spl: nand: sunxi: ensure enough time has passed after changing the column

When changing the column, the ONFI specification states that a minimum
time of tCCS (Change Column Setup time) must elapse between the last
address cycle is asserted on the bus and the first data cycle is
clocked. An usual value for average NANDs is 500 nanoseconds. Round it
up to 1 microsecond to be safe.
Signed-off-by: NMiquel Raynal <miquel.raynal@bootlin.com>
Acked-by: NBoris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: NMaxime Ripard <maxime.ripard@bootlin.com>

drivers/mtd/nand/sunxi_nand_spl.c

@@ -243,15 +243,24 @@ static int nand_load_page(const struct nfc_config *conf, u32 offs)
 
 static int nand_reset_column(void)
 {
+	int ret;
+
 	writel((NFC_CMD_RNDOUTSTART << NFC_RANDOM_READ_CMD1_OFFSET) |
 	       (NFC_CMD_RNDOUT << NFC_RANDOM_READ_CMD0_OFFSET) |
 	       (NFC_CMD_RNDOUTSTART << NFC_READ_CMD_OFFSET),
 	       SUNXI_NFC_BASE + NFC_RCMD_SET);
 	writel(0, SUNXI_NFC_BASE + NFC_ADDR_LOW);
 
-	return nand_exec_cmd(NFC_SEND_CMD1 | NFC_SEND_CMD2 | NFC_RAW_CMD |
-			     (1 << NFC_ADDR_NUM_OFFSET) | NFC_SEND_ADDR |
-			     NFC_CMD_RNDOUT);
+	ret = nand_exec_cmd(NFC_SEND_CMD1 | NFC_SEND_CMD2 | NFC_RAW_CMD |
+			    (1 << NFC_ADDR_NUM_OFFSET) | NFC_SEND_ADDR |
+			    NFC_CMD_RNDOUT);
+	if (ret)
+		return ret;
+
+	/* Ensure tCCS has passed before reading data */
+	udelay(1);
+
+	return 0;
 }
 
 static int nand_read_page(const struct nfc_config *conf, u32 offs,