[PATCH] fpga: add DFL driver for CXL Cache IP block

[Matthew Gerlach]

From: Tim Whisonant <tim.whisonant@xxxxxxxxx>

Add a Device Feature List (DFL) driver for the
Intel CXL Cache IP block. The driver
provides a means of accessing the device MMIO and the
capability to pin buffers and program their physical
addresses into the HE-Cache registers. User interface
is exposed via /dev/dfl-cxl-cache.X as described in
include/uapi/linux/fpga-dfl.h.

Signed-off-by: Tim Whisonant <tim.whisonant@xxxxxxxxx>
Co-developed-by: Ananda Ravuri <ananda.ravuri@xxxxxxxxx>
Signed-off-by: Ananda Ravuri <ananda.ravuri@xxxxxxxxx>
Signed-off-by: Matthew Gerlach <matthew.gerlach@xxxxxxxxxxxxxxx>
---
 drivers/fpga/Kconfig          |  11 +
 drivers/fpga/Makefile         |   1 +
 drivers/fpga/dfl-cxl-cache.c  | 645 ++++++++++++++++++++++++++++++++++
 include/uapi/linux/fpga-dfl.h |  98 ++++++
 4 files changed, 755 insertions(+)
 create mode 100644 drivers/fpga/dfl-cxl-cache.c

diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
index 2f689ac4ba3a..00931a3deebf 100644
--- a/drivers/fpga/Kconfig
+++ b/drivers/fpga/Kconfig
@@ -257,6 +257,17 @@ config FPGA_M10_BMC_SEC_UPDATE
 	  (BMC) and provides support for secure updates for the BMC image,
 	  the FPGA image, the Root Entry Hashes, etc.
 
+config FPGA_DFL_CXL_CACHE
+	tristate "Intel CXL cache driver"
+	depends on DRM && FPGA_DFL
+	help
+	  This is the driver for CXL cache Accelerated Function Unit
+	  (AFU) which configures the IP and provides DMA buffer management
+	  to user space.
+
+	  To compile this driver as a module, chose M here: the
+	  module will be called dfl_cxl_cache.
+
 config FPGA_MGR_MICROCHIP_SPI
 	tristate "Microchip Polarfire SPI FPGA manager"
 	depends on SPI
diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
index 352a2612623e..970902810845 100644
--- a/drivers/fpga/Makefile
+++ b/drivers/fpga/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_FPGA_DFL_NIOS_INTEL_PAC_N3000)	+= dfl-n3000-nios.o
 
 # Drivers for FPGAs which implement DFL
 obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o
+obj-$(CONFIG_FPGA_DFL_CXL_CACHE)	+= dfl-cxl-cache.o
 
 # KUnit tests
 obj-$(CONFIG_FPGA_KUNIT_TESTS)		+= tests/
diff --git a/drivers/fpga/dfl-cxl-cache.c b/drivers/fpga/dfl-cxl-cache.c
new file mode 100644
index 000000000000..ee2ae04ac058
--- /dev/null
+++ b/drivers/fpga/dfl-cxl-cache.c
@@ -0,0 +1,645 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * DFL device driver for Host Exerciser Cache private feature.
+ *
+ * Provides a means of accessing the device MMIO and the
+ * capability to pin buffers and program their physical
+ * addresses into the HE-Cache registers. User interface
+ * is exposed via /dev/dfl-cxl-cache.X as described in
+ * include/uapi/linux/fpga-dfl.h.
+ *
+ * Copyright (C) 2023 Intel Corporation, Inc.
