[PATCH v3] drm/xe: Add device CXL capabilities identification

[Farah Kassabri]

As future Intel GPUs will use CXL interface with the host
servers, this patch will add check if the xe device has CXL
capabilities or not, by reading the PCIe standard DVSEC register
and identify the CXL vendor id.

Signed-off-by: Farah Kassabri <fkassabri at habana.ai>
---
Changes in v3:
fixes following review.

 drivers/gpu/drm/xe/Makefile          |  1 +
 drivers/gpu/drm/xe/xe_cxl.c          | 51 ++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_cxl.h          | 13 +++++++
 drivers/gpu/drm/xe/xe_device.c       |  5 +++
 drivers/gpu/drm/xe/xe_device_types.h | 10 ++++++
 5 files changed, 80 insertions(+)
 create mode 100644 drivers/gpu/drm/xe/xe_cxl.c
 create mode 100644 drivers/gpu/drm/xe/xe_cxl.h

diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index a5959bb7b1fb..65c0a0317ee7 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -65,6 +65,7 @@ $(uses_generated_oob): $(generated_oob)
 xe-y += xe_bb.o \
 	xe_bo.o \
 	xe_bo_evict.o \
+	xe_cxl.o \
 	xe_debugfs.o \
 	xe_devcoredump.o \
 	xe_device.o \
diff --git a/drivers/gpu/drm/xe/xe_cxl.c b/drivers/gpu/drm/xe/xe_cxl.c
new file mode 100644
index 000000000000..78e4179e965a
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_cxl.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#include "xe_cxl.h"
+#include "xe_device.h"
+#include "../drivers/cxl/cxlpci.h"
+
+enum {
+	CXL_DEV_TYPE_ONE = 1,
+	CXL_DEV_TYPE_TWO,
+	CXL_DEV_TYPE_THREE
+};
+
+/**
+ * xe_cxl_init_capabilities - set CXL device capabilities
+ * @xe: xe device structure
+ *
+ * Set CXL capabilities and information of the xe device.
+ *
+ * Return: 0 on success, negative value on failure.
+ */
+int xe_cxl_init_capabilities(struct xe_device *xe)
+{
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
+	u16 ctrl, cxl_dvsec;
+	int rc;
+
+	cxl_dvsec = pci_find_dvsec_capability(pdev, PCI_DVSEC_VENDOR_ID_CXL, CXL_DVSEC_PCIE_DEVICE);
+	if (!cxl_dvsec)
+		return -1;
+
+	rc = pci_read_config_word(pdev, cxl_dvsec + CXL_DVSEC_CTRL_OFFSET, &ctrl);
+	if (rc < 0) {
+		drm_err(&xe->drm, "Failed to read DVSEC_CTRL register(%d)\n", rc);
+		return rc;
+	}
+
+	xe->info.has_cxl_cap = true;
+	xe->cxl.dvsec = cxl_dvsec;
+
+	if (ctrl & CXL_DVSEC_MEM_ENABLE)
+		xe->cxl.type = (ctrl & BIT(0)) ? CXL_DEV_TYPE_TWO : CXL_DEV_TYPE_THREE;
+	else
+		xe->cxl.type = CXL_DEV_TYPE_ONE;
+
+	drm_dbg(&xe->drm, "The device has CXL capability, type %u\n", xe->cxl.type);
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/xe/xe_cxl.h b/drivers/gpu/drm/xe/xe_cxl.h
new file mode 100644
index 000000000000..82e36285c383
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_cxl.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2024 Intel Corporation
+ */
+
+#ifndef _XE_CXL_H_
+#define _XE_CXL_H_
+
+struct xe_device;
+
+int xe_cxl_init_capabilities(struct xe_device *xe);
+
+#endif
diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 5acf2c92789f..04677c9ff10f 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -50,6 +50,7 @@
 #include "xe_ttm_sys_mgr.h"
 #include "xe_vm.h"
 #include "xe_wait_user_fence.h"
+#include "xe_cxl.h"
 
 static int xe_file_open(struct drm_device *dev, struct drm_file *file)
 {
@@ -312,6 +313,10 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 	if (WARN_ON(err))
 		goto err;
 
+	err = xe_cxl_init_capabilities(xe);
+	if (err)
+		goto err;
+
 	return xe;
 
 err:
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index 8e7048ff3ee5..323c3d57fdb8 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -285,6 +285,8 @@ struct xe_device {
 		u8 has_atomic_enable_pte_bit:1;
 		/** @info.has_device_atomics_on_smem: Supports device atomics on SMEM */
 		u8 has_device_atomics_on_smem:1;
+		/** @info.has_cxl_cap: device has CXL capabilities */
+		u8 has_cxl_cap:1;
 
 #if IS_ENABLED(CONFIG_DRM_XE_DISPLAY)
 		struct {
@@ -321,6 +323,14 @@ struct xe_device {
 		struct ttm_resource_manager sys_mgr;
 	} mem;
 
+	/** @cxl: CXL info for device */
+	struct {
+		/** @cxl.dvsec: offset to device DVSEC */
+		u16 dvsec;
+		/** @cxl.type: CXL device type */
+		u16 type;
+	} cxl;
+
 	/** @sriov: device level virtualization data */
 	struct {
 		/** @sriov.__mode: SR-IOV mode (Don't access directly!) */
-- 
2.34.1