powerpc/pseries/iommu: Allow DDW windows starting at 0x00

enable_ddw() currently returns the address of the DMA window, which is
considered invalid if has the value 0x00.

Also, it only considers valid an address returned from find_existing_ddw
if it's not 0x00.

Changing this behavior makes sense, given the users of enable_ddw() only
need to know if direct mapping is possible. It can also allow a DMA window
starting at 0x00 to be used.

This will be helpful for using a DDW with indirect mapping, as the window
address will be different than 0x00, but it will not map the whole
partition.

Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210817063929.38701-6-leobras.c@gmail.com

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 712d166..b34b473 100644 (file)
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -853,25 +853,26 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
                        np, ret);
 }
 
-static u64 find_existing_ddw(struct device_node *pdn, int *window_shift)
+static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr, int *window_shift)
 {
        struct direct_window *window;
        const struct dynamic_dma_window_prop *direct64;
-       u64 dma_addr = 0;
+       bool found = false;
 
        spin_lock(&direct_window_list_lock);
        /* check if we already created a window and dupe that config if so */
        list_for_each_entry(window, &direct_window_list, list) {
                if (window->device == pdn) {
                        direct64 = window->prop;
-                       dma_addr = be64_to_cpu(direct64->dma_base);
+                       *dma_addr = be64_to_cpu(direct64->dma_base);
                        *window_shift = be32_to_cpu(direct64->window_shift);
+                       found = true;
                        break;
                }
        }
        spin_unlock(&direct_window_list_lock);
 
-       return dma_addr;
+       return found;
 }
 
 static struct direct_window *ddw_list_new_entry(struct device_node *pdn,
@@ -1161,20 +1162,20 @@ static int iommu_get_page_shift(u32 query_page_size)
  * pdn: the parent pe node with the ibm,dma_window property
  * Future: also check if we can remap the base window for our base page size
  *
- * returns the dma offset for use by the direct mapped DMA code.
+ * returns true if can map all pages (direct mapping), false otherwise..
  */
-static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
+static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 {
        int len = 0, ret;
        int max_ram_len = order_base_2(ddw_memory_hotplug_max());
        struct ddw_query_response query;
        struct ddw_create_response create;
        int page_shift;
-       u64 dma_addr;
        struct device_node *dn;
        u32 ddw_avail[DDW_APPLICABLE_SIZE];
        struct direct_window *window;
        struct property *win64;
+       bool ddw_enabled = false;
        struct dynamic_dma_window_prop *ddwprop;
        struct failed_ddw_pdn *fpdn;
        bool default_win_removed = false;
@@ -1186,9 +1187,10 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 
        mutex_lock(&direct_window_init_mutex);
 
-       dma_addr = find_existing_ddw(pdn, &len);
-       if (dma_addr != 0)
+       if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset, &len)) {
+               ddw_enabled = true;
                goto out_unlock;
+       }
 
        /*
         * If we already went through this for a previous function of
@@ -1342,7 +1344,8 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
        list_add(&window->list, &direct_window_list);
        spin_unlock(&direct_window_list_lock);
 
-       dma_addr = be64_to_cpu(ddwprop->dma_base);
+       dev->dev.archdata.dma_offset = be64_to_cpu(ddwprop->dma_base);
+       ddw_enabled = true;
        goto out_unlock;
 
 out_free_window:
@@ -1374,10 +1377,10 @@ out_unlock:
         * as RAM, then we failed to create a window to cover persistent
         * memory and need to set the DMA limit.
         */
-       if (pmem_present && dma_addr && (len == max_ram_len))
-               dev->dev.bus_dma_limit = dma_addr + (1ULL << len);
+       if (pmem_present && ddw_enabled && (len == max_ram_len))
+               dev->dev.bus_dma_limit = dev->dev.archdata.dma_offset + (1ULL << len);
 
-       return dma_addr;
+       return ddw_enabled;
 }
 
 static void pci_dma_dev_setup_pSeriesLP(struct pci_dev *dev)
@@ -1456,11 +1459,8 @@ static bool iommu_bypass_supported_pSeriesLP(struct pci_dev *pdev, u64 dma_mask)
                        break;
        }
 
-       if (pdn && PCI_DN(pdn)) {
-               pdev->dev.archdata.dma_offset = enable_ddw(pdev, pdn);
-               if (pdev->dev.archdata.dma_offset)
-                       return true;
-       }
+       if (pdn && PCI_DN(pdn))
+               return enable_ddw(pdev, pdn);
 
        return false;
 }