+ *
+ * Authors:
+ *   Tim Whisonant <tim.whisonant@xxxxxxxxx>
+ *   Ananda Ravuri <ananda.ravuri@xxxxxxxxx>
+ */
+
+#include <linux/bitfield.h>
+#include <linux/cdev.h>
+#include <linux/cleanup.h>
+#include <linux/container_of.h>
+#include <linux/dfl.h>
+#include <linux/errno.h>
+#include <linux/fpga-dfl.h>
+#include <linux/highmem.h>
+#include <linux/io.h>
+#include <linux/mmap_lock.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pgtable.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include <drm/drm_cache.h>
+
+#define DFL_CXL_CACHE_DRIVER_NAME	"dfl-cxl-cache"
+#define FME_FEATURE_ID_CXL_CACHE	0x25
+
+struct dfl_cxl_cache_buffer_region {
+	struct rb_node node;
+	u32 flags;
+	u64 user_addr;
+	u64 length;
+	struct page **pages;
+	phys_addr_t phys;
+	u64 offset[DFL_ARRAY_MAX_SIZE];
+};
+
+struct dfl_cxl_cache {
+	struct cdev cdev;
+	struct dfl_device *ddev;
+	int id;
+	struct device *dev;
+	atomic_t opened;
+	void __iomem *mmio_base;
+	int mmio_size;
+	struct dfl_cxl_cache_region_info rinfo;
+	struct rb_root dma_regions;
+};
+
+static DEFINE_MUTEX(dfl_cxl_cache_class_lock);
+static struct class *dfl_cxl_cache_class;
+static dev_t dfl_cxl_cache_devt;
+static int dfl_cxl_cache_devices;
+
+static int dfl_cxl_cache_open(struct inode *inode, struct file *filp)
+{
+	struct dfl_cxl_cache *cxl_cache = container_of(inode->i_cdev, struct dfl_cxl_cache, cdev);
+
+	if (atomic_cmpxchg(&cxl_cache->opened, 0, 1))
+		return -EBUSY;
+
+	filp->private_data = cxl_cache;
+
+	return 0;
+}
+
+static long cxl_cache_ioctl_check_extension(struct dfl_cxl_cache *cxl_cache, unsigned long arg)
+{
+	/* No extension support for now */
+	return 0;
+}
+
+static long cxl_cache_ioctl_get_region_info(struct dfl_cxl_cache *cxl_cache, void __user *arg)
+{
+	struct dfl_cxl_cache_region_info rinfo;
+	unsigned long minsz;
+
+	minsz = offsetofend(struct dfl_cxl_cache_region_info, offset);
+	if (copy_from_user(&rinfo, arg, minsz))
+		return -EFAULT;
+
+	if (rinfo.argsz < minsz)
+		return -EINVAL;
+
+	rinfo.flags = cxl_cache->rinfo.flags;
+	rinfo.size = cxl_cache->rinfo.size;
+	rinfo.offset = cxl_cache->rinfo.offset;
+
+	if (copy_to_user(arg, &rinfo, sizeof(rinfo)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static void cxl_cache_unpin_pages(struct device *dev, struct page ***pages, unsigned long length)
+{
+	const long npages = PFN_DOWN(length);
+
+	if (!*pages)
+		return;
+
+	unpin_user_pages(*pages, npages);
+	kfree(*pages);
+	*pages = NULL;
+	account_locked_vm(current->mm, npages, false);
+}
+
+static bool cxl_cache_check_continuous_pages(struct page **pages, unsigned long length)
+{
+	int i;
+	const int npages = PFN_DOWN(length);
+
+	for (i = 0; i < npages - 1; i++)
+		if (page_to_pfn(pages[i]) + 1 != page_to_pfn(pages[i + 1]))
+			return false;
+
+	return true;
+}
+
+static int cxl_cache_dma_pin_pages(struct dfl_cxl_cache *cxl_cache,
+				   struct dfl_cxl_cache_buffer_region *region)
+{
+	int ret, pinned;
