[PATCH] bus: mvebu: fix ranges fixup

[Ezequiel Garcia <ezequiel.garcia@free-electrons.com>]

The current fixup code is slightly wrong, and only works when the
root address cell number is one.

However, Armada XP has a root address cell number of two. In this case
we are currently applying the fixup on the child high base address,
while it should be applied on the child low base address.

Fix it and add some detailed explanation to avoid having to figure this
out each time.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
---
Without this patch, the Plathome Openblocks AX3-4 board wouldn't
boot on -next. It should affect every Armada XP board that require this
fixup.

 drivers/bus/mvebu-mbus.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/bus/mvebu-mbus.c b/drivers/bus/mvebu-mbus.c
index b1e407a..b7f7836 100644
--- a/drivers/bus/mvebu-mbus.c
+++ b/drivers/bus/mvebu-mbus.c
@@ -788,6 +788,21 @@ static int mvebu_mbus_of_fixup(struct device_node *root, void *context)
 		ranges = xzalloc(lenp);
 		of_property_read_u32_array(np, "ranges", ranges, lenp/4);
 
+		/*
+		 * Iterate through each ranges tuple and fixup the custom
+		 * window ranges low base address. Because Armada XP supports
+		 * LPAE, it has 2 cells for the parent address:
+		 *   <windowid child_base high_base low_base size>
+		 *
+		 * whereas for Armada 370, there's just one:
+		 *   <windowid child_base base size>
+		 *
+		 * For instance, the following tuple:
+		 *   <MBUS_ID(0xf0, 0x01) child_base {0} base 0x100000>
+		 *
+		 * would be fixed-up like:
+		 *   <MBUS_ID(0xf0, 0x01) child_base {0} remap 0x100000>
+		 */
 		for (n = 0; n < lenp/4; n += size) {
 			struct mbus_range *r;
 			u32 mbusid = ranges[n];
@@ -797,7 +812,7 @@ static int mvebu_mbus_of_fixup(struct device_node *root, void *context)
 
 			list_for_each_entry(r, &mbus_ranges, list) {
 				if (r->mbusid == mbusid)
-					ranges[n + na] = r->remap;
+					ranges[n + na + pa - 1] = r->remap;
 			}
 		}
 
-- 
2.0.1


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