[PATCH v3 02/10] RISC-V: make it possible to run nmon from PBL C code

[Antony Pavlov]

After migrating to PBL we can't use nmon assembler macro
in C code anymore. Some changes are introduced to invoke
nmon from PBL C code:

  * use 'lla' macro instruction instead of 'la';
  * don't touch the 'ra' register, use 'a2' instead;
  * add wrapper C function for nmon.

Signed-off-by: Antony Pavlov <antonynpavlov at gmail.com>
Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 arch/riscv/boot/Makefile            |  1 +
 arch/riscv/boot/nmon_entry.S        | 13 ++++++++
 arch/riscv/include/asm/riscv_nmon.h | 49 +++++++++++++++++++----------
 3 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
index 968a826d16..80f63a4a0a 100644
--- a/arch/riscv/boot/Makefile
+++ b/arch/riscv/boot/Makefile
@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-y += start.o
 pbl-y += entry.o uncompress.o
+pbl-y += nmon_entry.o
 pbl-$(CONFIG_BOARD_GENERIC_DT) += board-dt-2nd.o
diff --git a/arch/riscv/boot/nmon_entry.S b/arch/riscv/boot/nmon_entry.S
new file mode 100644
index 0000000000..ae017d2a1c
--- /dev/null
+++ b/arch/riscv/boot/nmon_entry.S
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/linkage.h>
+#include <asm/sections.h>
+
+#include "asm/debug_ll.h"
+#include "asm/riscv_nmon.h"
+
+.section .text_bare_init
+
+ENTRY(__barebox_nmon_entry)
+	riscv_nmon
+	ret
+ENDPROC(__barebox_nmon_entry)
diff --git a/arch/riscv/include/asm/riscv_nmon.h b/arch/riscv/include/asm/riscv_nmon.h
index caf213cdd8..8a44e216d7 100644
--- a/arch/riscv/include/asm/riscv_nmon.h
+++ b/arch/riscv/include/asm/riscv_nmon.h
@@ -16,13 +16,26 @@
 #ifndef __ASM_RISCV_NMON_H
 #define __ASM_RISCV_NMON_H
 
+#include <linux/kconfig.h>
+
 #define CODE_ESC	0x1b
 
+#ifndef __ASSEMBLY__
+
+extern void __barebox_nmon_entry(void);
+
+static inline void barebox_nmon_entry(void)
+{
+	if (IS_ENABLED(CONFIG_NMON))
+		__barebox_nmon_entry();
+}
+
+#else
+
 .macro nmon_outs msg
 
-	la	a1, \msg
-
-	jal	_nmon_outs
+	lla	a1, \msg
+	jal	a2, _nmon_outs
 
 .endm
 
@@ -73,7 +86,7 @@ nmon_main:
 	li	a0, 'q'
 	bne	s0, a0, 3f
 
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
 	j	nmon_exit
 
@@ -90,12 +103,12 @@ nmon_main:
 	j	nmon_main_help
 
 nmon_cmd_d:
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
 	li	a0, ' '
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
-	jal	_nmon_gethexw
+	jal	a2, _nmon_gethexw
 
 	nmon_outs	msg_nl
 
@@ -105,28 +118,28 @@ nmon_cmd_d:
 	j	nmon_main
 
 nmon_cmd_w:
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
 	li	a0, ' '
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
-	jal	_nmon_gethexw
+	jal	a2, _nmon_gethexw
 	move	s2, s0
 
 	li	a0, ' '
-	jal	_nmon_outc_a0
-	jal	_nmon_gethexw
+	jal	a2, _nmon_outc_a0
+	jal	a2, _nmon_gethexw
 
 	sw	s0, 0(s2)
 	j	nmon_main
 
 nmon_cmd_g:
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
 	li	a0, ' '
-	jal	_nmon_outc_a0
+	jal	a2, _nmon_outc_a0
 
-	jal	_nmon_gethexw
+	jal	a2, _nmon_gethexw
 	move	s2, s0
 
 	nmon_outs	msg_nl
@@ -136,7 +149,7 @@ nmon_cmd_g:
 
 _nmon_outc_a0:
 	debug_ll_outc_a0
-	jr	ra
+	jr	a2
 
 _nmon_outs:
 
@@ -202,7 +215,7 @@ _get_hex_digit:
 	move	s0, t2
 
 _nmon_jr_ra_exit:
-	jr	ra
+	jr	a2
 
 msg_prompt:
 	.asciz "\r\nnmon> "
@@ -231,4 +244,6 @@ nmon_exit:
 
 .endm
 
+#endif /* __ASSEMBLY__ */
+
 #endif /* __ASM_RISCV_NMON_H */
-- 
2.31.1