From 21ae40404f3ca66fb37dd26e7b67eb109f2453ab Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 30 Jul 2015 10:11:24 +1000 Subject: [PATCH] twl4030_charger: Increase current carefully while watching voltage. The USB Battery Charging spec (BC1.2) suggests a dedicated charging port can deliver from 0.5 to 5.0A at between 4.75 and 5.25 volts. To choose the "correct" current voltage setting requires a trial and error approach: try to draw current and see if the voltage drops too low. Even with a configured Standard Downstream Port, it may not be possible to reliably pull 500mA - depending on cable quality and source quality I have reports of charging failure due to the voltage dropping too low. To address both these concerns, this patch introduce incremental current setting. The current pull from VBUS is increased in steps of 20mA every 100ms until the target is reached or until the measure voltage drops below 4.75V. If the voltage does go too low, the target current is reduced by 20mA and kept there. This applies to currents selected automatically, or to values set via sysfs. So setting a large value will cause the maximum available to be used - up to the limit of 1.7A imposed by the hardware. Signed-off-by: NeilBrown Signed-off-by: Sebastian Reichel --- drivers/power/twl4030_charger.c | 67 ++++++++++++++++++++++++++++++--- 1 file changed, 61 insertions(+), 6 deletions(-) diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c index 68117ad23564..2c537ee11bbe 100644 --- a/drivers/power/twl4030_charger.c +++ b/drivers/power/twl4030_charger.c @@ -119,6 +119,18 @@ struct twl4030_bci { #define CHARGE_AUTO 1 #define CHARGE_LINEAR 2 + /* When setting the USB current we slowly increase the + * requested current until target is reached or the voltage + * drops below 4.75V. In the latter case we step back one + * step. + */ + unsigned int usb_cur_target; + struct delayed_work current_worker; +#define USB_CUR_STEP 20000 /* 20mA at a time */ +#define USB_MIN_VOLT 4750000 /* 4.75V */ +#define USB_CUR_DELAY msecs_to_jiffies(100) +#define USB_MAX_CURRENT 1700000 /* TWL4030 caps at 1.7A */ + unsigned long event; }; @@ -257,6 +269,12 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) } else { cur = bci->usb_cur; bci->ac_is_active = false; + if (cur > bci->usb_cur_target) { + cur = bci->usb_cur_target; + bci->usb_cur = cur; + } + if (cur < bci->usb_cur_target) + schedule_delayed_work(&bci->current_worker, USB_CUR_DELAY); } /* First, check thresholds and see if cgain is needed */ @@ -391,6 +409,41 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) return 0; } +static int twl4030_charger_get_current(void); + +static void twl4030_current_worker(struct work_struct *data) +{ + int v, curr; + int res; + struct twl4030_bci *bci = container_of(data, struct twl4030_bci, + current_worker.work); + + res = twl4030bci_read_adc_val(TWL4030_BCIVBUS); + if (res < 0) + v = 0; + else + /* BCIVBUS uses ADCIN8, 7/1023 V/step */ + v = res * 6843; + curr = twl4030_charger_get_current(); + + dev_dbg(bci->dev, "v=%d cur=%d limit=%d target=%d\n", v, curr, + bci->usb_cur, bci->usb_cur_target); + + if (v < USB_MIN_VOLT) { + /* Back up and stop adjusting. */ + bci->usb_cur -= USB_CUR_STEP; + bci->usb_cur_target = bci->usb_cur; + } else if (bci->usb_cur >= bci->usb_cur_target || + bci->usb_cur + USB_CUR_STEP > USB_MAX_CURRENT) { + /* Reached target and voltage is OK - stop */ + return; + } else { + bci->usb_cur += USB_CUR_STEP; + schedule_delayed_work(&bci->current_worker, USB_CUR_DELAY); + } + twl4030_charger_update_current(bci); +} + /* * Enable/Disable USB Charge functionality. */ @@ -451,6 +504,7 @@ static int twl4030_charger_enable_usb(struct twl4030_bci *bci, bool enable) pm_runtime_put_autosuspend(bci->transceiver->dev); bci->usb_enabled = 0; } + bci->usb_cur = 0; } return ret; @@ -599,7 +653,7 @@ twl4030_bci_max_current_store(struct device *dev, struct device_attribute *attr, if (dev == &bci->ac->dev) bci->ac_cur = cur; else - bci->usb_cur = cur; + bci->usb_cur_target = cur; twl4030_charger_update_current(bci); return n; @@ -621,7 +675,7 @@ static ssize_t twl4030_bci_max_current_show(struct device *dev, cur = bci->ac_cur; } else { if (bci->ac_is_active) - cur = bci->usb_cur; + cur = bci->usb_cur_target; } if (cur < 0) { cur = twl4030bci_read_adc_val(TWL4030_BCIIREF1); @@ -662,9 +716,9 @@ static int twl4030_bci_usb_ncb(struct notifier_block *nb, unsigned long val, /* reset current on each 'plug' event */ if (allow_usb) - bci->usb_cur = 500000; + bci->usb_cur_target = 500000; else - bci->usb_cur = 100000; + bci->usb_cur_target = 100000; bci->event = val; schedule_work(&bci->work); @@ -927,9 +981,9 @@ static int twl4030_bci_probe(struct platform_device *pdev) bci->ichg_hi = 500000; /* High threshold */ bci->ac_cur = 500000; /* 500mA */ if (allow_usb) - bci->usb_cur = 500000; /* 500mA */ + bci->usb_cur_target = 500000; /* 500mA */ else - bci->usb_cur = 100000; /* 100mA */ + bci->usb_cur_target = 100000; /* 100mA */ bci->usb_mode = CHARGE_AUTO; bci->ac_mode = CHARGE_AUTO; @@ -980,6 +1034,7 @@ static int twl4030_bci_probe(struct platform_device *pdev) } INIT_WORK(&bci->work, twl4030_bci_usb_work); + INIT_DELAYED_WORK(&bci->current_worker, twl4030_current_worker); bci->usb_nb.notifier_call = twl4030_bci_usb_ncb; if (bci->dev->of_node) { -- 2.20.1