cxl/mem: Find device capabilities

Provide enough functionality to utilize the mailbox of a memory device.
The mailbox is used to interact with the firmware running on the memory
device. The flow is proven with one implemented command, "identify".
Because the class code has already told the driver this is a memory
device and the identify command is mandatory.

CXL devices contain an array of capabilities that describe the
interactions software can have with the device or firmware running on
the device. A CXL compliant device must implement the device status and
the mailbox capability. Additionally, a CXL compliant memory device must
implement the memory device capability. Each of the capabilities can
[will] provide an offset within the MMIO region for interacting with the
CXL device.

The capabilities tell the driver how to find and map the register space
for CXL Memory Devices. The registers are required to utilize the CXL
spec defined mailbox interface. The spec outlines two mailboxes, primary
and secondary. The secondary mailbox is earmarked for system firmware,
and not handled in this driver.

Primary mailboxes are capable of generating an interrupt when submitting
a background command. That implementation is saved for a later time.

Reported-by: Colin Ian King <colin.king@canonical.com> (coverity)
Reported-by: Dan Carpenter <dan.carpenter@oracle.com> (smatch)
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2)
Link: https://www.computeexpresslink.org/download-the-specification
Link: https://lore.kernel.org/r/20210217040958.1354670-3-ben.widawsky@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

Documentation/driver-api/cxl/memory-devices.rst

@@ -13,3 +13,17 @@ 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:

