[PATCH] arm: a37xx: Remap IO space to bus address 0x0

["Pali Rohár" <pali@kernel.org>]

Remap PCI I/O space to the bus address 0x0 in the Armada 37xx device-tree
in order to support legacy I/O port based cards which have hardcoded I/O
ports in low address space.

Some legacy PCI I/O based cards do not support 32-bit I/O addressing.

Signed-off-by: Pali Rohár <pali@kernel.org>

---
Same change was sent to linux kernel:
https://lore.kernel.org/linux-arm-kernel/20220304163027.29357-1-pali@kernel.org/
---
 arch/arm/dts/armada-3720-turris-mox.dts | 7 ++++++-
 arch/arm/dts/armada-37xx.dtsi           | 2 +-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/dts/armada-3720-turris-mox.dts b/arch/arm/dts/armada-3720-turris-mox.dts
index 1fc4a30d03e7..595b4b5abba0 100644
--- a/arch/arm/dts/armada-3720-turris-mox.dts
+++ b/arch/arm/dts/armada-3720-turris-mox.dts
@@ -139,7 +139,9 @@
 	/*
 	 * U-Boot port for Turris Mox has a bug which always expects that "ranges" DT property
 	 * contains exactly 2 ranges with 3 (child) address cells, 2 (parent) address cells and
-	 * 2 size cells and also expects that the second range starts at 16 MB offset. If these
+	 * 2 size cells and also expects that the second range starts at 16 MB offset. Also it
+	 * expects that first range uses same address for PCI (child) and CPU (parent) cells (so
+	 * no remapping) and that this address is the lowest from all specified ranges. If these
 	 * conditions are not met then U-Boot crashes during loading kernel DTB file. PCIe address
 	 * space is 128 MB long, so the best split between MEM and IO is to use fixed 16 MB window
 	 * for IO and the rest 112 MB (64+32+16) for MEM. Controller supports 32-bit IO mapping.
@@ -148,6 +150,9 @@
 	 * https://source.denx.de/u-boot/u-boot/-/commit/cb2ddb291ee6fcbddd6d8f4ff49089dfe580f5d7
 	 * https://source.denx.de/u-boot/u-boot/-/commit/c64ac3b3185aeb3846297ad7391fc6df8ecd73bf
 	 * https://source.denx.de/u-boot/u-boot/-/commit/4a82fca8e330157081fc132a591ebd99ba02ee33
+	 * Bug related to requirement of same child and parent addresses for first range is fixed
+	 * in U-Boot version 2022.04 by following commit:
+	 * https://source.denx.de/u-boot/u-boot/-/commit/1fd54253bca7d43d046bba4853fe5fafd034bc17
 	 */
 	#address-cells = <3>;
 	#size-cells = <2>;
diff --git a/arch/arm/dts/armada-37xx.dtsi b/arch/arm/dts/armada-37xx.dtsi
index 9fa6457facb8..0bb4f607630a 100644
--- a/arch/arm/dts/armada-37xx.dtsi
+++ b/arch/arm/dts/armada-37xx.dtsi
@@ -499,7 +499,7 @@
 			 * (totaling 127 MiB) for MEM.
 			 */
 			ranges = <0x82000000 0 0xe8000000   0 0xe8000000   0 0x07f00000   /* Port 0 MEM */
-				  0x81000000 0 0xeff00000   0 0xeff00000   0 0x00100000>; /* Port 0 IO*/
+				  0x81000000 0 0x00000000   0 0xeff00000   0 0x00100000>; /* Port 0 IO */
 			interrupt-map-mask = <0 0 0 7>;
 			interrupt-map = <0 0 0 1 &pcie_intc 0>,
 					<0 0 0 2 &pcie_intc 1>,
-- 
2.20.1