ramips: make the early_printk code detect which uart is used

only tested on mt7628

Signed-off-by: John Crispin <blogic@openwrt.org>

SVN-Revision: 46950

target/linux/ramips/patches-3.18/0015-MIPS-ralink-cleanup-early_printk.patch

@@ -13,7 +13,7 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 
 --- a/arch/mips/ralink/early_printk.c
 +++ b/arch/mips/ralink/early_printk.c
-@@ -12,21 +12,24 @@
+@@ -12,21 +12,26 @@
  #include <asm/addrspace.h>
  
  #ifdef CONFIG_SOC_RT288X
@@ -40,15 +40,17 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 +#define MT7628_CHIP_NAME1	0x20203832
 +
 +#define UART_REG_TX		0x04
++#define UART_REG_LCR		0x0c
 +#define UART_REG_LSR		0x14
 +#define UART_REG_LSR_RT2880	0x1c
  
  static __iomem void *uart_membase = (__iomem void *) KSEG1ADDR(EARLY_UART_BASE);
 +static __iomem void *chipid_membase = (__iomem void *) KSEG1ADDR(CHIPID_BASE);
++static int init_complete;
  
  static inline void uart_w32(u32 val, unsigned reg)
  {
-@@ -38,11 +41,23 @@ static inline u32 uart_r32(unsigned reg)
+@@ -38,11 +43,46 @@
  	return __raw_readl(uart_membase + reg);
  }
  
@@ -57,6 +59,24 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 +	return IS_ENABLED(CONFIG_SOC_MT7620) &&
 +		(__raw_readl(chipid_membase) == MT7628_CHIP_NAME1);
 +}
++
++static inline void find_uart_base(void)
++{
++	int i;
++
++	if (!soc_is_mt7628())
++		return;
++
++	for (i = 0; i < 3; i++) {
++		u32 reg = uart_r32(UART_REG_LCR + (0x100 * i));
++
++		if (!reg)
++			continue;
++
++		uart_membase = (__iomem void *) KSEG1ADDR(EARLY_UART_BASE + (0x100 * i));
++		break;
++	}
++}
 +
  void prom_putchar(unsigned char ch)
  {
@@ -65,6 +85,11 @@ Signed-off-by: John Crispin <blogic@openwrt.org>
 -	uart_w32(ch, UART_REG_TX);
 -	while ((uart_r32(UART_REG_LSR) & UART_LSR_THRE) == 0)
 -		;
++	if (!init_complete) {
++		find_uart_base();
++		init_complete = 1;
++	}
++
 +	if (IS_ENABLED(CONFIG_SOC_MT7621) || soc_is_mt7628()) {
 +		uart_w32(ch, UART_TX);
 +		while ((uart_r32(UART_REG_LSR) & UART_LSR_THRE) == 0)