of/address: Add infrastructure to declare MMIO as non-posted

This implements the 'nonposted-mmio' boolean property. Placing this
property in a bus marks all direct child devices as requiring
non-posted MMIO mappings. If no such property is found, the default
is posted MMIO.

of_mmio_is_nonposted() performs this check to determine if a given
device has requested non-posted MMIO.

of_address_to_resource() uses this to set the IORESOURCE_MEM_NONPOSTED
flag on resources that require non-posted MMIO.

of_iomap() and of_io_request_and_map() then use this flag to pick the
correct ioremap() variant.

This mechanism is currently restricted to builds that support Apple ARM
platforms, as an optimization.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 73ddf25..a2373fa 100644 (file)
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -26,6 +26,7 @@ static struct of_bus *of_match_bus(struct device_node *np);
 static int __of_address_to_resource(struct device_node *dev,
                const __be32 *addrp, u64 size, unsigned int flags,
                const char *name, struct resource *r);
+static bool of_mmio_is_nonposted(struct device_node *np);
 
 /* Debug utility */
 #ifdef DEBUG
@@ -847,6 +848,9 @@ static int __of_address_to_resource(struct device_node *dev,
                return -EINVAL;
        memset(r, 0, sizeof(struct resource));
 
+       if (of_mmio_is_nonposted(dev))
+               flags |= IORESOURCE_MEM_NONPOSTED;
+
        r->start = taddr;
        r->end = taddr + size - 1;
        r->flags = flags;
@@ -896,7 +900,10 @@ void __iomem *of_iomap(struct device_node *np, int index)
        if (of_address_to_resource(np, index, &res))
                return NULL;
 
-       return ioremap(res.start, resource_size(&res));
+       if (res.flags & IORESOURCE_MEM_NONPOSTED)
+               return ioremap_np(res.start, resource_size(&res));
+       else
+               return ioremap(res.start, resource_size(&res));
 }
 EXPORT_SYMBOL(of_iomap);
 
@@ -928,7 +935,11 @@ void __iomem *of_io_request_and_map(struct device_node *np, int index,
        if (!request_mem_region(res.start, resource_size(&res), name))
                return IOMEM_ERR_PTR(-EBUSY);
 
-       mem = ioremap(res.start, resource_size(&res));
+       if (res.flags & IORESOURCE_MEM_NONPOSTED)
+               mem = ioremap_np(res.start, resource_size(&res));
+       else
+               mem = ioremap(res.start, resource_size(&res));
+
        if (!mem) {
                release_mem_region(res.start, resource_size(&res));
                return IOMEM_ERR_PTR(-ENOMEM);
@@ -1094,3 +1105,31 @@ bool of_dma_is_coherent(struct device_node *np)
        return false;
 }
 EXPORT_SYMBOL_GPL(of_dma_is_coherent);
+
+/**
+ * of_mmio_is_nonposted - Check if device uses non-posted MMIO
+ * @np:        device node
+ *
+ * Returns true if the "nonposted-mmio" property was found for
+ * the device's bus.
+ *
+ * This is currently only enabled on builds that support Apple ARM devices, as
+ * an optimization.
+ */
+static bool of_mmio_is_nonposted(struct device_node *np)
+{
+       struct device_node *parent;
+       bool nonposted;
+
+       if (!IS_ENABLED(CONFIG_ARCH_APPLE))
+               return false;
+
+       parent = of_get_parent(np);
+       if (!parent)
+               return false;
+
+       nonposted = of_property_read_bool(parent, "nonposted-mmio");
+
+       of_node_put(parent);
+       return nonposted;
+}