[v3,04/30] drm/pagemap: Add DRM pagemap

Commit Message

Matthew Brost Dec. 17, 2024, 11:33 p.m. UTC

From: Thomas Hellström <[e-mail]>

Introduce drm_pagemap ops to map and unmap dma to VRAM resources. In the
local memory case it's a matter of merely providing an offset into the
device's physical address. For future p2p the map and unmap functions may
encode as needed.

Similar to how dma-buf works, let the memory provider (drm_pagemap) provide
the mapping functionality.

v3:
 - Move to drm level include

Signed-off-by: Matthew Brost <[e-mail]>
Signed-off-by: Thomas Hellström <[e-mail]>
---
 include/drm/drm_pagemap.h | 103 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 include/drm/drm_pagemap.h

Patch

diff --git a/include/drm/drm_pagemap.h b/include/drm/drm_pagemap.h
new file mode 100644
index 000000000000..b6b387b81479
--- /dev/null
+++ b/include/drm/drm_pagemap.h
@@ -0,0 +1,103 @@ 
+/* SPDX-License-Identifier: MIT */
+#ifndef _DRM_PAGEMAP_H_
+#define _DRM_PAGEMAP_H_
+
+#include <linux/dma-direction.h>
+#include <linux/hmm.h>
+#include <linux/types.h>
+
+struct drm_pagemap;
+struct device;
+
+/**
+ * enum drm_interconnect_protocol - Used to identify an interconnect protocol.
+ */
+enum drm_interconnect_protocol {
+	DRM_INTERCONNECT_SYSTEM,    /* DMA map is system pages. */
+	DRM_INTERCONNECT_PCIE_P2P,  /* DMA map is PCIE P2P */
+	DRM_INTERCONNECT_DRIVER,    /* DMA map is driver defined */
+	/* A driver can add private values beyond DRM_INTERCONNECT_DRIVER */
+};
+
+/**
+ * struct drm_pagemap_dma_addr - DMA address representation.
+ * @addr: The dma address or driver-defined address for driver private interconnects.
+ * @proto: The interconnect protocol.
+ * @order: The page order of the dma mapping. (Size is PAGE_SIZE << order).
+ * @dir: The DMA direction.
+ *
+ * Note: There is room for improvement here. We should be able to pack into
+ * 64 bits.
+ */
+struct drm_pagemap_dma_addr {
+	dma_addr_t addr;
+	u64 proto : 54;
+	u64 order : 8;
+	u64 dir : 2;
+};
+
+/**
+ * drm_pagemap_dma_addr_encode() - Encode a dma address with metadata
+ * @addr: The dma address or driver-defined address for driver private interconnects.
+ * @proto: The interconnect protocol.
+ * @order: The page order of the dma mapping. (Size is PAGE_SIZE << order).
+ * @dir: The DMA direction.
+ *
+ * Return: A struct drm_pagemap_dma_addr encoding the above information.
+ */
+static inline struct drm_pagemap_dma_addr
+drm_pagemap_dma_addr_encode(dma_addr_t addr,
+			    enum drm_interconnect_protocol proto,
+			    unsigned int order,
+			    enum dma_data_direction dir)
+{
+	return (struct drm_pagemap_dma_addr) {
+		.addr = addr,
+		.proto = proto,
+		.order = order,
+		.dir = dir,
+	};
+}
+
+/**
+ * struct drm_pagemap_ops: Ops for a drm-pagemap.
+ */
+struct drm_pagemap_ops {
+	/**
+	 * @map_dma: Map for dma access or provide a virtual address suitable for
+	 * @dev.
+	 * @dpagemap: The struct drm_pagemap for the page.
+	 * @dev: The dma mapper.
+	 * @page: The page to map.
+	 * @dir: The transfer direction.
+	 * @protocol: The protocol to use.
+	 */
+	struct drm_pagemap_dma_addr (*map_dma)(struct drm_pagemap *dpagemap,
+					       struct device *dev,
+					       struct page *page,
+					       unsigned int order,
+					       enum dma_data_direction dir);
+
+	/**
+	 * @unmap_dma: Unmap a dma address previously obtained using  @map_dma.
+	 * @dev: The dma unmapper.
+	 * @addr: The dma address obtained when mapping.
+	 */
+	void (*unmap_dma)(struct drm_pagemap *dpagemap,
+			  struct device *dev,
+			  struct drm_pagemap_dma_addr addr);
+
+};
+
+/**
+ * struct drm_pagemap: Additional information for a struct dev_pagemap
+ * used for device p2p handshaking.
+ * @ops: The struct drm_pagemap_ops.
+ * @dev: The struct drevice owning the device-private memory.
+ */
+struct drm_pagemap {
+	const struct drm_pagemap_ops *ops;
+	struct device *dev;
+};
+
+#endif