[RFC PATCH 5/9] cxl/mem: Find device capabilities

Ben Widawsky
2020-11-11T05:45:00Z

CXL devices contain an array of capabilities that describe the
interactions software can interact with the device, or firmware running
on the device. A CXL compliant device must implement the device status
and the mailbox capability. 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.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
drivers/cxl/cxl.h | 89 +++++++++++++++++++++++++++++++++++++++++++++++
drivers/cxl/mem.c | 58 +++++++++++++++++++++++++++---
2 files changed, 143 insertions(+), 4 deletions(-)
create mode 100644 drivers/cxl/cxl.h

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
new file mode 100644
index 000000000000..02858ae63d6d
--- /dev/null
+++ b/drivers/cxl/cxl.h
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright(c) 2020 Intel Corporation. All rights reserved.
+
+#ifndef __CXL_H__
+#define __CXL_H__
+
+/* Device */
+#define CXLDEV_CAP_ARRAY_REG 0x0
+#define CXLDEV_CAP_ARRAY_CAP_ID 0
+#define CXLDEV_CAP_ARRAY_ID(x) ((x) & 0xffff)
+#define CXLDEV_CAP_ARRAY_COUNT(x) (((x) >> 32) & 0xffff)
+
+#define CXL_CAPABILITIES_CAP_ID_DEVICE_STATUS 1
+#define CXL_CAPABILITIES_CAP_ID_PRIMARY_MAILBOX 2
+#define CXL_CAPABILITIES_CAP_ID_SECONDARY_MAILBOX 3
+#define CXL_CAPABILITIES_CAP_ID_MEMDEV 0x4000
+
+/* Mailbox */
+#define CXLDEV_MB_CAPS 0x00
+#define CXLDEV_MB_CAP_PAYLOAD_SIZE(cap) ((cap) & 0x1F)
+#define CXLDEV_MB_CTRL 0x04
+#define CXLDEV_MB_CMD 0x08
+#define CXLDEV_MB_STATUS 0x10
+#define CXLDEV_MB_BG_CMD_STATUS 0x18
+
+struct cxl_mem {
+ struct pci_dev *pdev;
+ void __iomem *regs;
+
+ /* Cap 0000h */
+ struct {
+ void __iomem *regs;
+ } status;
+
+ /* Cap 0002h */
+ struct {
+ void __iomem *regs;
+ size_t payload_size;
+ } mbox;
+
+ /* Cap 0040h */
+ struct {
+ void __iomem *regs;
+ } mem;
+};
+
+#define cxl_reg(type) \
+ static inline void cxl_write_##type##_reg32(struct cxl_mem *cxlm, \
+ u32 reg, u32 value) \
+ { \
+ void __iomem *reg_addr = READ_ONCE(cxlm->type.regs); \
+ writel(value, reg_addr + reg); \
+ } \
+ static inline void cxl_write_##type##_reg64(struct cxl_mem *cxlm, \
+ u32 reg, u64 value) \
+ { \
+ void __iomem *reg_addr = READ_ONCE(cxlm->type.regs); \
+ writeq(value, reg_addr + reg); \
+ } \
+ static inline u32 cxl_read_##type##_reg32(struct cxl_mem *cxlm, \
+ u32 reg) \
+ { \
+ void __iomem *reg_addr = READ_ONCE(cxlm->type.regs); \
+ return readl(reg_addr + reg); \
+ } \
+ static inline u64 cxl_read_##type##_reg64(struct cxl_mem *cxlm, \
+ u32 reg) \
+ { \
+ void __iomem *reg_addr = READ_ONCE(cxlm->type.regs); \
+ return readq(reg_addr + reg); \
+ }
+
+cxl_reg(status)
+cxl_reg(mbox)
+
+static inline u32 __cxl_raw_read_reg32(struct cxl_mem *cxlm, u32 reg)
+{
+ void __iomem *reg_addr = READ_ONCE(cxlm->regs);
+
+ return readl(reg_addr + reg);
+}
+
+static inline u64 __cxl_raw_read_reg64(struct cxl_mem *cxlm, u32 reg)
+{
+ void __iomem *reg_addr = READ_ONCE(cxlm->regs);
+
+ return readq(reg_addr + reg);
+}
+#endif /* __CXL_H__ */
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index 8d9b9ab6c5ea..4109ef7c3ecb 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -5,11 +5,57 @@
#include <linux/io.h>
#include "acpi.h"
#include "pci.h"
+#include "cxl.h"

-struct cxl_mem {
- struct pci_dev *pdev;
- void __iomem *regs;
-};
+static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
+{
+ u64 cap_array;
+ int cap;
+
+ cap_array = __cxl_raw_read_reg64(cxlm, CXLDEV_CAP_ARRAY_REG);
+ if (CXLDEV_CAP_ARRAY_ID(cap_array) != CXLDEV_CAP_ARRAY_CAP_ID)
+ return -ENODEV;
+
+ for (cap = 1; cap <= CXLDEV_CAP_ARRAY_COUNT(cap_array); cap++) {
+ void *__iomem register_block;
+ u32 offset;
+ u16 cap_id;
+
+ cap_id = __cxl_raw_read_reg32(cxlm, cap * 0x10) & 0xffff;
+ offset = __cxl_raw_read_reg32(cxlm, cap * 0x10 + 0x4);
+ register_block = cxlm->regs + offset;
+
+ switch (cap_id) {
+ case CXL_CAPABILITIES_CAP_ID_DEVICE_STATUS:
+ dev_dbg(&cxlm->pdev->dev, "found Status capability\n");
+ cxlm->status.regs = register_block;
+ break;
+ case CXL_CAPABILITIES_CAP_ID_PRIMARY_MAILBOX:
+ dev_dbg(&cxlm->pdev->dev,
+ "found Mailbox capability\n");
+ cxlm->mbox.regs = register_block;
+ cxlm->mbox.payload_size = CXLDEV_MB_CAP_PAYLOAD_SIZE(cap_id);
+ break;
+ case CXL_CAPABILITIES_CAP_ID_SECONDARY_MAILBOX:
+ dev_dbg(&cxlm->pdev->dev,
+ "found UNSUPPORTED Secondary Mailbox capability\n");
+ break;
+ case CXL_CAPABILITIES_CAP_ID_MEMDEV:
+ dev_dbg(&cxlm->pdev->dev,
+ "found Memory Device capability\n");
+ cxlm->mem.regs = register_block;
+ break;
+ default:
+ dev_err(&cxlm->pdev->dev, "Unknown cap ID: %d\n", cap_id);
+ return -ENXIO;
+ }
+ }
+
+ if (!cxlm->status.regs || !cxlm->mbox.regs || !cxlm->mem.regs)
+ return -ENXIO;
+
+ return 0;
+}

static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev, u32 reg_lo, u32 reg_hi)
{
@@ -110,6 +156,10 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
if (IS_ERR(cxlm))
return -ENXIO;

+ rc = cxl_mem_setup_regs(cxlm);
+ if (rc)
+ return rc;
+
pci_set_drvdata(pdev, cxlm);

return 0;
--
2.29.2