iommu: Improve the performance for direct_mapping

Currently direct_mapping always use the smallest pgsize which is SZ_4K
normally to mapping. This is unnecessary. we could gather the size, and
call iommu_map then, iommu_map could decide how to map better with the
just right pgsize.

>From the original comment, we should take care overlap, otherwise,
iommu_map may return -EEXIST. In this overlap case, we should map the
previous region before overlap firstly. then map the left part.

Each a iommu device will call this direct_mapping when its iommu
initialize, This patch is effective to improve the boot/initialization
time especially while it only needs level 1 mapping.

Signed-off-by: Anan Sun <anan.sun@mediatek.com>
Signed-off-by: Yong Wu <yong.wu@mediatek.com>
Link: https://lore.kernel.org/r/20201207093553.8635-1-yong.wu@mediatek.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index dd617ed..ae70a31 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -739,6 +739,7 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
        /* We need to consider overlapping regions for different devices */
        list_for_each_entry(entry, &mappings, list) {
                dma_addr_t start, end, addr;
+               size_t map_size = 0;
 
                if (domain->ops->apply_resv_region)
                        domain->ops->apply_resv_region(dev, domain, entry);
@@ -750,16 +751,27 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
                    entry->type != IOMMU_RESV_DIRECT_RELAXABLE)
                        continue;
 
-               for (addr = start; addr < end; addr += pg_size) {
+               for (addr = start; addr <= end; addr += pg_size) {
                        phys_addr_t phys_addr;
 
+                       if (addr == end)
+                               goto map_end;
+
                        phys_addr = iommu_iova_to_phys(domain, addr);
-                       if (phys_addr)
+                       if (!phys_addr) {
+                               map_size += pg_size;
                                continue;
+                       }
 
-                       ret = iommu_map(domain, addr, addr, pg_size, entry->prot);
-                       if (ret)
-                               goto out;
+map_end:
+                       if (map_size) {
+                               ret = iommu_map(domain, addr - map_size,
+                                               addr - map_size, map_size,
+                                               entry->prot);
+                               if (ret)
+                                       goto out;
+                               map_size = 0;
+                       }
                }
 
        }