_cxl_add(struct acpi_device *adev)
> +{
> + struct acpi_cxl_desc *acpi_desc;
> + struct device *dev = &adev->dev;
> + struct acpi_table_header *tbl;
> + acpi_status status = AE_OK;
> + acpi_size sz;
> + int rc = 0;
> +
> + status = acpi_get_table(ACPI_SIG_CEDT, 0, &tbl);
> + if (ACPI_FAILURE(status)) {
> + dev_err(dev, "failed to find CEDT at startup\n");
> + return 0;
> + }
> +
> + rc = devm_add_action_or_reset(dev, acpi_cedt_put_table, tbl);
> + if (rc)
> + return rc;
> + sz = tbl->length;
> + dev_info(dev, "found CEDT at startup: %lld bytes\n", sz);
> +
> + acpi_desc = devm_kzalloc(dev, sizeof(*acpi_desc), GFP_KERNEL);
> + if (!acpi_desc)
> + return -ENOMEM;
> + acpi_cxl_desc_init(acpi_desc, &adev->dev);
> +
> + acpi_desc->acpi_header = *tbl;
> +
> + return 0;
> +}
> +
> +static int acpi_cxl_remove(struct acpi_device *adev)
> +{
> + return 0;
> +}
> +
> +static const struct acpi_device_id acpi_cxl_ids[] = {
> + { "ACPI0017", 0 },
> + { "", 0 },
> +};
> +MODULE_DEVICE_TABLE(acpi, acpi_cxl_ids);
> +
> +static struct acpi_driver acpi_cxl_driver = {

First of all, no new acpi_driver instances, pretty please!

acpi_default_enumeration() should create a platform device with the
ACPI0017 ID for you. Can't you provide a driver for this one?

> + .name = KBUILD_MODNAME,
> + .ids = acpi_cxl_ids,
> + .ops = {
> + .add = acpi_cxl_add,
> + .remove = acpi_cxl_remove,
> + },
> +};
> +
> +/*
> + * If/when CXL support is defined by other platform firmware the kernel
> + * will need a mechanism to select between the platform specific version
> + * of this routine, until then, hard-code ACPI assumptions
> + */
> +int cxl_bus_prepared(struct pci_dev *pdev)
> +{
> + struct acpi_device *adev;
> + struct pci_dev *root_port;
> + struct device *root;
> +
> + root_port = pcie_find_root_port(pdev);
> + if (!root_port)
> + return -ENXIO;
> +
> + root = root_port->dev.parent;
> + if (!root)
> + return -ENXIO;
> +
> + adev = ACPI_COMPANION(root);
> + if (!adev)
> + return -ENXIO;
> +
> + /* TODO: OSC enabling */
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(cxl_bus_prepared);
> +
> +static __init int acpi_cxl_init(void)
> +{
> + return acpi_bus_register_driver(&acpi_cxl_driver);
> +}
> +
> +static __exit void acpi_cxl_exit(void)
> +{
> + acpi_bus_unregister_driver(&acpi_cxl_driver);
> +}
> +
> +module_init(acpi_cxl_init);
> +module_exit(acpi_cxl_exit);
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Intel Corporation");
> diff --git a/drivers/cxl/acpi.h b/drivers/cxl/acpi.h
> new file mode 100644
> index 000000000000..011505475cc6
> --- /dev/null
> +++ b/drivers/cxl/acpi.h
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +// Copyright(c) 2020 Intel Corporation. All rights reserved.
> +
> +#ifndef __CXL_ACPI_H__
> +#define __CXL_ACPI_H__
> +#include <linux/acpi.h>
> +
> +struct acpi_cxl_desc {
> + struct acpi_table_header acpi_header;
> + struct device *dev;
> +};
> +
> +int cxl_bus_prepared(struct pci_dev *pci_dev);
> +
> +#endif /* __CXL_ACPI_H__ */
> diff --git a/include/acpi/actbl1.h b/include/acpi/actbl1.h
> index 43549547ed3e..70f745f526e3 100644
> --- a/include/acpi/actbl1.h
> +++ b/include/acpi/actbl1.h
> @@ -28,6 +28,7 @@
> #define ACPI_SIG_BERT "BERT" /* Boot Error Record Table */
> #define ACPI_SIG_BGRT "BGRT" /* Boot Graphics Resource Table */
> #define ACPI_SIG_BOOT "BOOT" /* Simple Boot Flag Table */
> +#define ACPI_SIG_CEDT "CEDT" /* CXL Early Discovery Table */
> #define ACPI_SIG_CPEP "CPEP" /* Corrected Platform Error Polling table */
> #define ACPI_SIG_CSRT "CSRT" /* Core System Resource Table */
> #define ACPI_SIG_DBG2 "DBG2" /* Debug Port table type 2 */
> @@ -1624,6 +1625,57 @@ struct acpi_ibft_target {
> u16 reverse_chap_secret_offset;
> };
>
> +/*******************************************************************************
> + *
> + * CEDT - CXL Early Discovery Table (ACPI 6.4)
> + * Version 1
> + *
> + ******************************************************************************/
> +
> +struct acpi_table_cedt {
> + struct acpi_table_header header; /* Common ACPI table header */
> + u32 reserved;
> +};
> +
> +/* Values for CEDT structure types */
> +
> +enum acpi_cedt_type {
> + ACPI_CEDT_TYPE_HOST_BRIDGE = 0, /* CHBS - CXL Host Bridge Structure */
> + ACPI_CEDT_TYPE_CFMWS = 1, /* CFMWS - CXL Fixed Memory Window Structure */
> +};
> +
> +struct acpi_cedt_structure {
> + u8 type;
> + u8 reserved;
> + u16 length;
> +};
> +
> +/*
> + * CEDT Structures, correspond to Type in struct acpi_cedt_structure
> + */
> +
> +/* 0: CXL Host Bridge Structure */
> +
> +struct acpi_cedt_chbs {
> + struct acpi_cedt_structure header;
> + u32 uid;
> + u32 version;
> + u32 reserved1;
> + u64 base;
> + u32 length;
> + u32 reserved2;
> +};
> +
> +/* Values for version field above */
> +
> +#define ACPI_CEDT_CHBS_VERSION_CXL11 (0)
> +#define ACPI_CEDT_CHBS_VERSION_CXL20 (1)
> +
> +/* Values for length field above */
> +
> +#define ACPI_CEDT_CHBS_LENGTH_CXL11 (0x2000)
> +#define ACPI_CEDT_CHBS_LENGTH_CXL20 (0x10000)
> +
> /* Reset to default packing */
>
> #pragma pack()
> --
> 2.29.2
>