+	unsigned int flags = FOLL_LONGTERM;
+	const int npages = PFN_DOWN(region->length);
+
+	ret = account_locked_vm(current->mm, npages, true);
+	if (ret) {
+		dev_err(cxl_cache->dev, "account_locked_vm() failed: %d\n", ret);
+		return ret;
+	}
+
+	region->pages = kcalloc(npages, sizeof(struct page *), GFP_KERNEL);
+	if (!region->pages) {
+		ret = -ENOMEM;
+		goto unlock_vm;
+	}
+
+	if (region->flags & DFL_CXL_BUFFER_MAP_WRITABLE)
+		flags |= FOLL_WRITE;
+
+	pinned = pin_user_pages_fast(region->user_addr, npages, flags, region->pages);
+	if (pinned == npages)
+		return 0;
+
+	ret = -EFAULT;
+	if (pinned > 0)
+		unpin_user_pages(region->pages, pinned);
+
+	kfree(region->pages);
+unlock_vm:
+	account_locked_vm(current->mm, npages, false);
+	return ret;
+}
+
+static void cxl_cache_dma_region_remove(struct dfl_cxl_cache *cxl_cache,
+					struct dfl_cxl_cache_buffer_region *region)
+{
+	rb_erase(&region->node, &cxl_cache->dma_regions);
+}
+
+static bool dma_region_check_user_addr(struct dfl_cxl_cache_buffer_region *region, u64 user_addr,
+				       u64 size)
+{
+	if (!size && region->user_addr != user_addr)
+		return false;
+
+	return (region->user_addr <= user_addr) &&
+		(region->length + region->user_addr >= user_addr + size);
+}
+
+static struct dfl_cxl_cache_buffer_region*
+cxl_cache_dma_region_find(struct dfl_cxl_cache *cxl_cache, u64 user_addr, u64 size)
+{
+	struct rb_node *node = cxl_cache->dma_regions.rb_node;
+
+	while (node) {
+		struct dfl_cxl_cache_buffer_region *region;
+
+		region = container_of(node, struct dfl_cxl_cache_buffer_region, node);
+
+		if (dma_region_check_user_addr(region, user_addr, size))
+			return region;
+
+		if (user_addr < region->user_addr)
+			node = node->rb_left;
+		else if (user_addr > region->user_addr)
+			node = node->rb_right;
+		else
+			break;
+	}
+
+	return NULL;
+}
+
+static int cxl_cache_dma_region_add(struct dfl_cxl_cache *cxl_cache,
+				    struct dfl_cxl_cache_buffer_region *region)
+{
+	struct rb_node **new, *parent = NULL;
+
+	new = &cxl_cache->dma_regions.rb_node;
+
+	while (*new) {
+		struct dfl_cxl_cache_buffer_region *this;
+
+		this = container_of(*new, struct dfl_cxl_cache_buffer_region, node);
+		parent = *new;
+
+		if (dma_region_check_user_addr(this, region->user_addr, region->length))
+			return -EEXIST;
+
+		if (region->user_addr < this->user_addr)
+			new = &((*new)->rb_left);
+		else if (region->user_addr > this->user_addr)
+			new = &((*new)->rb_right);
+		else
+			return -EEXIST;
+	}
+
+	rb_link_node(&region->node, parent, new);
+	rb_insert_color(&region->node, &cxl_cache->dma_regions);
+
+	return 0;
+}
+
+static void fixup_ptes(struct mm_struct *mm, unsigned long start, unsigned long end)
+{
+	unsigned long addr;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *pte;
+
+	for (addr = start; addr < end; addr += PAGE_SIZE) {
+		pgd = pgd_offset(mm, addr);
+		if (pgd_bad(*pgd) || pgd_none(*pgd))
+			continue;
+
+		p4d = p4d_offset(pgd, addr);
