[PATCH v2 12/25] of/address: Add infrastructure to declare MMIO as non-posted

Hector Martin
2021-02-15T12:21:46Z

This implements the 'nonposted-mmio' and 'posted-mmio' boolean
properties. Placing these properties in a bus marks all child devices as
requiring non-posted or posted MMIO mappings. If no such properties are
found, the default is posted MMIO.

of_mmio_is_nonposted() performs the tree walking 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 Apple ARM platforms, as an
optimization.

Signed-off-by: Hector Martin <marcan@marcan.st>
---
drivers/of/address.c | 72 ++++++++++++++++++++++++++++++++++++--
include/linux/of_address.h | 1 +
2 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 73ddf2540f3f..6114dceb1ba6 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -847,6 +847,9 @@ 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 +899,10 @@ 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 +934,11 @@ 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 +1104,61 @@ bool of_dma_is_coherent(struct device_node *np)
return false;
}
EXPORT_SYMBOL_GPL(of_dma_is_coherent);
+
+static bool of_nonposted_mmio_quirk(void)
+{
+ if (IS_ENABLED(CONFIG_ARCH_APPLE)) {
+ /* To save cycles, we cache the result for global "Apple ARM" setting */
+ static int quirk_state = -1;
+
+ /* Make quirk cached */
+ if (quirk_state < 0)
+ quirk_state = of_machine_is_compatible("apple,arm-platform");
+ return !!quirk_state;
+ }
+ return false;
+}
+
+/**
+ * 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 or a parent. "posted-mmio" has the opposite
+ * effect, terminating recursion and overriding any
+ * "nonposted-mmio" properties in parent buses.
+ *
+ * Recursion terminates if reach a non-translatable boundary
+ * (a node without a 'ranges' property).
+ *
+ * This is currently only enabled on Apple ARM devices, as an
+ * optimization.
+ */
+bool of_mmio_is_nonposted(struct device_node *np)
+{
+ struct device_node *node;
+ struct device_node *parent;
+
+ if (!of_nonposted_mmio_quirk())
+ return false;
+
+ node = of_get_parent(np);
+
+ while (node) {
+ if (!of_property_read_bool(node, "ranges")) {
+ break;
+ } else if (of_property_read_bool(node, "nonposted-mmio")) {
+ of_node_put(node);
+ return true;
+ } else if (of_property_read_bool(node, "posted-mmio")) {
+ break;
+ }
+ parent = of_get_parent(node);
+ of_node_put(node);
+ node = parent;
+ }
+
+ of_node_put(node);
+ return false;
+}
+EXPORT_SYMBOL_GPL(of_mmio_is_nonposted);
diff --git a/include/linux/of_address.h b/include/linux/of_address.h
index 88bc943405cd..88f6333fee6c 100644
--- a/include/linux/of_address.h
+++ b/include/linux/of_address.h
@@ -62,6 +62,7 @@ extern struct of_pci_range *of_pci_range_parser_one(
struct of_pci_range_parser *parser,
struct of_pci_range *range);
extern bool of_dma_is_coherent(struct device_node *np);
+extern bool of_mmio_is_nonposted(struct device_node *np);
#else /* CONFIG_OF_ADDRESS */
static inline void __iomem *of_io_request_and_map(struct device_node *device,
int index, const char *name)
--
2.30.0