ARM: uniphier: support Debug UART

For ARM32 architecture, CONFIG_DEBUG_LL is available for early
low-level debugging (and actually UniPhier 32bit SoCs use it), but
ARM64 architecture does not support it.  Instead, CONFIG_DEBUG_UART
is available as an architecture-independent debug facility.

This commit supports it on all the UniPhier SoCs (including the new
ARMv8 SoCs), which is very useful for new SoC bringups.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/arch/arm/mach-uniphier/debug-uart/debug-uart-ld20.c b/arch/arm/mach-uniphier/debug-uart/debug-uart-ld20.c
new file mode 100644
index 0000000000..2dc2bf8547
--- /dev/null
+++ b/arch/arm/mach-uniphier/debug-uart/debug-uart-ld20.c
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2016 Masahiro Yamada <yamada.masahiro@socionext.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <config.h>
+#include <linux/kernel.h>
+#include <linux/io.h>
+
+#include "../sc64-regs.h"
+#include "../sg-regs.h"
+#include "debug-uart.h"
+
+#define UNIPHIER_LD20_UART_CLK		58820000
+
+unsigned int uniphier_ld20_debug_uart_init(void)
+{
+	u32 tmp;
+
+	sg_set_iectrl(54);		/* TXD0 */
+	sg_set_iectrl(58);		/* TXD1 */
+	sg_set_iectrl(90);		/* TXD2 */
+	sg_set_iectrl(94);		/* TXD3 */
+	sg_set_pinsel(54, 0, 8, 4);	/* TXD0 -> TXD0 */
+	sg_set_pinsel(58, 1, 8, 4);	/* SPITXD1 -> TXD1 */
+	sg_set_pinsel(90, 1, 8, 4);	/* PC0WE -> TXD2 */
+	sg_set_pinsel(94, 1, 8, 4);	/* PCD00 -> TXD3 */
+
+	tmp = readl(SC_CLKCTRL4);
+	tmp |= SC_CLKCTRL4_PERI;
+	writel(tmp, SC_CLKCTRL4);
+
+	return DIV_ROUND_CLOSEST(UNIPHIER_LD20_UART_CLK, 16 * CONFIG_BAUDRATE);
+}