linux-kernel - [PATCH 2/3] MIPS: zboot: Add UHI semihosting debug print support

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Message-Id: <20231027182650.281405-3-jiaxun.yang@flygoat.com>
Date:   Fri, 27 Oct 2023 19:26:45 +0100
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     linux-mips@...r.kernel.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        tsbogend@...ha.franken.de, gregkh@...uxfoundation.org,
        jirislaby@...nel.org, Jiaxun Yang <jiaxun.yang@...goat.com>
Subject: [PATCH 2/3] MIPS: zboot: Add UHI semihosting debug print support

Support print debug message via MIPS UHI semihosting Plog
functions.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
---
 arch/mips/Kconfig.debug                | 11 +++++++++++
 arch/mips/boot/compressed/Makefile     |  1 +
 arch/mips/boot/compressed/dbg-uhi.c    | 11 +++++++++++
 arch/mips/boot/compressed/dbg.c        |  4 ++--
 arch/mips/boot/compressed/decompress.c |  4 ++++
 5 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 arch/mips/boot/compressed/dbg-uhi.c

diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index f4ae7900fcd3..1393bdb33f5c 100644
--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -98,6 +98,17 @@ config DEBUG_ZBOOT
 	  to reduce the kernel image size and speed up the booting procedure a
 	  little.
 
+config ZBOOT_DBG_UHI
+	bool "Enable UHI debugging"
+	depends on DEBUG_ZBOOT
+	default n
+	help
+	  Enable this option to debug compressed kernel support via UHI.
+	  Logs will be outputed to the host machine via UHI Plog function.
+	  You MUST connect system to a debugger with UHI semihosting support
+	  or use a boot montor implemented UHI exceptions, otherwise the
+	  system will hang.
+
 config ZBOOT_INGENIC_UART
 	int "UART to use for compressed kernel debugging"
 	depends on DEBUG_ZBOOT && MACH_INGENIC_SOC
diff --git a/arch/mips/boot/compressed/Makefile b/arch/mips/boot/compressed/Makefile
index 6cc28173bee8..5667597c3584 100644
--- a/arch/mips/boot/compressed/Makefile
+++ b/arch/mips/boot/compressed/Makefile
@@ -45,6 +45,7 @@ vmlinuzobjs-y := $(obj)/head.o $(obj)/decompress.o $(obj)/string.o $(obj)/bswaps
 
 ifdef CONFIG_DEBUG_ZBOOT
 vmlinuzobjs-$(CONFIG_DEBUG_ZBOOT)		   += $(obj)/dbg.o
+vmlinuzobjs-$(CONFIG_ZBOOT_DBG_UHI)		   += $(obj)/dbg-uhi.o
 vmlinuzobjs-$(CONFIG_SYS_SUPPORTS_ZBOOT_UART16550) += $(obj)/uart-16550.o
 vmlinuzobjs-$(CONFIG_SYS_SUPPORTS_ZBOOT_UART_PROM) += $(obj)/uart-prom.o
 vmlinuzobjs-$(CONFIG_MIPS_ALCHEMY)		   += $(obj)/uart-alchemy.o
diff --git a/arch/mips/boot/compressed/dbg-uhi.c b/arch/mips/boot/compressed/dbg-uhi.c
new file mode 100644
index 000000000000..7daa8de717b0
--- /dev/null
+++ b/arch/mips/boot/compressed/dbg-uhi.c
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * zboot debug output for MIPS UHI semihosting
+ */
+
+#include <asm/uhi.h>
+
+void puts(const char *s)
+{
+	uhi_plog(s, 0);
+}
diff --git a/arch/mips/boot/compressed/dbg.c b/arch/mips/boot/compressed/dbg.c
index f6728a8fd1c3..7fa5242e2b7d 100644
--- a/arch/mips/boot/compressed/dbg.c
+++ b/arch/mips/boot/compressed/dbg.c
@@ -4,7 +4,7 @@
  *
  * NOTE: putc() is board specific, if your board have a 16550 compatible uart,
  * please select SYS_SUPPORTS_ZBOOT_UART16550 for your machine. othewise, you
- * need to implement your own putc().
+ * need to implement your own putc() or puts().
  */
 #include <linux/compiler.h>
 #include <linux/types.h>
@@ -13,7 +13,7 @@ void __weak putc(char c)
 {
 }
 
-void puts(const char *s)
+void __weak puts(const char *s)
 {
 	char c;
 	while ((c = *s++) != '\0') {
diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
index c5dd415254d3..f4e69dfe2923 100644
--- a/arch/mips/boot/compressed/decompress.c
+++ b/arch/mips/boot/compressed/decompress.c
@@ -17,6 +17,7 @@
 
 #include <asm/addrspace.h>
 #include <asm/unaligned.h>
+#include <asm/uhi.h>
 #include <asm-generic/vmlinux.lds.h>
 
 /*
@@ -46,6 +47,9 @@ void error(char *x)
 	puts(x);
 	puts("\n\n -- System halted");
 
+#ifdef CONFIG_ZBOOT_DBG_UHI
+	uhi_bootfailure(0);
+#endif
 	while (1)
 		;	/* Halt */
 }
-- 
2.34.1