[PATCH v4 3/4] drm/pagemap: Split drm_pagemap_migrate_map_pages into device / system

[Matthew Brost <matthew.brost@intel.com>]

Split drm_pagemap_migrate_map_pages into device / system helpers clearly
seperating these operations. Will help with upcoming changes to split
IOVA allocation steps.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/drm_pagemap.c | 146 ++++++++++++++++++++++------------
 1 file changed, 96 insertions(+), 50 deletions(-)

diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
index fbd69f383457..29677b19bb69 100644
--- a/drivers/gpu/drm/drm_pagemap.c
+++ b/drivers/gpu/drm/drm_pagemap.c
@@ -205,7 +205,7 @@ static void drm_pagemap_get_devmem_page(struct page *page,
 }
 
 /**
- * drm_pagemap_migrate_map_pages() - Map migration pages for GPU SVM migration
+ * drm_pagemap_migrate_map_device_pages() - Map device migration pages for GPU SVM migration
  * @dev: The device performing the migration.
  * @local_dpagemap: The drm_pagemap local to the migrating device.
  * @pagemap_addr: Array to store DMA information corresponding to mapped pages.
@@ -221,19 +221,22 @@ static void drm_pagemap_get_devmem_page(struct page *page,
  *
  * Returns: 0 on success, -EFAULT if an error occurs during mapping.
  */
-static int drm_pagemap_migrate_map_pages(struct device *dev,
-					 struct drm_pagemap *local_dpagemap,
-					 struct drm_pagemap_addr *pagemap_addr,
-					 unsigned long *migrate_pfn,
-					 unsigned long npages,
-					 enum dma_data_direction dir,
-					 const struct drm_pagemap_migrate_details *mdetails)
+static int
+drm_pagemap_migrate_map_device_pages(struct device *dev,
+				     struct drm_pagemap *local_dpagemap,
+				     struct drm_pagemap_addr *pagemap_addr,
+				     unsigned long *migrate_pfn,
+				     unsigned long npages,
+				     enum dma_data_direction dir,
+				     const struct drm_pagemap_migrate_details *mdetails)
 {
 	unsigned long num_peer_pages = 0, num_local_pages = 0, i;
 
 	for (i = 0; i < npages;) {
 		struct page *page = migrate_pfn_to_page(migrate_pfn[i]);
-		dma_addr_t dma_addr;
+		struct drm_pagemap_zdd *zdd;
+		struct drm_pagemap *dpagemap;
+		struct drm_pagemap_addr addr;
 		struct folio *folio;
 		unsigned int order = 0;
 
@@ -243,36 +246,26 @@ static int drm_pagemap_migrate_map_pages(struct device *dev,
 		folio = page_folio(page);
 		order = folio_order(folio);
 
-		if (is_device_private_page(page)) {
-			struct drm_pagemap_zdd *zdd = drm_pagemap_page_zone_device_data(page);
-			struct drm_pagemap *dpagemap = zdd->dpagemap;
-			struct drm_pagemap_addr addr;
-
-			if (dpagemap == local_dpagemap) {
-				if (!mdetails->can_migrate_same_pagemap)
-					goto next;
+		WARN_ON_ONCE(!is_device_private_page(page));
 
-				num_local_pages += NR_PAGES(order);
-			} else {
-				num_peer_pages += NR_PAGES(order);
-			}
+		zdd = drm_pagemap_page_zone_device_data(page);
+		dpagemap = zdd->dpagemap;
 
-			addr = dpagemap->ops->device_map(dpagemap, dev, page, order, dir);
-			if (dma_mapping_error(dev, addr.addr))
-				return -EFAULT;
+		if (dpagemap == local_dpagemap) {
+			if (!mdetails->can_migrate_same_pagemap)
+				goto next;
 
-			pagemap_addr[i] = addr;
+			num_local_pages += NR_PAGES(order);
 		} else {
-			dma_addr = dma_map_page(dev, page, 0, page_size(page), dir);
-			if (dma_mapping_error(dev, dma_addr))
-				return -EFAULT;
-
-			pagemap_addr[i] =
-				drm_pagemap_addr_encode(dma_addr,
-							DRM_INTERCONNECT_SYSTEM,
-							order, dir);
+			num_peer_pages += NR_PAGES(order);
 		}
 
+		addr = dpagemap->ops->device_map(dpagemap, dev, page, order, dir);
+		if (dma_mapping_error(dev, addr.addr))
+			return -EFAULT;
+
+		pagemap_addr[i] = addr;
+
 next:
 		i += NR_PAGES(order);
 	}
@@ -287,6 +280,59 @@ static int drm_pagemap_migrate_map_pages(struct device *dev,
 	return 0;
 }
 