+		if (p4d_bad(*p4d) || p4d_none(*p4d))
+			continue;
+
+		pud = pud_offset(p4d, addr);
+		if (pud_bad(*pud) || pud_none(*pud))
+			continue;
+
+		pmd = pmd_offset(pud, addr);
+		if (pmd_bad(*pmd) || pmd_none(*pmd))
+			continue;
+
+		pte = pte_offset_kernel(pmd, addr);
+		if (!pte_none(*pte) && pte_present(*pte))
+			*pte = pte_wrprotect(*pte);
+	}
+}
+
+static long cxl_cache_set_region_read_only(struct dfl_cxl_cache *cxl_cache,
+					   struct dfl_cxl_cache_buffer_region *region)
+{
+	struct vm_area_struct *vma;
+	long ret = 0;
+
+	vma = vma_lookup(current->mm, region->user_addr);
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
+		dev_err(cxl_cache->dev, "vma_lookup() failed: %ld\n", ret);
+		return ret;
+	}
+
+	mmap_write_lock(current->mm);
+
+	/* Mark the pages as non-cached and write-protected. */
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vm_flags_clear(vma, VM_WRITE);
+
+	fixup_ptes(current->mm, vma->vm_start, vma->vm_end);
+
+	mmap_write_unlock(current->mm);
+
+	/* Flush all remaining cache entries. */
+	drm_clflush_virt_range(page_address(region->pages[0]), region->length);
+
+	return ret;
+}
+
+static long cxl_cache_ioctl_numa_buffer_map(struct dfl_cxl_cache *cxl_cache, void __user *arg)
+{
+	int i = 0;
+	unsigned long minsz = 0;
+	long ret = 0;
+	struct dfl_cxl_cache_buffer_map dma_map;
+	struct dfl_cxl_cache_buffer_region *region;
+
+	minsz = offsetofend(struct dfl_cxl_cache_buffer_map, csr_array);
+	if (copy_from_user(&dma_map, arg, minsz)) {
+		dev_err(cxl_cache->dev, "fails to copy from user space buffer\n");
+		return -EFAULT;
+	}
+	if (dma_map.argsz < minsz) {
+		dev_err(cxl_cache->dev, "invalid ioctl buffer size\n");
+		return -EINVAL;
+	}
+
+	/* Check Inputs, only accept page-aligned user memory region with valid length */
+	if (!PAGE_ALIGNED(dma_map.user_addr) || !PAGE_ALIGNED(dma_map.length) ||
+	    !(dma_map.length)) {
+		dev_err(cxl_cache->dev, "length is not page-aligned or the length is zero\n");
+		return -EINVAL;
+	}
+
+	/* Check overflow */
+	if (dma_map.user_addr + dma_map.length < dma_map.user_addr) {
+		dev_err(cxl_cache->dev, "dma buffer check overflow\n");
+		return -EINVAL;
+	}
+
+	region = kzalloc(sizeof(*region), GFP_KERNEL);
+	if (!region)
+		return -ENOMEM;
+
+	region->flags = dma_map.flags;
+	region->user_addr = dma_map.user_addr;
+	region->length = dma_map.length;
+
+	/* Pin the user memory region */
+	ret = cxl_cache_dma_pin_pages(cxl_cache, region);
+	if (ret) {
+		dev_err(cxl_cache->dev, "failed to pin pages\n");
+		goto free_region;
+	}
+
+	/* Only accept continuous pages, return error else */
+	if (!cxl_cache_check_continuous_pages(region->pages, region->length)) {
+		dev_err(cxl_cache->dev, "pages are not continuous\n");
+		ret = -EINVAL;
+		goto out_unpin_pages;
+	}
+
+	if (!(region->flags & DFL_CXL_BUFFER_MAP_WRITABLE)) {
+		ret = cxl_cache_set_region_read_only(cxl_cache, region);
+		if (ret)
+			goto out_unpin_pages;
+	}
+
+	ret = cxl_cache_dma_region_add(cxl_cache, region);
