link: Enable +5VALW at boot and leave it enabled

This works around a problem where disabling +5VALW glitches +3VALW_EC,
which may cause the EC to brown out or hang.

BUG=chrome-os-partner:16600
BRANCH=link
TEST=manual

1. When the system boots, look for this line as the first x86 power state:
  [0.004977 x86 power state 0 = G3, in 0x0001]
2. Boot the system.  Should boot normally.
3. Shut down the system using the power button.
4. After ~10 seconds, you should see that line of output again.
5. At the EC console: 'gpioget enable_5valw' should output:
  1* ENABLE_5VALW

This should ideally be combined with a hardware fix to add 30+ ms of
delay to EC_EN_5V, since when the EC is reset via power+refresh that
tri-states EC_EN_5V, and it takes ~22ms for the EC to boot and start
driving EC_EN_5V again.

Change-Id: Iba4d961d064105faf988a35c2277e9d7406e39e2
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39334
Reviewed-by: Yung-Chieh Lo <yjlou@chromium.org>

2 files changed, 8 insertions, 8 deletions

diff --git a/board/link/board.c b/board/link/board.c
index dae823e3b6..bb72fdccc1 100644
--- a/board/link/board.c
+++ b/board/link/board.c
@@ -76,7 +76,7 @@ const struct gpio_info gpio_list[GPIO_COUNT] = {
 	/* Outputs; all unasserted by default except for reset signals */
 	{"CPU_PROCHOT",         LM4_GPIO_F, (1<<2), GPIO_OUT_LOW, NULL},
 	{"ENABLE_1_5V_DDR",     LM4_GPIO_H, (1<<5), GPIO_OUT_LOW, NULL},
-	{"ENABLE_5VALW",        LM4_GPIO_K, (1<<4), GPIO_OUT_LOW, NULL},
+	{"ENABLE_5VALW",        LM4_GPIO_K, (1<<4), GPIO_OUT_HIGH, NULL},
 	{"ENABLE_BACKLIGHT",    LM4_GPIO_H, (1<<4), GPIO_OUT_LOW, NULL},
 	{"ENABLE_TOUCHPAD",     LM4_GPIO_C, (1<<6), GPIO_OUT_LOW, NULL},
 	{"ENABLE_VCORE",        LM4_GPIO_F, (1<<7), GPIO_OUT_LOW, NULL},
diff --git a/common/x86_power.c b/common/x86_power.c
index 2bbe8e469e..75c2905700 100644
--- a/common/x86_power.c
+++ b/common/x86_power.c
@@ -359,7 +359,6 @@ static void x86_power_init(void)
 			gpio_set_level(GPIO_ENABLE_1_5V_DDR, 0);
 			gpio_set_level(GPIO_PCH_RSMRSTn, 0);
 			gpio_set_level(GPIO_PCH_DPWROK, 0);
-			gpio_set_level(GPIO_ENABLE_5VALW, 0);
 		}
 	}
 
@@ -513,8 +512,6 @@ void x86_power_task(void)
 			break;
 
 		case X86_S5S3:
-			/* Switch on +5V always-on */
-			gpio_set_level(GPIO_ENABLE_5VALW, 1);
 			/* Wait for the always-on rails to be good */
 			wait_in_signals(IN_PGOOD_ALWAYS_ON);
 
@@ -625,14 +622,17 @@ void x86_power_task(void)
 
 			/*
 			 * Put touchscreen and lightbar in reset, so we won't
-			 * leak +3VALW through the reset line.
+			 * leak +3VALW through the reset line to chips powered
+			 * by +5VALW.
+			 *
+			 * (Note that we're no longer powering down +5VALW due
+			 * to crosbug.com/p/16600, but to minimize side effects
+			 * of that change we'll still reset these components in
+			 * S5.)
 			 */
 			gpio_set_level(GPIO_TOUCHSCREEN_RESETn, 0);
 			gpio_set_level(GPIO_LIGHTBAR_RESETn, 0);
 
-			/* Switch off +5V always-on */
-			gpio_set_level(GPIO_ENABLE_5VALW, 0);
-
 			state = X86_S5;
 			break;