[RFC v4 03/10] RISC-V: add low-level debug macros for ns16550

[Antony Pavlov <antonynpavlov@gmail.com>]

This patch adds macros for ns16550 port initialisation
and single char output. The macros can be used in
MIPS asm pbl code.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
---
 arch/riscv/include/asm/debug_ll_ns16550.h | 186 ++++++++++++++++++++++++++++++
 1 file changed, 186 insertions(+)

diff --git a/arch/riscv/include/asm/debug_ll_ns16550.h b/arch/riscv/include/asm/debug_ll_ns16550.h
new file mode 100644
index 000000000..6929453b1
--- /dev/null
+++ b/arch/riscv/include/asm/debug_ll_ns16550.h
@@ -0,0 +1,186 @@
+/*
+ * Copyright (C) 2016, 2017 Antony Pavlov <antonynpavlov@gmail.com>
+ *
+ * This file is part of barebox.
+ * See file CREDITS for list of people who contributed to this project.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+/** @file
+ *  This file contains declaration for early output support
+ */
+#ifndef __INCLUDE_RISCV_ASM_DEBUG_LL_NS16550_H__
+#define __INCLUDE_RISCV_ASM_DEBUG_LL_NS16550_H__
+
+#include <linux/kconfig.h>
+
+#ifdef CONFIG_DEBUG_LL
+
+#ifndef DEBUG_LL_UART_ADDR
+#error DEBUG_LL_UART_ADDR is undefined!
+#endif
+
+#ifndef DEBUG_LL_UART_SHIFT
+#error DEBUG_LL_UART_SHIFT is undefined!
+#endif
+
+#ifndef DEBUG_LL_UART_DIVISOR
+#error DEBUG_LL_UART_DIVISOR is undefined!
+#endif
+
+#endif /* CONFIG_DEBUG_LL */
+
+#define UART_THR	(0x0 << DEBUG_LL_UART_SHIFT)
+#define UART_RBR	(0x0 << DEBUG_LL_UART_SHIFT)
+#define UART_DLL	(0x0 << DEBUG_LL_UART_SHIFT)
+#define UART_DLM	(0x1 << DEBUG_LL_UART_SHIFT)
+#define UART_LCR	(0x3 << DEBUG_LL_UART_SHIFT)
+#define UART_LSR	(0x5 << DEBUG_LL_UART_SHIFT)
+
+#define UART_LCR_W	0x07	/* Set UART to 8,N,2 & DLAB = 0 */
+#define UART_LCR_DLAB	0x87	/* Set UART to 8,N,2 & DLAB = 1 */
+
+#define UART_LSR_DR	0x01    /* UART received data present */
+#define UART_LSR_THRE	0x20	/* Xmit holding register empty */
+
+#if defined(DEBUG_LL_UART_IOSIZE32)
+#define UART_REG_L	lw
+#define UART_REG_S	sw
+#elif defined(DEBUG_LL_UART_IOSIZE8)
+#define UART_REG_L	lbu
+#define UART_REG_S	sb
+#else
+#error "Please define DEBUG_LL_UART_IOSIZE{8,32}"
+#endif
+
+#ifndef __ASSEMBLY__
+/*
+ * C macros
+ */
+
+#include <asm/io.h>
+
+static inline void PUTC_LL(char ch)
+{
+#ifdef CONFIG_DEBUG_LL
+	while (!(__raw_readl((u8 *)DEBUG_LL_UART_ADDR + UART_LSR) & UART_LSR_THRE))
+		;
+	__raw_writel(ch, (u8 *)DEBUG_LL_UART_ADDR + UART_THR);
+#endif /* CONFIG_DEBUG_LL */
+}
+
+static inline void debug_ll_ns16550_init(void)
+{
+#ifdef CONFIG_DEBUG_LL
+	__raw_writel(UART_LCR_DLAB, (u8 *)DEBUG_LL_UART_ADDR + UART_LCR);
+	__raw_writel(DEBUG_LL_UART_DIVISOR & 0xff, (u8 *)DEBUG_LL_UART_ADDR + UART_DLL);
+	__raw_writel((DEBUG_LL_UART_DIVISOR >> 8) & 0xff, (u8 *)DEBUG_LL_UART_ADDR + UART_DLM);
+	__raw_writel(UART_LCR_W, (u8 *)DEBUG_LL_UART_ADDR + UART_LCR);
+#endif /* CONFIG_DEBUG_LL */
+}
+#else /* __ASSEMBLY__ */
+/*
+ * Macros for use in assembly language code
+ */
+
+.macro	debug_ll_ns16550_init
+#ifdef CONFIG_DEBUG_LL
+	li	t0, DEBUG_LL_UART_ADDR
+
+	li	t1, UART_LCR_DLAB		/* DLAB on */
+	UART_REG_S	t1, UART_LCR(t0)		/* Write it out */
+
+	li	t1, DEBUG_LL_UART_DIVISOR
+	UART_REG_S	t1, UART_DLL(t0)		/* write low order byte */
+	srl	t1, t1, 8
+	UART_REG_S	t1, UART_DLM(t0)		/* write high order byte */
+
+	li	t1, UART_LCR_W			/* DLAB off */
+	UART_REG_S	t1, UART_LCR(t0)		/* Write it out */
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * output a character in a0
+ */
+.macro	debug_ll_outc_a0
+#ifdef CONFIG_DEBUG_LL
+
+	li	t0, DEBUG_LL_UART_ADDR
+
+201:
+	UART_REG_L	t1, UART_LSR(t0)	/* get line status */
+	andi	t1, t1, UART_LSR_THRE	/* check for transmitter empty */
+	beqz	t1, 201b			/* try again */
+
+	UART_REG_S	a0, UART_THR(t0)	/* write the character */
+
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * output a character
+ */
+.macro	debug_ll_outc chr
+#ifdef CONFIG_DEBUG_LL
+	li	a0, \chr
+	debug_ll_outc_a0
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * output CR + NL
+ */
+.macro	debug_ll_ns16550_outnl
+#ifdef CONFIG_DEBUG_LL
+	debug_ll_outc '\r'
+	debug_ll_outc '\n'
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * check character in input buffer
+ * return value:
+ *  v0 = 0   no character in input buffer
+ *  v0 != 0  character in input buffer
+ */
+.macro	debug_ll_tstc
+#ifdef CONFIG_DEBUG_LL
+	li      t0, DEBUG_LL_UART_ADDR
+
+	/* get line status and check for data present */
+	UART_REG_L	s0, UART_LSR(t0)
+	andi	s0, s0, UART_LSR_DR
+
+#endif /* CONFIG_DEBUG_LL */
+.endm
+
+/*
+ * get character to v0
+ */
+.macro	debug_ll_getc
+#ifdef CONFIG_DEBUG_LL
+
+204:
+	debug_ll_tstc
+
+	/* try again */
+	beqz	s0, 204b
+
+	/* read a character */
+	UART_REG_L	s0, UART_RBR(t0)
+
+#endif /* CONFIG_DEBUG_LL */
+.endm
+#endif /* __ASSEMBLY__ */
+
+#endif /* __INCLUDE_RISCV_ASM_DEBUG_LL_NS16550_H__ */
-- 
2.14.1


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