+/**
+ * drm_pagemap_migrate_map_system_pages() - Map system migration pages for GPU SVM migration
+ * @dev: The device performing the migration.
+ * @pagemap_addr: Array to store DMA information corresponding to mapped pages.
+ * @migrate_pfn: Array of page frame numbers of system pages or peer pages to map.
+ * @npages: Number of system pages or peer pages to map.
+ * @dir: Direction of data transfer (e.g., DMA_BIDIRECTIONAL)
+ *
+ * This function maps pages of memory for migration usage in GPU SVM. It
+ * iterates over each page frame number provided in @migrate_pfn, maps the
+ * corresponding page, and stores the DMA address in the provided @dma_addr
+ * array.
+ *
+ * Returns: 0 on success, -EFAULT if an error occurs during mapping.
+ */
+static int
+drm_pagemap_migrate_map_system_pages(struct device *dev,
+				     struct drm_pagemap_addr *pagemap_addr,
+				     unsigned long *migrate_pfn,
+				     unsigned long npages,
+				     enum dma_data_direction dir)
+{
+	unsigned long i;
+
+	for (i = 0; i < npages;) {
+		struct page *page = migrate_pfn_to_page(migrate_pfn[i]);
+		dma_addr_t dma_addr;
+		struct folio *folio;
+		unsigned int order = 0;
+
+		if (!page)
+			goto next;
+
+		WARN_ON_ONCE(is_device_private_page(page));
+		folio = page_folio(page);
+		order = folio_order(folio);
+
+		dma_addr = dma_map_page(dev, page, 0, page_size(page), dir);
+		if (dma_mapping_error(dev, dma_addr))
+			return -EFAULT;
+
+		pagemap_addr[i] =
+			drm_pagemap_addr_encode(dma_addr,
+						DRM_INTERCONNECT_SYSTEM,
+						order, dir);
+
+next:
+		i += NR_PAGES(order);
+	}
+
+	return 0;
+}
+
 /**
  * drm_pagemap_migrate_unmap_pages() - Unmap pages previously mapped for GPU SVM migration
  * @dev: The device for which the pages were mapped
@@ -347,9 +393,11 @@ drm_pagemap_migrate_remote_to_local(struct drm_pagemap_devmem *devmem,
 				    const struct drm_pagemap_migrate_details *mdetails)
 
 {
-	int err = drm_pagemap_migrate_map_pages(remote_device, remote_dpagemap,
-						pagemap_addr, local_pfns,
-						npages, DMA_FROM_DEVICE, mdetails);
+	int err = drm_pagemap_migrate_map_device_pages(remote_device,
+						       remote_dpagemap,
+						       pagemap_addr, local_pfns,
+						       npages, DMA_FROM_DEVICE,
+						       mdetails);
 
 	if (err)
 		goto out;
@@ -368,12 +416,11 @@ drm_pagemap_migrate_sys_to_dev(struct drm_pagemap_devmem *devmem,
 			       struct page *local_pages[],
 			       struct drm_pagemap_addr pagemap_addr[],
 			       unsigned long npages,
-			       const struct drm_pagemap_devmem_ops *ops,
-			       const struct drm_pagemap_migrate_details *mdetails)
+			       const struct drm_pagemap_devmem_ops *ops)
 {
-	int err = drm_pagemap_migrate_map_pages(devmem->dev, devmem->dpagemap,
-						pagemap_addr, sys_pfns, npages,
-						DMA_TO_DEVICE, mdetails);
+	int err = drm_pagemap_migrate_map_system_pages(devmem->dev,
+						       pagemap_addr, sys_pfns,
+						       npages, DMA_TO_DEVICE);
 
 	if (err)
 		goto out;
@@ -437,7 +484,7 @@ static int drm_pagemap_migrate_range(struct drm_pagemap_devmem *devmem,
 						     &pages[last->start],
 						     &pagemap_addr[last->start],
 						     cur->start - last->start,
-						     last->ops, mdetails);
+						     last->ops);
 
 out:
 	*last = *cur;
@@ -954,7 +1001,6 @@ EXPORT_SYMBOL(drm_pagemap_put);
 int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
 {
 	const struct drm_pagemap_devmem_ops *ops = devmem_allocation->ops;
-	struct drm_pagemap_migrate_details mdetails = {};
 	unsigned long npages, mpages = 0;
 	struct page **pages;
 	unsigned long *src, *dst;
@@ -993,10 +1039,10 @@ int drm_pagemap_evict_to_ram(struct drm_pagemap_devmem *devmem_allocation)
 	if (err || !mpages)
 		goto err_finalize;
 
-	err = drm_pagemap_migrate_map_pages(devmem_allocation->dev,
-					    devmem_allocation->dpagemap, pagemap_addr,
-					    dst, npages, DMA_FROM_DEVICE,
-					    &mdetails);
+	err = drm_pagemap_migrate_map_system_pages(devmem_allocation->dev,
+						   pagemap_addr,
+						   dst, npages,
+						   DMA_FROM_DEVICE);
 	if (err)
 		goto err_finalize;
 
@@ -1057,7 +1103,6 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
 		MIGRATE_VMA_SELECT_DEVICE_COHERENT,
 		.fault_page	= page,
 	};
-	struct drm_pagemap_migrate_details mdetails = {};
 	struct drm_pagemap_zdd *zdd;
 	const struct drm_pagemap_devmem_ops *ops;
 	struct device *dev = NULL;
@@ -1115,8 +1160,9 @@ static int __drm_pagemap_migrate_to_ram(struct vm_area_struct *vas,
 	if (err)
 		goto err_finalize;
 
-	err = drm_pagemap_migrate_map_pages(dev, zdd->dpagemap, pagemap_addr, migrate.dst, npages,
-					    DMA_FROM_DEVICE, &mdetails);
+	err = drm_pagemap_migrate_map_system_pages(dev, pagemap_addr,
+						   migrate.dst, npages,
+						   DMA_FROM_DEVICE);
 	if (err)
 		goto err_finalize;
 
-- 
2.34.1