[PATCH 2/3] openrisc: implement C debug_ll for NS16550

[Ahmad Fatoum]

The early startup code is written in assembly, so the C DEBUG_LL
implementation isn't as useful, but it can still come in handy as
debugging aid, so let's add it.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 arch/openrisc/Kconfig                |  1 +
 arch/openrisc/include/asm/debug_ll.h | 36 ++++++++++++++++++++++++++++
 arch/openrisc/lib/board.c            |  3 +++
 common/Kconfig.debug_ll              |  4 ++++
 4 files changed, 44 insertions(+)
 create mode 100644 arch/openrisc/include/asm/debug_ll.h

diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index 4ae03b748c79..102071686e4f 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig
@@ -7,6 +7,7 @@ config OPENRISC
 	select HAVE_CONFIGURABLE_MEMORY_LAYOUT
 	select GENERIC_FIND_NEXT_BIT
 	select ARCH_HAS_SJLJ
+	select HAS_DEBUG_LL
 	default y
 
 # not used
diff --git a/arch/openrisc/include/asm/debug_ll.h b/arch/openrisc/include/asm/debug_ll.h
new file mode 100644
index 000000000000..35d436094096
--- /dev/null
+++ b/arch/openrisc/include/asm/debug_ll.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef __ASM_DEBUG_LL__
+#define __ASM_DEBUG_LL__
+
+#include <io.h>
+
+#if defined CONFIG_DEBUG_OPENRISC_NS16550
+
+#define DEBUG_LL_UART_BASE	IOMEM(0x90000000)
+
+static inline uint8_t debug_ll_read_reg(void __iomem *base, int reg)
+{
+	return readb(base + reg);
+}
+
+static inline void debug_ll_write_reg(void __iomem *base, int reg, uint8_t val)
+{
+	writeb(val, base + reg);
+}
+
+#include <debug_ll/ns16550.h>
+
+static inline void debug_ll_init(void)
+{
+	/* already configured */
+}
+
+static inline void PUTC_LL(int c)
+{
+	debug_ll_ns16550_putc(DEBUG_LL_UART_BASE, c);
+}
+
+#endif
+
+#endif
diff --git a/arch/openrisc/lib/board.c b/arch/openrisc/lib/board.c
index 9591120fee4b..c6f34ed412d7 100644
--- a/arch/openrisc/lib/board.c
+++ b/arch/openrisc/lib/board.c
@@ -18,6 +18,7 @@
 #include <init.h>
 #include <memory.h>
 #include <asm-generic/memory_layout.h>
+#include <debug_ll.h>
 
 /* Called from assembly */
 void openrisc_start_barebox(void);
@@ -27,5 +28,7 @@ void __noreturn openrisc_start_barebox(void)
 	mem_malloc_init((void *)(OPENRISC_SOPC_TEXT_BASE - MALLOC_SIZE),
 			(void *)(OPENRISC_SOPC_TEXT_BASE - 1));
 
+	putc_ll('>');
+
 	start_barebox();
 }
diff --git a/common/Kconfig.debug_ll b/common/Kconfig.debug_ll
index 3f6f3e7c3bdb..1f9255b1a45b 100644
--- a/common/Kconfig.debug_ll
+++ b/common/Kconfig.debug_ll
@@ -350,6 +350,10 @@ config DEBUG_SEMIHOSTING
 	  Say Y here if you want low-level debugging support
 	  using semihosting writec.
 
+config DEBUG_OPENRISC_NS16550
+	bool "OpenRISC NS16550 console"
+	depends on OPENRISC
+
 endchoice
 
 config DEBUG_LL_NS16550
-- 
2.39.2