memory: omap-gpmc: Add GPMC-NAND ops to get writebufferempty status

This is needed by OMAP NAND driver to poll the empty status
of the writebuffer.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>

drivers/memory/omap-gpmc.c

@@ -81,6 +81,8 @@
 
 #define GPMC_CONFIG_LIMITEDADDRESS		BIT(1)
 
+#define GPMC_STATUS_EMPTYWRITEBUFFERSTATUS	BIT(0)
+
 #define	GPMC_CONFIG2_CSEXTRADELAY		BIT(7)
 #define	GPMC_CONFIG3_ADVEXTRADELAY		BIT(7)
 #define	GPMC_CONFIG4_OEEXTRADELAY		BIT(7)
@@ -1118,7 +1120,17 @@ void gpmc_update_nand_reg(struct gpmc_nand_regs *reg, int cs)
 	}
 }
 
-static struct gpmc_nand_ops nand_ops;
+static bool gpmc_nand_writebuffer_empty(void)
+{
+	if (gpmc_read_reg(GPMC_STATUS) & GPMC_STATUS_EMPTYWRITEBUFFERSTATUS)
+		return true;
+
+	return false;
+}
+
+static struct gpmc_nand_ops nand_ops = {
+	.nand_writebuffer_empty = gpmc_nand_writebuffer_empty,
+};
 
 /**
  * gpmc_omap_get_nand_ops - Get the GPMC NAND interface