arm: rmobile: kzm9g: Adjust SDRAM setting

After stress test, I found some of kzm9g board occures memory failure.
This patch adust SDRAM setting.
- Enlarge drivability on both SDRAM controller and SDRAM itself
- Raise core voltage

Signed-off-by: Tetsuyuki Kobayashi <koba@kmckk.co.jp>
Acked-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>

board/kmc/kzm9g/kzm9g.c

@@ -84,7 +84,7 @@ static void sbsc_init(struct sh73a0_sbsc *sbsc)
 	writel(0x0017040a, &sbsc->sdwcr01);
 	writel(0x31020707, &sbsc->sdwcr10);
 	writel(0x0017040a, &sbsc->sdwcr11);
-	writel(0x05555555, &sbsc->sddrvcr0);
+	writel(0x055557ff, &sbsc->sddrvcr0); /* Enlarge drivability of LPDQS0-3, LPCLK */
 	writel(0x30000000, &sbsc->sdwcr2);
 
 	writel(readl(&sbsc->sdpcr) | 0x80, &sbsc->sdpcr);
@@ -112,7 +112,7 @@ static void sbsc_init(struct sh73a0_sbsc *sbsc)
 		writel(0x0, SDMRA1A);
 		writel(0x00000402, &sbsc->sdmracr0);
 		writel(0x0, SDMRA1A);
-		writel(0x00000403, &sbsc->sdmracr0);
+		writel(0x00000203, &sbsc->sdmracr0); /* MR3 register DS=2 */
 		writel(0x0, SDMRA1A);
 		writel(0x0, SDMRA2A);
 	} else {
@@ -120,7 +120,7 @@ static void sbsc_init(struct sh73a0_sbsc *sbsc)
 		writel(0x0, SDMRA1B);
 		writel(0x00000402, &sbsc->sdmracr0);
 		writel(0x0, SDMRA1B);
-		writel(0x00000403, &sbsc->sdmracr0);
+		writel(0x00000203, &sbsc->sdmracr0); /* MR3 register DS=2 */
 		writel(0x0, SDMRA1B);
 		writel(0x0, SDMRA2B);
 	}
@@ -301,8 +301,19 @@ int board_early_init_f(void)
 	return 0;
 }
 
+void adjust_core_voltage(void)
+{
+	u8 data;
+
+	i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
+	data = 0x35;
+	i2c_set_bus_num(0);
+	i2c_write(0x40, 3, 1, &data, 1);
+}
+
 int board_init(void)
 {
+	adjust_core_voltage();
 	sh73a0_pinmux_init();
 
     /* SCIFA 4 */