[PATCH V2 2/2] xen: arm: implement early prink for 8250 uart

[Bamvor Jian Zhang <bjzhang@suse.com>]

implement early printk for 8250 uart which is used by lots of arm SOC, such as
Allwinner A31(sun6i) and OMAP5432.

Signed-off-by: Bamvor Jian Zhang <bjzhang@suse.com>
---
 docs/misc/arm/early-printk.txt    |  1 +
 xen/arch/arm/Rules.mk             |  5 ++++
 xen/arch/arm/arm32/debug-8250.inc | 48 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+)
 create mode 100644 xen/arch/arm/arm32/debug-8250.inc

diff --git a/docs/misc/arm/early-printk.txt b/docs/misc/arm/early-printk.txt
index fbc3208..eaa66a1 100644
--- a/docs/misc/arm/early-printk.txt
+++ b/docs/misc/arm/early-printk.txt
@@ -13,6 +13,7 @@ where mach is the name of the machine:
   - exynos5250: printk with the second UART
   - midway: printk with the pl011 on Calxeda Midway processors
   - fastmodel: printk on ARM Fastmodel software emulators
+  - sun6i: printk with 8250 on Allwinner A31 processors
 
 The base address and baud rate is hardcoded in xen/arch/arm/Rules.mk,
 see there when adding support for new machines.
diff --git a/xen/arch/arm/Rules.mk b/xen/arch/arm/Rules.mk
index 422ed04..51e823d 100644
--- a/xen/arch/arm/Rules.mk
+++ b/xen/arch/arm/Rules.mk
@@ -64,6 +64,11 @@ EARLY_PRINTK_INC := pl011
 EARLY_PRINTK_BAUD := 115200
 EARLY_UART_BASE_ADDRESS := 0xfff36000
 endif
+ifeq ($(CONFIG_EARLY_PRINTK), sun6i)
+# uart configured at 115200 by bootloader
+EARLY_PRINTK_INC := 8250
+EARLY_UART_BASE_ADDRESS := 0x01c28000
+endif
 
 ifneq ($(EARLY_PRINTK_INC),)
 EARLY_PRINTK := y
diff --git a/xen/arch/arm/arm32/debug-8250.inc b/xen/arch/arm/arm32/debug-8250.inc
new file mode 100644
index 0000000..c11357d
--- /dev/null
+++ b/xen/arch/arm/arm32/debug-8250.inc
@@ -0,0 +1,48 @@
+/*
+ * xen/arch/arm/arm32/debug-8250.inc
+ *
+ * 8250 specific debug code
+ *
+ * Bamvor Jian Zhang <bjzhang@suse.com>
+ * Copyright (c) 2013 SUSE
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ */
+
+
+#define UART_TX           (0x00<<2)    /* Out: Transmit buffer */
+#define UART_LSR          (0x05<<2)    /* In:  Line Status Register */
+
+#define UART_LSR_THRE     0x20         /* Xmit holding register empty */
+
+/* 8250 UART wait UART to be ready to transmit
+ * rb: register which contains the UART base address
+ * rc: scratch register */
+.macro early_uart_ready rb, rc
+1:
+        ldr   \rc, [\rb, #UART_LSR]    /* <- UART_LSR (Line Status Register) */
+        tst   \rc, #UART_LSR_THRE      /* Check BUSY bit */
+        beq   1b                       /* Wait for the UART to be ready */
+.endm
+
+/* 8250 UART transmit character
+ * rb: register which contains the UART base address
+ * rt: register which contains the character to transmit */
+.macro early_uart_transmit rb, rt
+        str   \rt, [\rb, #UART_TX]     /* -> UART_TX */
+.endm
+
+/*
+ * Local variables:
+ * mode: ASM
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
1.8.1.4