ARM: OMAP4: MMC: increase delay for pbias

4 micro seconds is not enough for PBIAS if MMC regulator is
enabled from MMC regulator OFF.
Increase the delay for PBIAS to stabilize.
Wait for PBIAS and timeout if not.

Resolves MMC/SD failure on OMAP4
"Pbias Voltage is not same as LDO"

Signed-off-by: Balaji T K <balajitk@ti.com>
Acked-by:  Kishore Kadiyala <kishore.kadiyala@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/hsmmc.c

@@ -145,6 +145,7 @@ static void omap4_hsmmc1_after_set_reg(struct device *dev, int slot,
 				 int power_on, int vdd)
 {
 	u32 reg;
+	unsigned long timeout;
 
 	if (power_on) {
 		reg = omap4_ctrl_pad_readl(control_pbias_offset);
@@ -157,9 +158,15 @@ static void omap4_hsmmc1_after_set_reg(struct device *dev, int slot,
 			OMAP4_MMC1_PWRDNZ_MASK |
 			OMAP4_USBC1_ICUSB_PWRDNZ_MASK);
 		omap4_ctrl_pad_writel(reg, control_pbias_offset);
-		/* 4 microsec delay for comparator to generate an error*/
-		udelay(4);
-		reg = omap4_ctrl_pad_readl(control_pbias_offset);
+
+		timeout = jiffies + msecs_to_jiffies(5);
+		do {
+			reg = omap4_ctrl_pad_readl(control_pbias_offset);
+			if (!(reg & OMAP4_MMC1_PBIASLITE_VMODE_ERROR_MASK))
+				break;
+			usleep_range(100, 200);
+		} while (!time_after(jiffies, timeout));
+
 		if (reg & OMAP4_MMC1_PBIASLITE_VMODE_ERROR_MASK) {
 			pr_err("Pbias Voltage is not same as LDO\n");
 			/* Caution : On VMODE_ERROR Power Down MMC IO */