drivers/cxl/cxl.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright(c) 2020 Intel Corporation. */
+
+#ifndef __CXL_H__
+#define __CXL_H__
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+
+/* CXL 2.0 8.2.8.1 Device Capabilities Array Register */
+#define CXLDEV_CAP_ARRAY_OFFSET 0x0
+#define   CXLDEV_CAP_ARRAY_CAP_ID 0
+#define   CXLDEV_CAP_ARRAY_ID_MASK GENMASK_ULL(15, 0)
+#define   CXLDEV_CAP_ARRAY_COUNT_MASK GENMASK_ULL(47, 32)
+/* CXL 2.0 8.2.8.2 CXL Device Capability Header Register */
+#define CXLDEV_CAP_HDR_CAP_ID_MASK GENMASK(15, 0)
+/* CXL 2.0 8.2.8.2.1 CXL Device Capabilities */
+#define CXLDEV_CAP_CAP_ID_DEVICE_STATUS 0x1
+#define CXLDEV_CAP_CAP_ID_PRIMARY_MAILBOX 0x2
+#define CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX 0x3
+#define CXLDEV_CAP_CAP_ID_MEMDEV 0x4000
+
+/* CXL 2.0 8.2.8.4 Mailbox Registers */
+#define CXLDEV_MBOX_CAPS_OFFSET 0x00
+#define   CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK GENMASK(4, 0)
+#define CXLDEV_MBOX_CTRL_OFFSET 0x04
+#define   CXLDEV_MBOX_CTRL_DOORBELL BIT(0)
+#define CXLDEV_MBOX_CMD_OFFSET 0x08
+#define   CXLDEV_MBOX_CMD_COMMAND_OPCODE_MASK GENMASK_ULL(15, 0)
+#define   CXLDEV_MBOX_CMD_PAYLOAD_LENGTH_MASK GENMASK_ULL(36, 16)
+#define CXLDEV_MBOX_STATUS_OFFSET 0x10
+#define   CXLDEV_MBOX_STATUS_RET_CODE_MASK GENMASK_ULL(47, 32)
+#define CXLDEV_MBOX_BG_CMD_STATUS_OFFSET 0x18
+#define CXLDEV_MBOX_PAYLOAD_OFFSET 0x20
+
+/* CXL 2.0 8.2.8.5.1.1 Memory Device Status Register */
+#define CXLMDEV_STATUS_OFFSET 0x0
+#define   CXLMDEV_DEV_FATAL BIT(0)
+#define   CXLMDEV_FW_HALT BIT(1)
+#define   CXLMDEV_STATUS_MEDIA_STATUS_MASK GENMASK(3, 2)
+#define     CXLMDEV_MS_NOT_READY 0
+#define     CXLMDEV_MS_READY 1
+#define     CXLMDEV_MS_ERROR 2
+#define     CXLMDEV_MS_DISABLED 3
+#define CXLMDEV_READY(status)                                                  \
+	(FIELD_GET(CXLMDEV_STATUS_MEDIA_STATUS_MASK, status) ==                \
+	 CXLMDEV_MS_READY)
+#define   CXLMDEV_MBOX_IF_READY BIT(4)
+#define   CXLMDEV_RESET_NEEDED_MASK GENMASK(7, 5)
+#define     CXLMDEV_RESET_NEEDED_NOT 0
+#define     CXLMDEV_RESET_NEEDED_COLD 1
+#define     CXLMDEV_RESET_NEEDED_WARM 2
+#define     CXLMDEV_RESET_NEEDED_HOT 3
+#define     CXLMDEV_RESET_NEEDED_CXL 4
+#define CXLMDEV_RESET_NEEDED(status)                                           \
+	(FIELD_GET(CXLMDEV_RESET_NEEDED_MASK, status) !=                       \
+	 CXLMDEV_RESET_NEEDED_NOT)
+
+/**
+ * struct cxl_mem - A CXL memory device
+ * @pdev: The PCI device associated with this CXL device.
+ * @regs: IO mappings to the device's MMIO
+ * @status_regs: CXL 2.0 8.2.8.3 Device Status Registers
+ * @mbox_regs: CXL 2.0 8.2.8.4 Mailbox Registers
+ * @memdev_regs: CXL 2.0 8.2.8.5 Memory Device Registers
+ * @payload_size: Size of space for payload
+ *                (CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register)
+ * @mbox_mutex: Mutex to synchronize mailbox access.
+ * @firmware_version: Firmware version for the memory device.
+ * @pmem_range: Persistent memory capacity information.
+ * @ram_range: Volatile memory capacity information.
+ */
+struct cxl_mem {
+	struct pci_dev *pdev;
+	void __iomem *regs;
+
+	void __iomem *status_regs;
+	void __iomem *mbox_regs;
+	void __iomem *memdev_regs;
+
+	size_t payload_size;
+	struct mutex mbox_mutex; /* Protects device mailbox and firmware */
+	char firmware_version[0x10];
+
+	struct range pmem_range;
+	struct range ram_range;
+};
+
+#endif /* __CXL_H__ */

drivers/cxl/pci.h

@@ -9,9 +9,23 @@
  * See section 8.1 Configuration Space Registers in the CXL 2.0
  * Specification
  */
+#define PCI_DVSEC_HEADER1_LENGTH_MASK	GENMASK(31, 20)
 #define PCI_DVSEC_VENDOR_ID_CXL		0x1E98
 #define PCI_DVSEC_ID_CXL		0x0
 
 #define PCI_DVSEC_ID_CXL_REGLOC_OFFSET		0x8
+#define PCI_DVSEC_ID_CXL_REGLOC_BLOCK1_OFFSET	0xC
+
+/* BAR Indicator Register (BIR) */
+#define CXL_REGLOC_BIR_MASK GENMASK(2, 0)
+
+/* Register Block Identifier (RBI) */
+#define CXL_REGLOC_RBI_MASK GENMASK(15, 8)
+#define CXL_REGLOC_RBI_EMPTY 0
+#define CXL_REGLOC_RBI_COMPONENT 1
+#define CXL_REGLOC_RBI_VIRT 2
+#define CXL_REGLOC_RBI_MEMDEV 3
+
+#define CXL_REGLOC_ADDR_MASK GENMASK(31, 16)
 
 #endif /* __CXL_PCI_H__ */