commit d1bdef008a33e4e9583606feb8747a4d0d249ef1
author huang lin <hl@rock-chips.com> Fri Oct 31 16:40:42 2014 +0800
committer Patrick Georgi <pgeorgi@google.com> Fri Apr 10 11:58:18 2015 +0200
tree 8e63164cda0d74dff50b1e16fe18ad9080eff66c
parent c06a962271053d1fbb280e28e1cd5788132d942c

rk3288: slowly raise to max cpu voltage to prevent overshoot

slowly raise to max cpu voltage to prevent overshoot,
and in our experience,when cpu run in 1.8GHz,the
vdd_cpu must up to 1.4V

BUG=chrome-os-partner:32716, chrome-os-partner:31896
TEST=Boot on veyron_pinky rev2,check the rk808 buck1 voltage 1400mv
     and measure the overshoot is 1440mv

Change-Id: I759840bd8cf57a5589bf1862d04803f80f804164
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 567f616ff091883ed3275b407859c9399db981b2
Original-Change-Id: I9bb739b49ae4b4f7a60133fa38b0fe51b95c0d78
Original-Signed-off-by: huang lin <hl@rock-chips.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/226753
Original-Reviewed-by: Doug Anderson <dianders@chromium.org>
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/9408
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/mainboard/google/veyron_pinky/bootblock.c

diff --git a/src/mainboard/google/veyron_pinky/bootblock.c b/src/mainboard/google/veyron_pinky/bootblock.c
index b34199d..99719c4 100644
--- a/src/mainboard/google/veyron_pinky/bootblock.c
+++ b/src/mainboard/google/veyron_pinky/bootblock.c
@@ -27,16 +27,25 @@
 #include <soc/rk808.h>
 #include <soc/spi.h>
 #include <vendorcode/google/chromeos/chromeos.h>
+#include <delay.h>
 
 #include "board.h"
 
 void bootblock_mainboard_init(void)
 {
-	/* cpu frequency will up to 1.8GHz, so the buck1 must up to 1.3v */
+	/* cpu frequency will up to 1.8GHz,
+	 * in our experience the buck1
+	 * must up to 1.4v
+	 */
 	setbits_le32(&rk3288_pmu->iomux_i2c0scl, IOMUX_I2C0SCL);
 	setbits_le32(&rk3288_pmu->iomux_i2c0sda, IOMUX_I2C0SDA);
 	i2c_init(PMIC_BUS, 400*KHz);
-	rk808_configure_buck(PMIC_BUS, 1, 1300);
+
+	/* Slowly raise to max CPU voltage to prevent overshoot */
+	rk808_configure_buck(PMIC_BUS, 1, 1200);
+	udelay(175);/* Must wait for voltage to stabilize,2mV/us */
+	rk808_configure_buck(PMIC_BUS, 1, 1400);
+	udelay(100);/* Must wait for voltage to stabilize,2mV/us */
 	rkclk_configure_cpu();
 
 	/* i2c1 for tpm */

src/soc/rockchip/rk3288/rk808.c

diff --git a/src/soc/rockchip/rk3288/rk808.c b/src/soc/rockchip/rk3288/rk808.c
index aa39b8d..fea64e5 100644
--- a/src/soc/rockchip/rk3288/rk808.c
+++ b/src/soc/rockchip/rk3288/rk808.c
@@ -98,5 +98,4 @@
 	}
 	rk808_clrsetbits(bus, buck_reg, 0x3f, vsel);
 	rk808_clrsetbits(bus, DCDC_EN, 0, 1 << (buck - 1));
-	udelay(225);/* Must wait for voltage to stabilize */
 }