[PATCH RFC 05/10] ARM: debug: Add Cortina Systems CS75xx UART0 support

[Fil Dunsky via B4 Relay <devnull+filipp.dunsky.gmail.com@kernel.org>]

From: Fil Dunsky <filipp.dunsky@gmail.com>

Add low-level debug output through UART0 of the Cortina Systems CS75xx
SoCs. The UART is mapped at a fixed virtual address by the generic
debug_ll_io_init(), so no platform map_io is needed.

Signed-off-by: Fil Dunsky <filipp.dunsky@gmail.com>
---
 arch/arm/Kconfig.debug          | 16 ++++++++++++++--
 arch/arm/include/debug/cs75xx.S | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index abcf14f1027..61cd64fc152 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -308,6 +308,15 @@ choice
 		  Say Y here if you want the debug print routines to direct
 		  their output to the second serial port on these devices.
 
+	config DEBUG_CS75XX_UART0
+		bool "Kernel low-level debugging messages via CS75xx UART0"
+		depends on ARCH_CORTINA_CS75XX
+		help
+		  Say Y here if you want the debug print routines to direct
+		  their output to UART0 of Cortina Systems CS75xx SoCs. This
+		  is the console port on the Securifi Almond+. The UART is
+		  expected to be set up by the bootloader.
+
 	config DEBUG_DAVINCI_DA8XX_UART1
 		bool "Kernel low-level debugging on DaVinci DA8XX using UART1"
 		depends on ARCH_DAVINCI_DA8XX
@@ -1531,6 +1540,7 @@ config DEBUG_LL_INCLUDE
 	default "debug/vt8500.S" if DEBUG_VT8500_UART0
 	default "debug/zynq.S" if DEBUG_ZYNQ_UART0 || DEBUG_ZYNQ_UART1
 	default "debug/bcm63xx.S" if DEBUG_BCM63XX_UART || DEBUG_BCMBCA
+	default "debug/cs75xx.S" if DEBUG_CS75XX_UART0
 	default "debug/digicolor.S" if DEBUG_DIGICOLOR_UA0
 	default "debug/brcmstb.S" if DEBUG_BRCMSTB_UART
 	default "mach/debug-macro.S"
@@ -1632,6 +1642,7 @@ config DEBUG_UART_PHYS
 	default 0xe8008000 if DEBUG_R7S72100_SCIF2 || DEBUG_R7S9210_SCIF2
 	default 0xe8009000 if DEBUG_R7S9210_SCIF4
 	default 0xf0000000 if DEBUG_DIGICOLOR_UA0
+	default 0xf0070110 if DEBUG_CS75XX_UART0
 	default 0xf1012000 if DEBUG_MVEBU_UART0_ALTERNATE
 	default 0xf1012100 if DEBUG_MVEBU_UART1_ALTERNATE
 	default 0xf7fc9000 if DEBUG_BERLIN_UART
@@ -1670,7 +1681,7 @@ config DEBUG_UART_PHYS
 		DEBUG_RMOBILE_SCIFA4 || \
 		DEBUG_S3C64XX_UART || \
 		DEBUG_BCM63XX_UART || DEBUG_BCMBCA || DEBUG_ASM9260_UART || \
-		DEBUG_DIGICOLOR_UA0 || \
+		DEBUG_CS75XX_UART0 || DEBUG_DIGICOLOR_UA0 || \
 		DEBUG_AT91_UART || DEBUG_STM32_UART || \
 		DEBUG_STIH41X_ASC2 || DEBUG_STIH41X_SBC_ASC1 || \
 		DEBUG_STIH418_SBC_ASC0
@@ -1708,6 +1719,7 @@ config DEBUG_UART_VIRT
 	default 0xf7000800 if DEBUG_S3C64XX_UART && DEBUG_S3C_UART2
 	default 0xf7000c00 if DEBUG_S3C64XX_UART && DEBUG_S3C_UART3
 	default 0xf7020000 if DEBUG_AT91_SAMA5D2_UART1
+	default 0xf7070110 if DEBUG_CS75XX_UART0
 	default 0xf7fc9000 if DEBUG_BERLIN_UART
 	default 0xf8007000 if DEBUG_HIP04_UART
 	default 0xf8009000 if DEBUG_VEXPRESS_UART0_CA9
@@ -1772,7 +1784,7 @@ config DEBUG_UART_VIRT
 		DEBUG_QCOM_UARTDM || \
 		DEBUG_S3C64XX_UART || \
 		DEBUG_BCM63XX_UART || DEBUG_BCMBCA || DEBUG_ASM9260_UART || \
-		DEBUG_DIGICOLOR_UA0 || \
+		DEBUG_CS75XX_UART0 || DEBUG_DIGICOLOR_UA0 || \
 		DEBUG_AT91_UART || DEBUG_STM32_UART || \
 		DEBUG_STIH41X_ASC2 || DEBUG_STIH41X_SBC_ASC1 || \
 		DEBUG_STIH418_SBC_ASC0
diff --git a/arch/arm/include/debug/cs75xx.S b/arch/arm/include/debug/cs75xx.S
new file mode 100644
index 00000000000..d840384cc32
--- /dev/null
+++ b/arch/arm/include/debug/cs75xx.S
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Debugging macro include header for the Cortina Systems CS75xx UART
+ */
+
+#define CS75XX_UART_TXDAT		0x10
+#define CS75XX_UART_INFO		0x18
+#define CS75XX_UART_INFO_TX_FULL	(1 << 2)
+#define CS75XX_UART_INFO_TX_EMPTY	(1 << 3)
+
+		.macro	addruart, rp, rv, tmp
+		ldr	\rp, =CONFIG_DEBUG_UART_PHYS
+		ldr	\rv, =CONFIG_DEBUG_UART_VIRT
+		.endm
+
+		.macro	senduart, rd, rx
+		ARM_BE8(rev \rd, \rd)
+		str	\rd, [\rx, #CS75XX_UART_TXDAT]
+		.endm
+
+		.macro	waituartcts, rd, rx
+		.endm
+
+		.macro	waituarttxrdy, rd, rx
+1001:		ldr	\rd, [\rx, #CS75XX_UART_INFO]
+		ARM_BE8(rev \rd, \rd)
+		tst	\rd, #CS75XX_UART_INFO_TX_FULL
+		bne	1001b
+		.endm
+
+		.macro	busyuart, rd, rx
+1002:		ldr	\rd, [\rx, #CS75XX_UART_INFO]
+		ARM_BE8(rev \rd, \rd)
+		tst	\rd, #CS75XX_UART_INFO_TX_EMPTY
+		beq	1002b
+		.endm

-- 
2.53.0