OF: Simplify DMA range calculations

Juggling start, end, and size values for a range is somewhat redundant
and a little hard to follow. Consolidate down to just using inclusive
start and end, which saves us worrying about size overflows for full
64-bit ranges (note that passing a potentially-overflowed value through
to arch_setup_dma_ops() is benign for all current implementations, and
this is working towards removing that anyway).

Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/3e0a72fe3d79eae660e4284bb32f2cb39868ccd7.1713523152.git.robin.murphy@arm.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/of/device.c b/drivers/of/device.c
index a988bee2ee5ad17d16d5998a33d0657f0703b807..841ccd3a19d1eac10fef7b9fccf2d699bd295e2c 100644 (file)
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -96,7 +96,7 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
        const struct bus_dma_region *map = NULL;
        struct device_node *bus_np;
        u64 dma_start = 0;
-       u64 mask, end, size = 0;
+       u64 mask, end = 0;
        bool coherent;
        int iommu_ret;
        int ret;
@@ -118,17 +118,15 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
                        return ret == -ENODEV ? 0 : ret;
        } else {
                const struct bus_dma_region *r = map;
-               u64 dma_end = 0;
 
                /* Determine the overall bounds of all DMA regions */
                for (dma_start = ~0; r->size; r++) {
                        /* Take lower and upper limits */
                        if (r->dma_start < dma_start)
                                dma_start = r->dma_start;
-                       if (r->dma_start + r->size > dma_end)
-                               dma_end = r->dma_start + r->size;
+                       if (r->dma_start + r->size > end)
+                               end = r->dma_start + r->size;
                }
-               size = dma_end - dma_start;
        }
 
        /*
@@ -142,16 +140,15 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
                dev->dma_mask = &dev->coherent_dma_mask;
        }
 
-       if (!size && dev->coherent_dma_mask)
-               size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
-       else if (!size)
-               size = 1ULL << 32;
+       if (!end && dev->coherent_dma_mask)
+               end = dev->coherent_dma_mask;
+       else if (!end)
+               end = (1ULL << 32) - 1;
 
        /*
         * Limit coherent and dma mask based on size and default mask
         * set by the driver.
         */
-       end = dma_start + size - 1;
        mask = DMA_BIT_MASK(ilog2(end) + 1);
        dev->coherent_dma_mask &= mask;
        *dev->dma_mask &= mask;
@@ -185,7 +182,7 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
        } else
                dev_dbg(dev, "device is behind an iommu\n");
 
-       arch_setup_dma_ops(dev, dma_start, size, coherent);
+       arch_setup_dma_ops(dev, dma_start, end - dma_start + 1, coherent);
 
        if (iommu_ret)
                of_dma_set_restricted_buffer(dev, np);