Adds 80000 us sleep when the usb cable is plugged in to hopfully avoid bounceing contacts. Upon pluging in the usb cable vbus will bounce for some time, causing cpcap to dissconnect charging due to detecting an undervoltage condition. This is a scope of vbus on xt894 while quickly inserting the usb cable with firm force, probed at the far side of the usb soccet and vbus loaded with approx 1k: http://uvos.xyz/maserati/usbplug.jpg. As can clearly be seen, vbus is all over the place for the first 15 ms or so with a small blip at ~40 ms this causes the cpcap to trip up and disable charging again. The delay helps cpcap_usb_detect avoid the worst of this. It is, however, still not ideal as strong vibrations can cause the issue to reapear at any time during charging. I have however not been able to cause the device to stop charging due to this in practice as it is hard to vibrate the device sutch that the vbus pins start bouncing again but cpcap_usb_detect is not called again due to a detected dissconnect/reconnect event. Changes in v4: Increase timeout after some experiamentation suggested its not sufficant on all devices. Signed-off-by: Carl Philipp Klemm <philipp@xxxxxxxx> --- drivers/power/supply/cpcap-charger.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/power/supply/cpcap-charger.c b/drivers/power/supply/cpcap-charger.c index c0d452e3dc8b..e6b230dd6de4 100644 --- a/drivers/power/supply/cpcap-charger.c +++ b/drivers/power/supply/cpcap-charger.c @@ -613,6 +613,9 @@ static void cpcap_usb_detect(struct work_struct *work) if (error) return; + /* Delay for 80ms to avoid vbus bouncing when usb cable is plugged in */ + usleep_range(80000, 120000); + /* Just init the state if a charger is connected with no chrg_det set */ if (!s.chrg_det && s.chrgcurr1 && s.vbusvld) { cpcap_charger_update_state(ddata, CPCAP_CHARGER_DETECTING); -- 2.29.2