+	if (ret) {
+		dev_err(cxl_cache->dev, "failed to add dma region\n");
+		goto out_unpin_pages;
+	}
+
+	region->phys = page_to_phys(region->pages[0]);
+
+	for (i = 0; i < DFL_ARRAY_MAX_SIZE; i++) {
+		if (dma_map.csr_array[i] && dma_map.csr_array[i] < cxl_cache->rinfo.size)
+			writeq(region->phys, cxl_cache->mmio_base + dma_map.csr_array[i]);
+	}
+
+	return 0;
+
+out_unpin_pages:
+	cxl_cache_unpin_pages(cxl_cache->dev, &region->pages, region->length);
+free_region:
+	kfree(region);
+	return ret;
+}
+
+static long cxl_cache_ioctl_numa_buffer_unmap(struct dfl_cxl_cache *cxl_cache, void __user *arg)
+{
+	unsigned long minsz = 0;
+	long ret = 0;
+	int i = 0;
+	struct dfl_cxl_cache_buffer_unmap dma_unmap;
+	struct dfl_cxl_cache_buffer_region *region;
+
+	minsz = offsetofend(struct dfl_cxl_cache_buffer_unmap, csr_array);
+	if (copy_from_user(&dma_unmap, arg, minsz)) {
+		dev_err(cxl_cache->dev, "fails to copy from user space buffer\n");
+		return -EFAULT;
+	}
+	if (dma_unmap.argsz < minsz) {
+		dev_err(cxl_cache->dev, "invalid ioctl buffer size\n");
+		return -EINVAL;
+	}
+
+	region = cxl_cache_dma_region_find(cxl_cache, dma_unmap.user_addr, dma_unmap.length);
+	if (!region) {
+		dev_err(cxl_cache->dev, "fails to find buffer\n");
+		return -EINVAL;
+	}
+
+	cxl_cache_dma_region_remove(cxl_cache, region);
+	cxl_cache_unpin_pages(cxl_cache->dev, &region->pages, region->length);
+
+	for (i = 0; i < DFL_ARRAY_MAX_SIZE; i++) {
+		if (dma_unmap.csr_array[i] && dma_unmap.csr_array[i] < cxl_cache->rinfo.size)
+			writeq(0, cxl_cache->mmio_base + dma_unmap.csr_array[i]);
+	}
+
+	kfree(region);
+	return ret;
+}
+
+static long dfl_cxl_cache_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct dfl_cxl_cache *cxl_cache = filp->private_data;
+
+	switch (cmd) {
+	case DFL_FPGA_GET_API_VERSION:
+		return DFL_FPGA_GET_API_VERSION;
+	case DFL_FPGA_CHECK_EXTENSION:
+		return cxl_cache_ioctl_check_extension(cxl_cache, arg);
+	case DFL_CXL_CACHE_GET_REGION_INFO:
+		return cxl_cache_ioctl_get_region_info(cxl_cache, (void __user *)arg);
+	case DFL_CXL_CACHE_NUMA_BUFFER_MAP:
+		return cxl_cache_ioctl_numa_buffer_map(cxl_cache, (void __user *)arg);
+	case DFL_CXL_CACHE_NUMA_BUFFER_UNMAP:
+		return cxl_cache_ioctl_numa_buffer_unmap(cxl_cache, (void __user *)arg);
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct vm_operations_struct cxl_cache_vma_ops = {
+#ifdef CONFIG_HAVE_IOREMAP_PROT
+	.access = generic_access_phys,
+#endif
+};
+
+static int dfl_cxl_cache_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct dfl_cxl_cache *cxl_cache = filp->private_data;
+	u64 size = vma->vm_end - vma->vm_start;
+	u64 offset;
+
+	if (!(vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+
+	if (!(cxl_cache->rinfo.flags & DFL_CXL_CACHE_REGION_MMAP))
+		return -EINVAL;
+
+	if ((vma->vm_flags & VM_READ) && !(cxl_cache->rinfo.flags & DFL_CXL_CACHE_REGION_READ))
+		return -EPERM;
+
