[PATCH v1 4/4] iommu/tegra: gart: Optimize map/unmap

[Dmitry Osipenko]

Currently GART writes one page entry at a time. More optimal would be to
aggregate the writes and flush BUS buffer in the end, this gives map/unmap
10-40% (depending on size of mapping) performance boost compared to a
flushing after each entry update.

Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
---
 drivers/iommu/tegra-gart.c | 63 +++++++++++++++++++++++++++++++++++-----------
 1 file changed, 48 insertions(+), 15 deletions(-)

diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c
index 4a0607669d34..9f59f5f17661 100644
--- a/drivers/iommu/tegra-gart.c
+++ b/drivers/iommu/tegra-gart.c
@@ -36,7 +36,7 @@
 #define GART_APERTURE_SIZE     SZ_32M
 
 /* bitmap of the page sizes currently supported */
-#define GART_IOMMU_PGSIZES     (SZ_4K)
+#define GART_IOMMU_PGSIZES     GENMASK(24, 12)
 
 #define GART_REG_BASE          0x24
 #define GART_CONFIG            (0x24 - GART_REG_BASE)
@@ -269,25 +269,21 @@ static void gart_iommu_domain_free(struct iommu_domain 
*domain)
        kfree(gart_domain);
 }
 
-static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova,
-                         phys_addr_t pa, size_t bytes, int prot)
+static int gart_iommu_map_page(struct gart_device *gart,
+                              unsigned long iova,
+                              phys_addr_t pa)
 {
-       struct gart_domain *gart_domain = to_gart_domain(domain);
-       struct gart_device *gart = gart_domain->gart;
        unsigned long flags;
        unsigned long pfn;
        unsigned long pte;
 
-       if (!gart_iova_range_valid(gart, iova, bytes))
-               return -EINVAL;
-
-       spin_lock_irqsave(&gart->pte_lock, flags);
        pfn = __phys_to_pfn(pa);
        if (!pfn_valid(pfn)) {
                dev_err(gart->dev, "Invalid page: %pa\n", &pa);
-               spin_unlock_irqrestore(&gart->pte_lock, flags);
                return -EINVAL;
        }
+
+       spin_lock_irqsave(&gart->pte_lock, flags);
        if (gart_debug) {
                pte = gart_read_pte(gart, iova);
                if (pte & GART_ENTRY_PHYS_ADDR_VALID) {
@@ -297,8 +293,41 @@ static int gart_iommu_map(struct iommu_domain *domain, 
unsigned long iova,
                }
        }
        gart_set_pte(gart, iova, GART_PTE(pfn));
+       spin_unlock_irqrestore(&gart->pte_lock, flags);
+
+       return 0;
+}
+
+static int gart_iommu_map(struct iommu_domain *domain, unsigned long iova,
+                         phys_addr_t pa, size_t bytes, int prot)
+{
+       struct gart_domain *gart_domain = to_gart_domain(domain);
+       struct gart_device *gart = gart_domain->gart;
+       size_t mapped;
+       int ret = -1;
+
+       if (!gart_iova_range_valid(gart, iova, bytes))
+               return -EINVAL;
+
+       for (mapped = 0; mapped < bytes; mapped += GART_PAGE_SIZE) {
+               ret = gart_iommu_map_page(gart, iova + mapped, pa + mapped);
+               if (ret)
+                       break;
+       }
+
        FLUSH_GART_REGS(gart);
+       return ret;
+}
+
+static int gart_iommu_unmap_page(struct gart_device *gart,
+                                unsigned long iova)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&gart->pte_lock, flags);
+       gart_set_pte(gart, iova, 0);
        spin_unlock_irqrestore(&gart->pte_lock, flags);
+
        return 0;
 }
 
@@ -307,16 +336,20 @@ static size_t gart_iommu_unmap(struct iommu_domain 
*domain, unsigned long iova,
 {
        struct gart_domain *gart_domain = to_gart_domain(domain);
        struct gart_device *gart = gart_domain->gart;
-       unsigned long flags;
+       size_t unmapped;
+       int ret;
 
        if (!gart_iova_range_valid(gart, iova, bytes))
                return 0;
 
-       spin_lock_irqsave(&gart->pte_lock, flags);
-       gart_set_pte(gart, iova, 0);
+       for (unmapped = 0; unmapped < bytes; unmapped += GART_PAGE_SIZE) {
+               ret = gart_iommu_unmap_page(gart, iova + unmapped);
+               if (ret)
+                       break;
+       }
+
        FLUSH_GART_REGS(gart);
-       spin_unlock_irqrestore(&gart->pte_lock, flags);
-       return bytes;
+       return unmapped;
 }
 
 static phys_addr_t gart_iommu_iova_to_phys(struct iommu_domain *domain,
-- 
2.16.3