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spring: Hard-limit current draw from Toad

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The Toad cable is browning out from time to time. Let's limit its
current in aggressive mode.

Also fix a bug in hard current limit calculation.

BUG=None
TEST=Plug-in Toad cable and see PWM duty cycle starts higher.
BRANCH=Spring

Change-Id: I06d64418989aa32a99545986fe841914f054acde
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/59161
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
This commit is contained in:
Vic Yang
2013-06-19 10:46:43 +08:00
committed by ChromeBot
parent 89ee180156
commit c5d978baac
1 changed files with 9 additions and 1 deletions
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10
common/extpower_usb.c
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@@ -278,8 +278,14 @@ static int apple_charger_current(void)
static int hard_current_limit(int limit)
{
/*
* In aggressive mode, the PWM duty cycle goes lower than the nominal
* cycle for PWM_CTRL_OC_MARGIN. Therefore, increase duty cycle by
* PWM_CTRL_OC_MARGIN avoids going over the hard limit.
* (Note that lower PWM cycle translates to higher current)
*/
if (current_limit_mode == LIMIT_AGGRESSIVE)
return limit - PWM_CTRL_OC_MARGIN;
return MIN(limit + PWM_CTRL_OC_MARGIN, 100);
else
return limit;
}
@@ -524,6 +530,8 @@ static void usb_update_ilim(int dev_type)
current_limit = hard_current_limit(I_LIMIT_1500MA);
else if (dev_type & TSU6721_TYPE_JIG_UART_ON)
current_limit = hard_current_limit(I_LIMIT_2000MA);
else if (dev_type & TOAD_DEVICE_TYPE)
current_limit = hard_current_limit(I_LIMIT_500MA);
pwm_nominal_duty_cycle(current_limit);
} else {