| Message ID | 20150224043353.4243.32335.stgit@notabene.brown (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Tue 2015-02-24 15:33:53, NeilBrown wrote: > 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 configure Standard Downstream Port, it may not be possible > to reliably pull 500mA - depending on cable quality and source "configured"? > quality I have reports of charging failure due to the voltage dropping > too low. > > To address both these concern, this patch introduce incremental concerns. > 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 long, the target current is reduced "too low"? > 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 1.7mA imposed by the > hardware. 1.7A? > @@ -249,8 +261,14 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) > cur = bci->ac_cur; > bci->ac_is_active = 1; > } else { > - cur = bci->usb_cur; > + cur = bci->usb_cur_actual; usb_cur_actual is not a really great variable name... > bci->ac_is_active = 0; > + if (cur > bci->usb_cur) { > + cur = bci->usb_cur; > + bci->usb_cur_actual = cur; > + } > + if (cur < bci->usb_cur) > + schedule_delayed_work(&bci->current_worker, USB_CUR_DELAY); > } > > /* First, check thresholds and see if cgain is needed */ > @@ -379,6 +397,38 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) > return 0; > } > > +static void twl4030_current_worker(struct work_struct *data) > +{ > + int v; > + 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; > + > + printk("v=%d cur=%d target=%d\n", v, bci->usb_cur_actual, > + bci->usb_cur); > + > + if (v < USB_MIN_VOLT) { > + /* Back up and stop adjusting. */ > + bci->usb_cur_actual -= USB_CUR_STEP; > + bci->usb_cur = bci->usb_cur_actual; > + } else if (bci->usb_cur_actual >= bci->usb_cur || > + bci->usb_cur_actual + USB_CUR_STEP > USB_MAX_CURRENT) { > + /* Reach target and volts are OK - stop */ Reached ... and the voltage is OK - stop.
On Mon, 2 Mar 2015 22:29:45 +0100 Pavel Machek <pavel@ucw.cz> wrote: > On Tue 2015-02-24 15:33:53, NeilBrown wrote: > > 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 configure Standard Downstream Port, it may not be possible > > to reliably pull 500mA - depending on cable quality and source > > "configured"? > > > quality I have reports of charging failure due to the voltage dropping > > too low. > > > > To address both these concern, this patch introduce incremental > > concerns. > > > 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 long, the target current is reduced > > "too low"? > > > 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 1.7mA imposed by the > > hardware. > > 1.7A? > > > > @@ -249,8 +261,14 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) > > cur = bci->ac_cur; > > bci->ac_is_active = 1; > > } else { > > - cur = bci->usb_cur; > > + cur = bci->usb_cur_actual; > > usb_cur_actual is not a really great variable name... I changed "usb_cur" to "usb_cur_target" and "usb_cur_actual" to "usb_cur". > > > bci->ac_is_active = 0; > > + if (cur > bci->usb_cur) { > > + cur = bci->usb_cur; > > + bci->usb_cur_actual = cur; > > + } > > + if (cur < bci->usb_cur) > > + schedule_delayed_work(&bci->current_worker, USB_CUR_DELAY); > > } > > > > /* First, check thresholds and see if cgain is needed */ > > @@ -379,6 +397,38 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) > > return 0; > > } > > > > +static void twl4030_current_worker(struct work_struct *data) > > +{ > > + int v; > > + 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; > > + > > + printk("v=%d cur=%d target=%d\n", v, bci->usb_cur_actual, > > + bci->usb_cur); > > + > > + if (v < USB_MIN_VOLT) { > > + /* Back up and stop adjusting. */ > > + bci->usb_cur_actual -= USB_CUR_STEP; > > + bci->usb_cur = bci->usb_cur_actual; > > + } else if (bci->usb_cur_actual >= bci->usb_cur || > > + bci->usb_cur_actual + USB_CUR_STEP > USB_MAX_CURRENT) { > > + /* Reach target and volts are OK - stop */ > > Reached ... and the voltage is OK - stop. > > Thanks for all your proof-reading :-) NeilBrown
diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c index e5a0225ea87e..7ad6b4b531d7 100644 --- a/drivers/power/twl4030_charger.c +++ b/drivers/power/twl4030_charger.c @@ -117,6 +117,18 @@ 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 set back one + * step. + */ + int usb_cur_actual; + 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 1.7mA */ + unsigned long event; }; @@ -249,8 +261,14 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) cur = bci->ac_cur; bci->ac_is_active = 1; } else { - cur = bci->usb_cur; + cur = bci->usb_cur_actual; bci->ac_is_active = 0; + if (cur > bci->usb_cur) { + cur = bci->usb_cur; + bci->usb_cur_actual = cur; + } + if (cur < bci->usb_cur) + schedule_delayed_work(&bci->current_worker, USB_CUR_DELAY); } /* First, check thresholds and see if cgain is needed */ @@ -379,6 +397,38 @@ static int twl4030_charger_update_current(struct twl4030_bci *bci) return 0; } +static void twl4030_current_worker(struct work_struct *data) +{ + int v; + 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; + + printk("v=%d cur=%d target=%d\n", v, bci->usb_cur_actual, + bci->usb_cur); + + if (v < USB_MIN_VOLT) { + /* Back up and stop adjusting. */ + bci->usb_cur_actual -= USB_CUR_STEP; + bci->usb_cur = bci->usb_cur_actual; + } else if (bci->usb_cur_actual >= bci->usb_cur || + bci->usb_cur_actual + USB_CUR_STEP > USB_MAX_CURRENT) { + /* Reach target and volts are OK - stop */ + return; + } else { + bci->usb_cur_actual += USB_CUR_STEP; + schedule_delayed_work(&bci->current_worker, USB_CUR_DELAY); + } + twl4030_charger_update_current(bci); +} + /* * Enable/Disable USB Charge functionality. */ @@ -441,6 +491,7 @@ 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_actual = 0; } return ret; @@ -972,6 +1023,7 @@ static int __init 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) {
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 configure 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 concern, 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 long, 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 1.7mA imposed by the hardware. Signed-off-by: NeilBrown <neilb@suse.de> --- drivers/power/twl4030_charger.c | 54 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 53 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html