[PATCH 02/14] cxl/mem: Map memory device registers

Ben Widawsky
2021-01-30T00:25:53Z

All the necessary bits are initialized in order to find and map the
register space for CXL Memory Devices. This is accomplished by using the
Register Locator DVSEC (CXL 2.0 - 8.1.9.1) to determine which PCI BAR to
use, and how much of an offset from that BAR should be added.

If the memory device registers are found and mapped a new internal data
structure tracking device state is allocated.

Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
---
drivers/cxl/cxl.h | 17 ++++++++++
drivers/cxl/mem.c | 83 +++++++++++++++++++++++++++++++++++++++++++++--
drivers/cxl/pci.h | 14 ++++++++
3 files changed, 112 insertions(+), 2 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..d81d0ba4617c
--- /dev/null
+++ b/drivers/cxl/cxl.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright(c) 2020 Intel Corporation. */
+
+#ifndef __CXL_H__
+#define __CXL_H__
+
+/**
+ * struct cxl_mem - A CXL memory device
+ * @pdev: The PCI device associated with this CXL device.
+ * @regs: IO mappings to the device's MMIO
+ */
+struct cxl_mem {
+ struct pci_dev *pdev;
+ void __iomem *regs;
+};
+
+#endif
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index f4ee9a507ac9..a869c8dc24cc 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -4,6 +4,58 @@
#include <linux/pci.h>
#include <linux/io.h>
#include "pci.h"
+#include "cxl.h"
+
+/**
+ * cxl_mem_create() - Create a new &struct cxl_mem.
+ * @pdev: The pci device associated with the new &struct cxl_mem.
+ * @reg_lo: Lower 32b of the register locator
+ * @reg_hi: Upper 32b of the register locator.
+ *
+ * Return: The new &struct cxl_mem on success, NULL on failure.
+ *
+ * Map the BAR for a CXL memory device. This BAR has the memory device's
+ * registers for the device as specified in CXL specification.
+ */
+static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev, u32 reg_lo,
+ u32 reg_hi)
+{
+ struct device *dev = &pdev->dev;
+ struct cxl_mem *cxlm;
+ void __iomem *regs;
+ u64 offset;
+ u8 bar;
+ int rc;
+
+ offset = ((u64)reg_hi << 32) | (reg_lo & CXL_REGLOC_ADDR_MASK);
+ bar = (reg_lo >> CXL_REGLOC_BIR_SHIFT) & CXL_REGLOC_BIR_MASK;
+
+ /* Basic sanity check that BAR is big enough */
+ if (pci_resource_len(pdev, bar) < offset) {
+ dev_err(dev, "BAR%d: %pr: too small (offset: %#llx)\n", bar,
+ &pdev->resource[bar], (unsigned long long)offset);
+ return NULL;
+ }
+
+ rc = pcim_iomap_regions(pdev, BIT(bar), pci_name(pdev));
+ if (rc != 0) {
+ dev_err(dev, "failed to map registers\n");
+ return NULL;
+ }
+
+ cxlm = devm_kzalloc(&pdev->dev, sizeof(*cxlm), GFP_KERNEL);
+ if (!cxlm) {
+ dev_err(dev, "No memory available\n");
+ return NULL;
+ }
+
+ regs = pcim_iomap_table(pdev)[bar];
+ cxlm->pdev = pdev;
+ cxlm->regs = regs + offset;
+
+ dev_dbg(dev, "Mapped CXL Memory Device resource\n");
+ return cxlm;
+}

static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
{
@@ -32,15 +84,42 @@ static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
{
struct device *dev = &pdev->dev;
- int regloc;
+ struct cxl_mem *cxlm;
+ int rc, regloc, i;
+
+ rc = pcim_enable_device(pdev);
+ if (rc)
+ return rc;

regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC);
if (!regloc) {
dev_err(dev, "register location dvsec not found\n");
return -ENXIO;
}
+ regloc += 0xc; /* Skip DVSEC + reserved fields */

- return 0;
+ rc = -ENXIO;
+ for (i = regloc; i < regloc + 0x24; i += 8) {
+ u32 reg_lo, reg_hi;
+ u8 reg_type;
+
+ /* "register low and high" contain other bits */
+ pci_read_config_dword(pdev, i, &reg_lo);
+ pci_read_config_dword(pdev, i + 4, &reg_hi);
+
+ reg_type =
+ (reg_lo >> CXL_REGLOC_RBI_SHIFT) & CXL_REGLOC_RBI_MASK;
+
+ if (reg_type == CXL_REGLOC_RBI_MEMDEV) {
+ rc = 0;
+ cxlm = cxl_mem_create(pdev, reg_lo, reg_hi);
+ if (!cxlm)
+ rc = -ENODEV;
+ break;
+ }
+ }
+
+ return rc;
}

static const struct pci_device_id cxl_mem_pci_tbl[] = {
diff --git a/drivers/cxl/pci.h b/drivers/cxl/pci.h
index a8a9935fa90b..df222edb6ac3 100644
--- a/drivers/cxl/pci.h
+++ b/drivers/cxl/pci.h
@@ -17,4 +17,18 @@

#define PCI_DVSEC_ID_CXL_REGLOC 0x8

+/* BAR Indicator Register (BIR) */
+#define CXL_REGLOC_BIR_SHIFT 0
+#define CXL_REGLOC_BIR_MASK 0x7
+
+/* Register Block Identifier (RBI) */
+#define CXL_REGLOC_RBI_SHIFT 8
+#define CXL_REGLOC_RBI_MASK 0xff
+#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 0xffff0000
+
#endif /* __CXL_PCI_H__ */
--
2.30.0