+	if ((vma->vm_flags & VM_WRITE) && !(cxl_cache->rinfo.flags & DFL_CXL_CACHE_REGION_WRITE))
+		return -EPERM;
+
+	offset = PFN_PHYS(vma->vm_pgoff);
+
+	/* Support debug access to the mapping */
+	vma->vm_ops = &cxl_cache_vma_ops;
+
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+	return remap_pfn_range(vma, vma->vm_start,
+			       PFN_DOWN(cxl_cache->ddev->mmio_res.start +
+			       (offset - cxl_cache->rinfo.offset)),
+			       size, vma->vm_page_prot);
+}
+
+static void cxl_cache_dma_region_destroy(struct dfl_cxl_cache *cxl_cache)
+{
+	struct rb_node *node = rb_first(&cxl_cache->dma_regions);
+	struct dfl_cxl_cache_buffer_region *region;
+
+	while (node) {
+		region = container_of(node, struct dfl_cxl_cache_buffer_region, node);
+
+		rb_erase(node, &cxl_cache->dma_regions);
+
+		if (region->pages)
+			cxl_cache_unpin_pages(cxl_cache->dev, &region->pages, region->length);
+
+		node = rb_next(node);
+		kfree(region);
+	}
+}
+
+static int dfl_cxl_cache_release(struct inode *inode, struct file *filp)
+{
+	struct dfl_cxl_cache *cxl_cache = filp->private_data;
+
+	cxl_cache_dma_region_destroy(cxl_cache);
+	atomic_set(&cxl_cache->opened, 0);
+	return 0;
+}
+
+static const struct file_operations dfl_cxl_cache_fops = {
+	.owner = THIS_MODULE,
+	.open = dfl_cxl_cache_open,
+	.release = dfl_cxl_cache_release,
+	.unlocked_ioctl = dfl_cxl_cache_ioctl,
+	.mmap = dfl_cxl_cache_mmap,
+};
+
+static void cxl_cache_dev_release(struct device *dev)
+{
+	struct dfl_cxl_cache *cxl_cache = dev_get_drvdata(dev);
+
+	cdev_del(&cxl_cache->cdev);
+}
+
+static void cxl_cache_chardev_uinit(struct dfl_cxl_cache *cxl_cache)
+{
+	device_destroy(dfl_cxl_cache_class,
+		       MKDEV(MAJOR(dfl_cxl_cache_devt), cxl_cache->id));
+}
+
+static int cxl_cache_chardev_init(struct dfl_cxl_cache *cxl_cache,
+				  struct dfl_device *ddev,
+				  void __iomem *mmio_base)
+{
+	int ret;
+
+	dev_set_drvdata(&ddev->dev, cxl_cache);
+	cxl_cache->ddev = ddev;
+	cxl_cache->mmio_base = mmio_base;
+	cxl_cache->id = dfl_cxl_cache_devices++;
+	cxl_cache->dma_regions = RB_ROOT;
+
+	cxl_cache->rinfo.argsz = sizeof(struct dfl_cxl_cache_region_info);
+	cxl_cache->rinfo.flags = DFL_CXL_CACHE_REGION_READ | DFL_CXL_CACHE_REGION_WRITE |
+			   DFL_CXL_CACHE_REGION_MMAP;
+	cxl_cache->rinfo.size = resource_size(&ddev->mmio_res);
+	cxl_cache->rinfo.offset = 0;
+
+	cxl_cache->dev = device_create(dfl_cxl_cache_class, &ddev->dev,
+				       MKDEV(MAJOR(dfl_cxl_cache_devt), cxl_cache->id),
+				       cxl_cache, DFL_CXL_CACHE_DRIVER_NAME ".%d",
+				       cxl_cache->id);
+
+	if (IS_ERR(cxl_cache->dev)) {
+		ret = PTR_ERR(cxl_cache->dev);
+		dev_err(&ddev->dev, "device_create failed: %d\n", ret);
+		cxl_cache->dev = NULL;
+		return ret;
+	}
+	cxl_cache->dev->release = cxl_cache_dev_release;
+
+	cdev_init(&cxl_cache->cdev, &dfl_cxl_cache_fops);
+	cxl_cache->cdev.owner = THIS_MODULE;
+	cxl_cache->cdev.ops = &dfl_cxl_cache_fops;
+
+	ret = cdev_add(&cxl_cache->cdev, cxl_cache->dev->devt, 1);
+	if (ret)
