| Message ID | 20210130002438.1872527-2-ben.widawsky@intel.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | CXL 2.0 Support | expand |
On Fri, 29 Jan 2021, Ben Widawsky wrote: > diff --git a/drivers/cxl/Kconfig b/drivers/cxl/Kconfig > new file mode 100644 > index 000000000000..3b66b46af8a0 > --- /dev/null > +++ b/drivers/cxl/Kconfig > @@ -0,0 +1,35 @@ > +# SPDX-License-Identifier: GPL-2.0-only > +menuconfig CXL_BUS > + tristate "CXL (Compute Express Link) Devices Support" > + depends on PCI > + help > + CXL is a bus that is electrically compatible with PCI Express, 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 Express. > + Say 'y' to enable support for the configuration and management of > + devices supporting these protocols. > + > +if CXL_BUS > + > +config CXL_MEM > + tristate "CXL.mem: Endpoint Support" Nit: "CXL.mem: Memory Devices" or "CXL Memory Devices: CXL.mem" might look better, but feel free to ignore. Acked-by: David Rientjes <rientjes@google.com>
On Fri, 29 Jan 2021 16:24:25 -0800 Ben Widawsky <ben.widawsky@intel.com> wrote: > From: Dan Williams <dan.j.williams@intel.com> > > The CXL.mem protocol allows a device to act as a provider of "System > RAM" and/or "Persistent Memory" that is fully coherent as if the memory > was attached to the typical CPU memory controller. > > With the CXL-2.0 specification a PCI endpoint can implement a "Type-3" > device interface and give the operating system control over "Host > Managed Device Memory". See section 2.3 Type 3 CXL Device. > > The memory range exported by the device may optionally be described by > the platform firmware memory map, or by infrastructure like LIBNVDIMM to > provision persistent memory capacity from one, or more, CXL.mem devices. > > A pre-requisite for Linux-managed memory-capacity provisioning is this > cxl_mem driver that can speak the mailbox protocol defined in section > 8.2.8.4 Mailbox Registers. > > For now just land the initial driver boiler-plate and Documentation/ > infrastructure. > > Link: https://www.computeexpresslink.org/download-the-specification > Cc: Jonathan Corbet <corbet@lwn.net> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com> Hi Ben, One thing below about using defs from generic PCI headers where they are not CXL specific. > diff --git a/drivers/cxl/pci.h b/drivers/cxl/pci.h > new file mode 100644 > index 000000000000..a8a9935fa90b > --- /dev/null > +++ b/drivers/cxl/pci.h > @@ -0,0 +1,20 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ > +#ifndef __CXL_PCI_H__ > +#define __CXL_PCI_H__ > + > +#define PCI_CLASS_MEMORY_CXL 0x050210 > + > +/* > + * See section 8.1 Configuration Space Registers in the CXL 2.0 > + * Specification > + */ > +#define PCI_EXT_CAP_ID_DVSEC 0x23 > +#define PCI_DVSEC_VENDOR_ID_CXL 0x1E98 > +#define PCI_DVSEC_VENDOR_ID_OFFSET 0x4 > +#define PCI_DVSEC_ID_CXL 0x0 > +#define PCI_DVSEC_ID_OFFSET 0x8 include/uapi/linux/pci-regs.h includes equivalents of generic parts of this already though PCI_DVSEC_HEADER1 isn't exactly informative naming. > + > +#define PCI_DVSEC_ID_CXL_REGLOC 0x8 > + > +#endif /* __CXL_PCI_H__ */
> +cxl_mem-y := mem.o > diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c > new file mode 100644 > index 000000000000..f4ee9a507ac9 > --- /dev/null > +++ b/drivers/cxl/mem.c > @@ -0,0 +1,61 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ Can those two comments have the same type? As in either stay with // or do /*. Also the year is incorrect.
On Mon, Feb 01, 2021 at 12:34:11PM -0500, Konrad Rzeszutek Wilk wrote: > > +// SPDX-License-Identifier: GPL-2.0-only > > +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ > > Can those two comments have the same type? As in either > stay with // or do /*. No. // is only intended for the SPDX comments specifically so that they stand out.
> +static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec) > +{ > + int pos; > + > + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DVSEC); > + if (!pos) > + return 0; > + > + while (pos) { > + u16 vendor, id; > + > + pci_read_config_word(pdev, pos + PCI_DVSEC_VENDOR_ID_OFFSET, > + &vendor); > + pci_read_config_word(pdev, pos + PCI_DVSEC_ID_OFFSET, &id); > + if (vendor == PCI_DVSEC_VENDOR_ID_CXL && dvsec == id) > + return pos; > + > + pos = pci_find_next_ext_capability(pdev, pos, > + PCI_EXT_CAP_ID_DVSEC); > + } > + > + return 0; > +} There should be a patch with a generic version of this find a vendor specific capability helper on linux-pci. > +#define PCI_CLASS_MEMORY_CXL 0x050210 I think this should go into linux/pci_ids.h.
diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst new file mode 100644 index 000000000000..036e49553542 --- /dev/null +++ b/Documentation/driver-api/cxl/index.rst @@ -0,0 +1,12 @@ +.. SPDX-License-Identifier: GPL-2.0 + +==================== +Compute Express Link +==================== + +.. toctree:: + :maxdepth: 1 + + memory-devices + +.. only:: subproject and html diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst new file mode 100644 index 000000000000..43177e700d62 --- /dev/null +++ b/Documentation/driver-api/cxl/memory-devices.rst @@ -0,0 +1,29 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +=================================== +Compute Express Link Memory Devices +=================================== + +A Compute Express Link Memory Device is a CXL component that implements the +CXL.mem protocol. It contains some amount of volatile memory, persistent memory, +or both. It is enumerated as a PCI device for configuration and passing +messages over an MMIO mailbox. Its contribution to the System Physical +Address space is handled via HDM (Host Managed Device Memory) decoders +that optionally define a device's contribution to an interleaved address +range across multiple devices underneath a host-bridge or interleaved +across host-bridges. + +Driver Infrastructure +===================== + +This section covers the driver infrastructure for a CXL memory device. + +CXL Memory Device +----------------- + +.. kernel-doc:: drivers/cxl/mem.c + :doc: cxl mem + +.. kernel-doc:: drivers/cxl/mem.c + :internal: diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst index 2456d0a97ed8..d246a18fd78f 100644 --- a/Documentation/driver-api/index.rst +++ b/Documentation/driver-api/index.rst @@ -35,6 +35,7 @@ available subsections can be seen below. usb/index firewire pci/index + cxl/index spi i2c ipmb 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 fd11b9ac4cc3..678ea810410f 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..3b66b46af8a0 --- /dev/null +++ b/drivers/cxl/Kconfig @@ -0,0 +1,35 @@ +# SPDX-License-Identifier: GPL-2.0-only +menuconfig CXL_BUS + tristate "CXL (Compute Express Link) Devices Support" + depends on PCI + help + CXL is a bus that is electrically compatible with PCI Express, 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 Express. + Say 'y' to enable support for the configuration and management of + devices supporting these protocols. + +if CXL_BUS + +config CXL_MEM + tristate "CXL.mem: Endpoint Support" + help + The CXL.mem protocol allows a device to act as a provider of + "System RAM" and/or "Persistent Memory" that is fully coherent + as if the memory was attached to the typical CPU memory + controller. + + Say 'y/m' to enable a driver (named "cxl_mem.ko" when built as + a module) that will attach to CXL.mem devices for + configuration, provisioning, and health monitoring. This + driver is required for dynamic provisioning of CXL.mem + attached memory which is a prerequisite for persistent memory + support. Typically volatile memory is mapped by platform + firmware and included in the platform memory map, but in some + cases the OS is responsible for mapping that memory. See + Chapter 2.3 Type 3 CXL Device in the CXL 2.0 specification. + + If unsure say 'm'. +endif diff --git a/drivers/cxl/Makefile b/drivers/cxl/Makefile new file mode 100644 index 000000000000..4a30f7c3fc4a --- /dev/null +++ b/drivers/cxl/Makefile @@ -0,0 +1,4 @@ +# SPDX-License-Identifier: GPL-2.0 +obj-$(CONFIG_CXL_MEM) += cxl_mem.o + +cxl_mem-y := mem.o diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c new file mode 100644 index 000000000000..f4ee9a507ac9 --- /dev/null +++ b/drivers/cxl/mem.c @@ -0,0 +1,61 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ +#include <linux/module.h> +#include <linux/pci.h> +#include <linux/io.h> +#include "pci.h" + +static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec) +{ + int pos; + + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DVSEC); + if (!pos) + return 0; + + while (pos) { + u16 vendor, id; + + pci_read_config_word(pdev, pos + PCI_DVSEC_VENDOR_ID_OFFSET, + &vendor); + pci_read_config_word(pdev, pos + PCI_DVSEC_ID_OFFSET, &id); + if (vendor == PCI_DVSEC_VENDOR_ID_CXL && dvsec == id) + return pos; + + pos = pci_find_next_ext_capability(pdev, pos, + PCI_EXT_CAP_ID_DVSEC); + } + + return 0; +} + +static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id) +{ + struct device *dev = &pdev->dev; + int regloc; + + regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC); + if (!regloc) { + dev_err(dev, "register location dvsec not found\n"); + return -ENXIO; + } + + return 0; +} + +static const struct pci_device_id cxl_mem_pci_tbl[] = { + /* PCI class code for CXL.mem Type-3 Devices */ + { PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, PCI_ANY_ID, + PCI_CLASS_MEMORY_CXL, 0xffffff, 0 }, + { /* terminate list */ }, +}; +MODULE_DEVICE_TABLE(pci, cxl_mem_pci_tbl); + +static struct pci_driver cxl_mem_driver = { + .name = KBUILD_MODNAME, + .id_table = cxl_mem_pci_tbl, + .probe = cxl_mem_probe, +}; + +MODULE_LICENSE("GPL v2"); +module_pci_driver(cxl_mem_driver); diff --git a/drivers/cxl/pci.h b/drivers/cxl/pci.h new file mode 100644 index 000000000000..a8a9935fa90b --- /dev/null +++ b/drivers/cxl/pci.h @@ -0,0 +1,20 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* Copyright(c) 2020 Intel Corporation. All rights reserved. */ +#ifndef __CXL_PCI_H__ +#define __CXL_PCI_H__ + +#define PCI_CLASS_MEMORY_CXL 0x050210 + +/* + * See section 8.1 Configuration Space Registers in the CXL 2.0 + * Specification + */ +#define PCI_EXT_CAP_ID_DVSEC 0x23 +#define PCI_DVSEC_VENDOR_ID_CXL 0x1E98 +#define PCI_DVSEC_VENDOR_ID_OFFSET 0x4 +#define PCI_DVSEC_ID_CXL 0x0 +#define PCI_DVSEC_ID_OFFSET 0x8 + +#define PCI_DVSEC_ID_CXL_REGLOC 0x8 + +#endif /* __CXL_PCI_H__ */