[PATCH 03/14] cxl/mem: Find device capabilities

Ben Widawsky
2021-01-30T10:24:09Z

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. 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.

For more details see 8.2.8 of the CXL 2.0 specification (see Link).

Link: https://www.computeexpresslink.org/download-the-specification
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
drivers/cxl/cxl.h | 78 ++++++++++++++++++++++++++++++++++-
drivers/cxl/mem.c | 102 +++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 178 insertions(+), 2 deletions(-)

diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index d81d0ba4617c..a3da7f8050c4 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -4,6 +4,37 @@
#ifndef __CXL_H__
#define __CXL_H__

+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/io.h>
+
+#define CXL_SET_FIELD(value, field) \
+ ({ \
+ WARN_ON(!FIELD_FIT(field##_MASK, value)); \
+ FIELD_PREP(field##_MASK, value); \
+ })
+
+#define CXL_GET_FIELD(word, field) FIELD_GET(field##_MASK, word)
+
+/* Device Capabilities (CXL 2.0 - 8.2.8.1) */
+#define CXLDEV_CAP_ARRAY_OFFSET 0x0
+#define CXLDEV_CAP_ARRAY_CAP_ID 0
+#define CXLDEV_CAP_ARRAY_ID_MASK GENMASK(15, 0)
+#define CXLDEV_CAP_ARRAY_COUNT_MASK GENMASK(47, 32)
+/* (CXL 2.0 - 8.2.8.2.1) */
+#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 Device Mailbox (CXL 2.0 - 8.2.8.4) */
+#define CXLDEV_MB_CAPS_OFFSET 0x00
+#define CXLDEV_MB_CAP_PAYLOAD_SIZE_MASK GENMASK(4, 0)
+#define CXLDEV_MB_CTRL_OFFSET 0x04
+#define CXLDEV_MB_CMD_OFFSET 0x08
+#define CXLDEV_MB_STATUS_OFFSET 0x10
+#define CXLDEV_MB_BG_CMD_STATUS_OFFSET 0x18
+
/**
* struct cxl_mem - A CXL memory device
* @pdev: The PCI device associated with this CXL device.
@@ -12,6 +43,51 @@
struct cxl_mem {
struct pci_dev *pdev;
void __iomem *regs;
+
+ /* Cap 0001h - CXL_CAP_CAP_ID_DEVICE_STATUS */
+ struct {
+ void __iomem *regs;
+ } status;
+
+ /* Cap 0002h - CXL_CAP_CAP_ID_PRIMARY_MAILBOX */
+ struct {
+ void __iomem *regs;
+ size_t payload_size;
+ } mbox;
+
+ /* Cap 4000h - CXL_CAP_CAP_ID_MEMDEV */
+ struct {
+ void __iomem *regs;
+ } mem;
};

-#endif
+#define cxl_reg(type) \
+ static inline void cxl_write_##type##_reg32(struct cxl_mem *cxlm, \
+ u32 reg, u32 value) \
+ { \
+ void __iomem *reg_addr = 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 = 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 = 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 = cxlm->type.regs; \
+ return readq(reg_addr + reg); \
+ }
+
+cxl_reg(status);
+cxl_reg(mbox);
+
+#endif /* __CXL_H__ */
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index a869c8dc24cc..fa14d51243ee 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -6,6 +6,99 @@
#include "pci.h"
#include "cxl.h"

+/**
+ * cxl_mem_setup_regs() - Setup necessary MMIO.
+ * @cxlm: The CXL memory device to communicate with.
+ *
+ * Return: 0 if all necessary registers mapped.
+ *
+ * A memory device is required by spec to implement a certain set of MMIO
+ * regions. The purpose of this function is to enumerate and map those
+ * registers.
+ *
+ * XXX: Register accessors need the mappings set up by this function, so
+ * any reads or writes must be read(b|w|l|q) or write(b|w|l|q)
+ */
+static int cxl_mem_setup_regs(struct cxl_mem *cxlm)
+{
+ struct device *dev = &cxlm->pdev->dev;
+ int cap, cap_count;
+ u64 cap_array;
+
+ cap_array = readq(cxlm->regs + CXLDEV_CAP_ARRAY_OFFSET);
+ if (CXL_GET_FIELD(cap_array, CXLDEV_CAP_ARRAY_ID) != CXLDEV_CAP_ARRAY_CAP_ID)
+ return -ENODEV;
+
+ cap_count = CXL_GET_FIELD(cap_array, CXLDEV_CAP_ARRAY_COUNT);
+
+ for (cap = 1; cap <= cap_count; cap++) {
+ void __iomem *register_block;
+ u32 offset;
+ u16 cap_id;
+
+ cap_id = readl(cxlm->regs + cap * 0x10) & 0xffff;
+ offset = readl(cxlm->regs + cap * 0x10 + 0x4);
+ register_block = cxlm->regs + offset;
+
+ switch (cap_id) {
+ case CXLDEV_CAP_CAP_ID_DEVICE_STATUS:
+ dev_dbg(dev, "found Status capability (0x%x)\n",
+ offset);
+ cxlm->status.regs = register_block;
+ break;
+ case CXLDEV_CAP_CAP_ID_PRIMARY_MAILBOX:
+ dev_dbg(dev, "found Mailbox capability (0x%x)\n",
+ offset);
+ cxlm->mbox.regs = register_block;
+ break;
+ case CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX:
+ dev_dbg(dev,
+ "found Secondary Mailbox capability (0x%x)\n",
+ offset);
+ break;
+ case CXLDEV_CAP_CAP_ID_MEMDEV:
+ dev_dbg(dev, "found Memory Device capability (0x%x)\n",
+ offset);
+ cxlm->mem.regs = register_block;
+ break;
+ default:
+ dev_warn(dev, "Unknown cap ID: %d (0x%x)\n", cap_id,
+ offset);
+ break;
+ }
+ }
+
+ if (!cxlm->status.regs || !cxlm->mbox.regs || !cxlm->mem.regs) {
+ dev_err(dev, "registers not found: %s%s%s\n",
+ !cxlm->status.regs ? "status " : "",
+ !cxlm->mbox.regs ? "mbox " : "",
+ !cxlm->mem.regs ? "mem" : "");
+ return -ENXIO;
+ }
+
+ return 0;
+}
+
+static int cxl_mem_setup_mailbox(struct cxl_mem *cxlm)
+{
+ const int cap = cxl_read_mbox_reg32(cxlm, CXLDEV_MB_CAPS_OFFSET);
+
+ cxlm->mbox.payload_size =
+ 1 << CXL_GET_FIELD(cap, CXLDEV_MB_CAP_PAYLOAD_SIZE);
+
+ /* 8.2.8.4.3 */
+ if (cxlm->mbox.payload_size < 256) {
+ dev_err(&cxlm->pdev->dev, "Mailbox is too small (%zub)",
+ cxlm->mbox.payload_size);
+ return -ENXIO;
+ }
+
+ dev_dbg(&cxlm->pdev->dev, "Mailbox payload sized %zu",
+ cxlm->mbox.payload_size);
+
+ return 0;
+}
+
/**
* cxl_mem_create() - Create a new &struct cxl_mem.
* @pdev: The pci device associated with the new &struct cxl_mem.
@@ -119,7 +212,14 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
}
}

- return rc;
+ if (rc)
+ return rc;
+
+ rc = cxl_mem_setup_regs(cxlm);
+ if (rc)
+ return rc;
+
+ return cxl_mem_setup_mailbox(cxlm);
}

static const struct pci_device_id cxl_mem_pci_tbl[] = {
--
2.30.0