+		dev_err(cxl_cache->dev, "cdev_add failed: %d\n", ret);
+
+	return ret;
+}
+
+static int dfl_cxl_cache_probe(struct dfl_device *ddev)
+{
+	int ret = 0;
+	void __iomem *mmio_base;
+	struct dfl_cxl_cache *cxl_cache;
+
+	guard(mutex)(&dfl_cxl_cache_class_lock);
+
+	if (!dfl_cxl_cache_class) {
+		dfl_cxl_cache_class = class_create(DFL_CXL_CACHE_DRIVER_NAME);
+		if (IS_ERR(dfl_cxl_cache_class)) {
+			ret = PTR_ERR(dfl_cxl_cache_class);
+			dfl_cxl_cache_class = NULL;
+			dev_err_probe(&ddev->dev, ret, "class_create failed\n");
+			return ret;
+		}
+	}
+
+	if (!MAJOR(dfl_cxl_cache_devt)) {
+		ret = alloc_chrdev_region(&dfl_cxl_cache_devt, 0,
+					  MINORMASK,
+					  DFL_CXL_CACHE_DRIVER_NAME);
+		if (ret) {
+			dev_err_probe(&ddev->dev, ret, "alloc_chrdev_region failed\n");
+			dfl_cxl_cache_devt = MKDEV(0, 0);
+			return ret;
+		}
+	}
+
+	mmio_base = devm_ioremap_resource(&ddev->dev, &ddev->mmio_res);
+	if (IS_ERR(mmio_base))
+		return PTR_ERR(mmio_base);
+
+	cxl_cache = devm_kzalloc(&ddev->dev, sizeof(*cxl_cache), GFP_KERNEL);
+	if (!cxl_cache)
+		return -ENOMEM;
+
+	ret = cxl_cache_chardev_init(cxl_cache, ddev, mmio_base);
+	if (ret)
+		dev_err_probe(&ddev->dev, ret, "cxl_cache_chardev_init failed\n");
+
+	return ret;
+}
+
+static void dfl_cxl_cache_remove(struct dfl_device *ddev)
+{
+	struct dfl_cxl_cache *cxl_cache = dev_get_drvdata(&ddev->dev);
+
+	guard(mutex)(&dfl_cxl_cache_class_lock);
+	cxl_cache_chardev_uinit(cxl_cache);
+
+	if (dfl_cxl_cache_devices-- == 0) {
+		if (dfl_cxl_cache_class) {
+			class_destroy(dfl_cxl_cache_class);
+			dfl_cxl_cache_class = NULL;
+		}
+
+		if (MAJOR(dfl_cxl_cache_devt)) {
+			unregister_chrdev_region(dfl_cxl_cache_devt, MINORMASK);
+			dfl_cxl_cache_devt = MKDEV(0, 0);
+		}
+	}
+}
+
+static const struct dfl_device_id dfl_cxl_cache_ids[] = {
+	{ FME_ID, FME_FEATURE_ID_CXL_CACHE },
+	{ }
+};
+MODULE_DEVICE_TABLE(dfl, dfl_cxl_cache_ids);
+
+static struct dfl_driver dfl_cxl_cache_driver = {
+	.drv	= {
+		.name	= DFL_CXL_CACHE_DRIVER_NAME,
+	},
+	.id_table = dfl_cxl_cache_ids,
+	.probe   = dfl_cxl_cache_probe,
+	.remove = dfl_cxl_cache_remove,
+};
+module_dfl_driver(dfl_cxl_cache_driver);
+
+MODULE_DESCRIPTION("DFL CXL Cache driver");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/fpga-dfl.h b/include/uapi/linux/fpga-dfl.h
index 1621b077bf21..866f50b99eb6 100644
--- a/include/uapi/linux/fpga-dfl.h
+++ b/include/uapi/linux/fpga-dfl.h
@@ -31,6 +31,7 @@
 #define DFL_FPGA_BASE 0
 #define DFL_PORT_BASE 0x40
 #define DFL_FME_BASE 0x80
+#define DFL_CXL_CACHE_BASE 0xA0
 
 /* Common IOCTLs for both FME and AFU file descriptor */
 
@@ -276,4 +277,101 @@ struct dfl_fpga_fme_port_pr {
 					     DFL_FME_BASE + 4,	\
 					     struct dfl_fpga_irq_set)
 
+ /**
+  * DFL_CXL_CACHE_GET_REGION_INFO - _IOWR(DFL_FPGA_MAGIC, DFL_CXL_CACHE_BASE + 0,
+  *                                      struct dfl_cxl_cache_region_info)
+  *
+  * Retrieve information about a device memory region.
