swiotlb: Return physical addresses when calling swiotlb_tbl_map_single

This change makes it so that swiotlb_tbl_map_single will return a physical
address instead of a virtual address when called.  The advantage to this once
again is that we are avoiding a number of virt_to_phys and phys_to_virt
translations by working with everything as a physical address.

One change I had to make in order to support using physical addresses is that
I could no longer trust 0 to be a invalid physical address on all platforms.
So instead I made it so that ~0 is returned on error.  This should never be a
valid return value as it implies that only one byte would be available for
use.

In order to clarify things since we now have 2 physical addresses in use
inside of swiotlb_tbl_map_single I am renaming phys to orig_addr, and
dma_addr to tlb_addr.  This way is should be clear that orig_addr is
contained within io_orig_addr and tlb_addr is an address within the
io_tlb_addr buffer.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 40 insertions, 38 deletions

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index f8c0d4e1d1d3..3adc148bb8d8 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -393,12 +393,13 @@ void swiotlb_bounce(phys_addr_t phys, char *dma_addr, size_t size,
 }
 EXPORT_SYMBOL_GPL(swiotlb_bounce);
 
-void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
-                             phys_addr_t phys, size_t size,
-                             enum dma_data_direction dir)
+phys_addr_t swiotlb_tbl_map_single(struct device *hwdev,
+                                   dma_addr_t tbl_dma_addr,
+                                   phys_addr_t orig_addr, size_t size,
+                                   enum dma_data_direction dir)
 {
         unsigned long flags;
-        char *dma_addr;
+        phys_addr_t tlb_addr;
         unsigned int nslots, stride, index, wrap;
         int i;
         unsigned long mask;
@@ -462,7 +463,7 @@ void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
                                 io_tlb_list[i] = 0;
                         for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE - 1) && io_tlb_list[i]; i--)
                                 io_tlb_list[i] = ++count;
-                        dma_addr = (char *)phys_to_virt(io_tlb_start) + (index << IO_TLB_SHIFT);
+                        tlb_addr = io_tlb_start + (index << IO_TLB_SHIFT);
 
                         /*
                          * Update the indices to avoid searching in the next
@@ -480,7 +481,7 @@ void *swiotlb_tbl_map_single(struct device *hwdev, dma_addr_t tbl_dma_addr,
 
 not_found:
         spin_unlock_irqrestore(&io_tlb_lock, flags);
-        return NULL;
+        return SWIOTLB_MAP_ERROR;
 found:
         spin_unlock_irqrestore(&io_tlb_lock, flags);
 
@@ -490,11 +491,12 @@ found:
          * needed.
          */
         for (i = 0; i < nslots; i++)
-                io_tlb_orig_addr[index+i] = phys + (i << IO_TLB_SHIFT);
+                io_tlb_orig_addr[index+i] = orig_addr + (i << IO_TLB_SHIFT);
         if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
-                swiotlb_bounce(phys, dma_addr, size, DMA_TO_DEVICE);
+                swiotlb_bounce(orig_addr, phys_to_virt(tlb_addr), size,
+                               DMA_TO_DEVICE);
 
-        return dma_addr;
+        return tlb_addr;
 }
 EXPORT_SYMBOL_GPL(swiotlb_tbl_map_single);
 
@@ -502,9 +504,8 @@ EXPORT_SYMBOL_GPL(swiotlb_tbl_map_single);
  * Allocates bounce buffer and returns its kernel virtual address.
  */
 
-static void *
-map_single(struct device *hwdev, phys_addr_t phys, size_t size,
-           enum dma_data_direction dir)
+phys_addr_t map_single(struct device *hwdev, phys_addr_t phys, size_t size,
+                       enum dma_data_direction dir)
 {
         dma_addr_t start_dma_addr = phys_to_dma(hwdev, io_tlb_start);
 
