Added nand_read.c for start_rvds.s

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@384 bbd45198-f89e-11dd-88c7-29a3b14d5316

libcpu/arm/s3c24x0/nand_read.c

+/* 
+ * nand flash read
+ */
+
+#define NFCONF				(*(volatile unsigned int  *)0x4e000000)
+#define rNFCONT				(*(volatile unsigned int  *)0x4E000004)
+#define NFCMD				(*(volatile unsigned int  *)0x4e000008)
+#define NFADDR				(*(volatile unsigned char *)0x4e00000C)
+#define NFDATA				(*(volatile unsigned char *)0x4e000010)
+#define NFSTAT				(*(volatile unsigned char *)0x4e000020)
+
+#define BUSY				1
+
+#define NAND_SECTOR_SIZE	512
+#define NAND_BLOCK_MASK		(NAND_SECTOR_SIZE - 1)
+
+void wait_idle(void) {
+	int i;
+
+	while (!(NFSTAT & BUSY)) {
+		for(i=0; i<10; i++) {
+			;
+		}
+	}
+}
+
+/* low level nand read function */
+int nand_read_ll(unsigned char *buf, unsigned long start_addr, int size)
+{
+	int i, j;
+
+	/*
+	 * K9F5608UOC asks for 512B per page, and read/write operation must
+	 * do with page. Therefore, first judge whether start_addr and size
+	 * are valid.
+	 */ 
+	if ((start_addr & NAND_BLOCK_MASK) || (size & NAND_BLOCK_MASK)) {
+		return -1;	/* invalid alignment */
+	}
+
+	/* chip Enable */
+	NFCONF &= ~0x800;
+	for (i=0; i<10; i++) {
+		;
+	}
+
+	for (i=start_addr; i < (start_addr + size); i+=NAND_SECTOR_SIZE) {
+		NFCMD = 0;
+
+		/* Write Address */
+		NFADDR = i & 0xff;
+		NFADDR = (i >> 9) & 0xff;
+		NFADDR = (i >> 17) & 0xff;
+		NFADDR = (i >> 25) & 0xff;
+
+		wait_idle();
+
+ 		for(j=0; j < NAND_SECTOR_SIZE; j++) {
+			*buf++ = (NFDATA & 0xff);
+		}
+	}
+
+	/* chip Disable */
+	NFCONF |= 0x800;	/* chip disable */
+
+	return 0;
+}