+  * Caller provides struct dfl_cxl_cache_region_info with flags.
+  * Driver returns the region info in other fields.
+  * Return: 0 on success, -errno on failure.
+  */
+
+#define DFL_CXL_CACHE_GET_REGION_INFO _IO(DFL_FPGA_MAGIC, DFL_CXL_CACHE_BASE + 0)
+
+  /**
+   * struct dfl_cxl_cache_region_info - CXL cache region information
+   * @argsz: structure length
+   * @flags: access permission
+   * @size: region size (bytes)
+   * @offset: region offset from start of device fd
+   *
+   * to retrieve  information about a device memory region
+   */
+struct dfl_cxl_cache_region_info {
+	__u32 argsz;
+	__u32 flags;
+#define DFL_CXL_CACHE_REGION_READ	_BITUL(0)
+#define DFL_CXL_CACHE_REGION_WRITE	_BITUL(1)
+#define DFL_CXL_CACHE_REGION_MMAP	_BITUL(2)
+	__u64 size;
+	__u64 offset;
+};
+
+/**
+ * DFL_CXL_CACHE_NUMA_BUFFER_MAP - _IOWR(DFL_FPGA_MAGIC, DFL_CXL_CACHE_BASE + 1,
+ *                                      struct dfl_cxl_cache_buffer_map)
+ *
+ * Map the user memory per user_addr, length and numa node which are
+ * provided by caller. The driver allocates memory on the numa node,
+ * converts the user's virtual addressto a continuous physical address,
+ * and writes the physical address to the cxl cache read/write address table CSR.
+ *
+ * This interface only accepts page-size aligned user memory for mapping.
+ * Return: 0 on success, -errno on failure.
+ */
+
+#define DFL_ARRAY_MAX_SIZE   0x10
+
+#define DFL_CXL_CACHE_NUMA_BUFFER_MAP    _IO(DFL_FPGA_MAGIC,  DFL_CXL_CACHE_BASE + 1)
+
+/**
+ * struct dfl_cxl_cache_buffer_map - maps user address to physical address.
+ * @argsz: structure length
+ * @flags: flags
+ * @user_addr: user mmap virtual address
+ * @length: length of mapping (bytes)
+ * @csr_array: array of region address offset
+ *
+ * maps user allocated virtual address to physical address.
+ */
+struct dfl_cxl_cache_buffer_map {
+	__u32 argsz;
+#define DFL_CXL_BUFFER_MAP_WRITABLE	1
+	__u32 flags;
+	__u64 user_addr;
+	__u64 length;
+	__u64 csr_array[DFL_ARRAY_MAX_SIZE];
+};
+
+/**
+ * DFL_CXL_CACHE_NUMA_BUFFER_UNMAP - _IOWR(DFL_FPGA_MAGIC, DFL_CXL_CACHE_BASE + 1,
+ *                                      struct dfl_cxl_cache_buffer_unmap)
+ *
+ * Unmaps the user memory per user_addr and length which are provided by caller
+ * The driver deletes the physical pages of the user address and writes a zero
+ * to the read/write address table CSR.
+ * Return: 0 on success, -errno on failure.
+ */
+
+#define DFL_CXL_CACHE_NUMA_BUFFER_UNMAP  _IO(DFL_FPGA_MAGIC,  DFL_CXL_CACHE_BASE + 2)
+
+/**
+ * struct dfl_cxl_cache_buffer_unmap - unmaps user allocated memory.
+ * @argsz: structure length
+ * @flags: flags
+ * @user_addr: user mmap virtual address
+ * @length: length of mapping (bytes)
+ * @csr_array: array of region address offset
+ *
+ * unmaps user allocated memory.
+ */
+struct dfl_cxl_cache_buffer_unmap {
+	__u32 argsz;
+	__u32 flags;
+	__u64 user_addr;
+	__u64 length;
+	__u64 csr_array[DFL_ARRAY_MAX_SIZE];
+};
+
 #endif /* _UAPI_LINUX_FPGA_DFL_H */
-- 
2.34.1