[ARM] pxa: refactor uncompress.h for non-PXA uarts

The original patch came from Marc Zyngier where support of 8250-compatible
UART is required to show the uncompress information. Modified a little bit
here, including changes below:

1. #include <mach/regs-uart.h> is actually not necessary
2. introduced uart_{read,write}() for different base and shift
3. introduced uart_is_enabled() and assumed enabled always for
   non-PXA uarts

Signed-off-by: Eric Miao <eric.y.miao@gmail.com>
Acked-by: Marc Zyngier <maz@misterjones.org>

arch/arm/mach-pxa/include/mach/uncompress.h

@@ -10,20 +10,41 @@
  */
 
 #include <linux/serial_reg.h>
-#include <mach/regs-uart.h>
 #include <asm/mach-types.h>
 
-#define __REG(x)       ((volatile unsigned long *)x)
+#define FFUART_BASE	(0x40100000)
+#define BTUART_BASE	(0x40200000)
+#define STUART_BASE	(0x40700000)
 
-static volatile unsigned long *UART = FFUART;
+static unsigned long uart_base = FFUART_BASE;
+static unsigned int uart_shift = 2;
+static unsigned int uart_is_pxa = 1;
+
+static inline unsigned char uart_read(int offset)
+{
+	return *(volatile unsigned char *)(uart_base + (offset << uart_shift));
+}
+
+static inline void uart_write(unsigned char val, int offset)
+{
+	*(volatile unsigned char *)(uart_base + (offset << uart_shift)) = val;
+}
+
+static inline int uart_is_enabled(void)
+{
+	/* assume enabled by default for non-PXA uarts */
+	return uart_is_pxa ? uart_read(UART_IER) & UART_IER_UUE : 1;
+}
 
 static inline void putc(char c)
 {
-	if (!(UART[UART_IER] & IER_UUE))
+	if (!uart_is_enabled())
 		return;
-	while (!(UART[UART_LSR] & LSR_TDRQ))
+
+	while (!(uart_read(UART_LSR) & UART_LSR_THRE))
 		barrier();
-	UART[UART_TX] = c;
+
+	uart_write(c, UART_TX);
 }
 
 /*
@@ -38,7 +59,7 @@ static inline void arch_decomp_setup(void)
 	if (machine_is_littleton() || machine_is_intelmote2()
 	    || machine_is_csb726() || machine_is_stargate2()
 	    || machine_is_cm_x300() || machine_is_balloon3())
-		UART = STUART;
+		uart_base = STUART_BASE;
 }
 
 /*