@@ -598,12 +599,15 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                 dma_mask = hwdev->coherent_dma_mask;
 
         ret = (void *)__get_free_pages(flags, order);
-        if (ret && swiotlb_virt_to_bus(hwdev, ret) + size - 1 > dma_mask) {
-                /*
-                 * The allocated memory isn't reachable by the device.
-                 */
-                free_pages((unsigned long) ret, order);
-                ret = NULL;
+        if (ret) {
+                dev_addr = swiotlb_virt_to_bus(hwdev, ret);
+                if (dev_addr + size - 1 > dma_mask) {
+                        /*
+                         * The allocated memory isn't reachable by the device.
+                         */
+                        free_pages((unsigned long) ret, order);
+                        ret = NULL;
+                }
         }
         if (!ret) {
                 /*
@@ -611,13 +615,13 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                  * GFP_DMA memory; fall back on map_single(), which
                  * will grab memory from the lowest available address range.
                  */
-                ret = map_single(hwdev, 0, size, DMA_FROM_DEVICE);
-                if (!ret)
+                phys_addr_t paddr = map_single(hwdev, 0, size, DMA_FROM_DEVICE);
+                if (paddr == SWIOTLB_MAP_ERROR)
                         return NULL;
-        }
 
-        memset(ret, 0, size);
-        dev_addr = swiotlb_virt_to_bus(hwdev, ret);
+                ret = phys_to_virt(paddr);
+                dev_addr = phys_to_dma(hwdev, paddr);
+        }
 
         /* Confirm address can be DMA'd by device */
         if (dev_addr + size - 1 > dma_mask) {
@@ -629,7 +633,10 @@ swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                 swiotlb_tbl_unmap_single(hwdev, ret, size, DMA_TO_DEVICE);
                 return NULL;
         }
+
         *dma_handle = dev_addr;
+        memset(ret, 0, size);
+
         return ret;
 }
 EXPORT_SYMBOL(swiotlb_alloc_coherent);
@@ -686,9 +693,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
                             enum dma_data_direction dir,
                             struct dma_attrs *attrs)
 {
-        phys_addr_t phys = page_to_phys(page) + offset;
+        phys_addr_t map, phys = page_to_phys(page) + offset;
         dma_addr_t dev_addr = phys_to_dma(dev, phys);
-        void *map;
 
         BUG_ON(dir == DMA_NONE);
         /*
@@ -699,22 +705,18 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
         if (dma_capable(dev, dev_addr, size) && !swiotlb_force)
                 return dev_addr;
 
-        /*
-         * Oh well, have to allocate and map a bounce buffer.
-         */
+        /* Oh well, have to allocate and map a bounce buffer. */
         map = map_single(dev, phys, size, dir);
-        if (!map) {
+        if (map == SWIOTLB_MAP_ERROR) {
                 swiotlb_full(dev, size, dir, 1);
                 return phys_to_dma(dev, io_tlb_overflow_buffer);
         }
 
-        dev_addr = swiotlb_virt_to_bus(dev, map);
+        dev_addr = phys_to_dma(dev, map);
 
-        /*
-         * Ensure that the address returned is DMA'ble
-         */
+        /* Ensure that the address returned is DMA'ble */
         if (!dma_capable(dev, dev_addr, size)) {
-                swiotlb_tbl_unmap_single(dev, map, size, dir);
+                swiotlb_tbl_unmap_single(dev, phys_to_virt(map), size, dir);
                 return phys_to_dma(dev, io_tlb_overflow_buffer);
         }
 
@@ -840,9 +842,9 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
 
                 if (swiotlb_force ||
                     !dma_capable(hwdev, dev_addr, sg->length)) {
-                        void *map = map_single(hwdev, sg_phys(sg),
-                                               sg->length, dir);
-                        if (!map) {
+                        phys_addr_t map = map_single(hwdev, sg_phys(sg),
+                                                     sg->length, dir);
+                        if (map == SWIOTLB_MAP_ERROR) {
                                 /* Don't panic here, we expect map_sg users
                                    to do proper error handling. */
                                 swiotlb_full(hwdev, sg->length, dir, 0);
@@ -851,7 +853,7 @@ swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
                                 sgl[0].dma_length = 0;
                                 return 0;
                         }
-                        sg->dma_address = swiotlb_virt_to_bus(hwdev, map);
+                        sg->dma_address = phys_to_dma(hwdev, map);
                 } else
                         sg->dma_address = dev_addr;
                 sg->dma_length = sg->length;