riscv: sifive: fu540: Setup ethaddr env variable using OTP

This patch extends SiFive FU540 board support to setup ethaddr
env variable based on board serialnum read from OTP.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

board/sifive/fu540/fu540.c

@@ -8,6 +8,128 @@
 
 #include <common.h>
 #include <dm.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+
+#ifdef CONFIG_MISC_INIT_R
+
+#define FU540_OTP_BASE_ADDR			0x10070000
+
+struct fu540_otp_regs {
+	u32 pa;     /* Address input */
+	u32 paio;   /* Program address input */
+	u32 pas;    /* Program redundancy cell selection input */
+	u32 pce;    /* OTP Macro enable input */
+	u32 pclk;   /* Clock input */
+	u32 pdin;   /* Write data input */
+	u32 pdout;  /* Read data output */
+	u32 pdstb;  /* Deep standby mode enable input (active low) */
+	u32 pprog;  /* Program mode enable input */
+	u32 ptc;    /* Test column enable input */
+	u32 ptm;    /* Test mode enable input */
+	u32 ptm_rep;/* Repair function test mode enable input */
+	u32 ptr;    /* Test row enable input */
+	u32 ptrim;  /* Repair function enable input */
+	u32 pwe;    /* Write enable input (defines program cycle) */
+} __packed;
+
+#define BYTES_PER_FUSE				4
+#define NUM_FUSES				0x1000
+
+static int fu540_otp_read(int offset, void *buf, int size)
+{
+	struct fu540_otp_regs *regs = (void __iomem *)FU540_OTP_BASE_ADDR;
+	unsigned int i;
+	int fuseidx = offset / BYTES_PER_FUSE;
+	int fusecount = size / BYTES_PER_FUSE;
+	u32 fusebuf[fusecount];
+
+	/* check bounds */
+	if (offset < 0 || size < 0)
+		return -EINVAL;
+	if (fuseidx >= NUM_FUSES)
+		return -EINVAL;
+	if ((fuseidx + fusecount) > NUM_FUSES)
+		return -EINVAL;
+
+	/* init OTP */
+	writel(0x01, &regs->pdstb); /* wake up from stand-by */
+	writel(0x01, &regs->ptrim); /* enable repair function */
+	writel(0x01, &regs->pce);   /* enable input */
+
+	/* read all requested fuses */
+	for (i = 0; i < fusecount; i++, fuseidx++) {
+		writel(fuseidx, &regs->pa);
+
+		/* cycle clock to read */
+		writel(0x01, &regs->pclk);
+		mdelay(1);
+		writel(0x00, &regs->pclk);
+		mdelay(1);
+
+		/* read the value */
+		fusebuf[i] = readl(&regs->pdout);
+	}
+
+	/* shut down */
+	writel(0, &regs->pce);
+	writel(0, &regs->ptrim);
+	writel(0, &regs->pdstb);
+
+	/* copy out */
+	memcpy(buf, fusebuf, size);
+
+	return 0;
+}
+
+static u32 fu540_read_serialnum(void)
+{
+	int ret;
+	u32 serial[2] = {0};
+
+	for (int i = 0xfe * 4; i > 0; i -= 8) {
+		ret = fu540_otp_read(i, serial, sizeof(serial));
+		if (ret) {
+			printf("%s: error reading from OTP\n", __func__);
+			break;
+		}
+		if (serial[0] == ~serial[1])
+			return serial[0];
+	}
+
+	return 0;
+}
+
+static void fu540_setup_macaddr(u32 serialnum)
+{
+	/* Default MAC address */
+	unsigned char mac[6] = { 0x70, 0xb3, 0xd5, 0x92, 0xf0, 0x00 };
+
+	/*
+	 * We derive our board MAC address by ORing last three bytes
+	 * of board serial number to above default MAC address.
+	 *
+	 * This logic of deriving board MAC address is taken from
+	 * SiFive FSBL and is kept unchanged.
+	 */
+	mac[5] |= (serialnum >>  0) & 0xff;
+	mac[4] |= (serialnum >>  8) & 0xff;
+	mac[3] |= (serialnum >> 16) & 0xff;
+
+	/* Update environment variable */
+	eth_env_set_enetaddr("ethaddr", mac);
+}
+
+int misc_init_r(void)
+{
+	/* Set ethaddr environment variable if not set */
+	if (!env_get("ethaddr"))
+		fu540_setup_macaddr(fu540_read_serialnum());
+
+	return 0;
+}
+
+#endif
 
 int board_init(void)
 {

configs/sifive_fu540_defconfig

@@ -7,4 +7,5 @@ CONFIG_DISTRO_DEFAULTS=y
 CONFIG_FIT=y
 CONFIG_DISPLAY_CPUINFO=y
 CONFIG_DISPLAY_BOARDINFO=y
+CONFIG_MISC_INIT_R=y
 CONFIG_OF_PRIOR_STAGE=y