[PATCH] arm: mvebu: Use dw-apb-uart instead of ns16650 as UART driver

[Gregory CLEMENT]

The UART controller used in the Armada 370 and Armada XP SoCs is the
Synopsys DesignWare 8250 (aka Synopsys DesignWare ABP UART). The
improper use of the ns16550 can lead to a kernel oops during boot if
a character is sent to the UART before the initialization of the
driver. The DW APB has an extra interrupt that gets raised when
writing to the LCR when busy. This explains why we need to use
dw-apb-uart driver to handle this.

Signed-off-by: Gregory CLEMENT <gregory.clement at free-electrons.com>
---

This patch fixed a bug introduced in 3.7, but as there are very few
boards supported in 3.7 (only the Armada 370 and Armada XP evaluation
boards), it is not a big deal if this patch is only applied for 3.8.

This patch is based on 3.7-rc8 and can be applied on top of the
current arm-soc/for-next with a trivial conflict on mvebu_defconfig.

---
 arch/arm/boot/dts/armada-370-xp.dtsi |    6 ++++--
 arch/arm/boot/dts/armada-xp.dtsi     |    6 ++++--
 arch/arm/configs/mvebu_defconfig     |    2 +-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/arm/boot/dts/armada-370-xp.dtsi b/arch/arm/boot/dts/armada-370-xp.dtsi
index 16cc82c..03640f7 100644
--- a/arch/arm/boot/dts/armada-370-xp.dtsi
+++ b/arch/arm/boot/dts/armada-370-xp.dtsi
@@ -44,17 +44,19 @@
 		ranges;
 
 		serial at d0012000 {
-				compatible = "ns16550";
+				compatible = "snps,dw-apb-uart";
 				reg = <0xd0012000 0x100>;
 				reg-shift = <2>;
 				interrupts = <41>;
+				reg-io-width = <4>;
 				status = "disabled";
 		};
 		serial at d0012100 {
-				compatible = "ns16550";
+				compatible = "snps,dw-apb-uart";
 				reg = <0xd0012100 0x100>;
 				reg-shift = <2>;
 				interrupts = <42>;
+				reg-io-width = <4>;
 				status = "disabled";
 		};
 
diff --git a/arch/arm/boot/dts/armada-xp.dtsi b/arch/arm/boot/dts/armada-xp.dtsi
index 71d6b5d..9a0e744 100644
--- a/arch/arm/boot/dts/armada-xp.dtsi
+++ b/arch/arm/boot/dts/armada-xp.dtsi
@@ -29,17 +29,19 @@
 
 	soc {
 		serial at d0012200 {
-				compatible = "ns16550";
+				compatible = "snps,dw-apb-uart";
 				reg = <0xd0012200 0x100>;
 				reg-shift = <2>;
 				interrupts = <43>;
+				reg-io-width = <4>;
 				status = "disabled";
 		};
 		serial at d0012300 {
-				compatible = "ns16550";
+				compatible = "snps,dw-apb-uart";
 				reg = <0xd0012300 0x100>;
 				reg-shift = <2>;
 				interrupts = <44>;
+				reg-io-width = <4>;
 				status = "disabled";
 		};
 
diff --git a/arch/arm/configs/mvebu_defconfig b/arch/arm/configs/mvebu_defconfig
index 3458752..9e34084 100644
--- a/arch/arm/configs/mvebu_defconfig
+++ b/arch/arm/configs/mvebu_defconfig
@@ -22,7 +22,7 @@ CONFIG_VFP=y
 CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
-CONFIG_SERIAL_OF_PLATFORM=y
+CONFIG_SERIAL_8250_DW=y
 CONFIG_GPIOLIB=y
 CONFIG_GPIO_SYSFS=y
 # CONFIG_USB_SUPPORT is not set
-- 
1.7.9.5