From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755831AbbCBV3w (ORCPT ); Mon, 2 Mar 2015 16:29:52 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:59721 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755406AbbCBV3r (ORCPT ); Mon, 2 Mar 2015 16:29:47 -0500 Date: Mon, 2 Mar 2015 22:29:45 +0100 From: Pavel Machek To: NeilBrown Cc: Samuel Ortiz , Tony Lindgren , Lee Jones , Sebastian Reichel , Dmitry Eremin-Solenikov , David Woodhouse , GTA04 owners , linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 14/15] twl4030_charger: Increase current carefully while watching voltage. Message-ID: <20150302212945.GT13270@amd> References: <20150224043341.4243.23291.stgit@notabene.brown> <20150224043353.4243.32335.stgit@notabene.brown> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150224043353.4243.32335.stgit@notabene.brown> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html