From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755382AbbLGDIy (ORCPT ); Sun, 6 Dec 2015 22:08:54 -0500 Received: from regular1.263xmail.com ([211.150.99.137]:43540 "EHLO regular1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755067AbbLGDIx (ORCPT ); Sun, 6 Dec 2015 22:08:53 -0500 X-263anti-spam: KSV:0;BIG:0;ABS:1;DNS:0;ATT:0;SPF:S; X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-KSVirus-check: 0 X-ABS-CHECKED: 1 X-SKE-CHECKED: 1 X-ADDR-CHECKED: 0 X-RL-SENDER: zyw@rock-chips.com X-FST-TO: rtc-linux@googlegroups.com X-SENDER-IP: 103.29.142.67 X-LOGIN-NAME: zyw@rock-chips.com X-UNIQUE-TAG: <6eb0a3513380a0b1977eebba1509c6a1> X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Subject: Re: [PATCH] RTC: RK808: Work around hardware bug on November 31st To: Doug Anderson References: <1449107584-3192-1-git-send-email-jwerner@chromium.org> <5664E1CF.8030406@rock-chips.com> Cc: Julius Werner , Andrew Morton , Alessandro Zummo , Sonny Rao , Heiko Stuebner , "linux-kernel@vger.kernel.org" , rtc-linux@googlegroups.com From: Chris Zhong Message-ID: <5664F837.607@rock-chips.com> Date: Mon, 7 Dec 2015 11:08:39 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/07/2015 10:52 AM, Doug Anderson wrote: > Hi, > > On Sun, Dec 6, 2015 at 6:50 PM, Doug Anderson wrote: >> Chris, >> >> On Sun, Dec 6, 2015 at 5:33 PM, Chris Zhong wrote: >>> Hi Doug >>> >>> RK808 has a shadowed register for saving a "frozen" RTC time. >>> When we setting "GET_TIME" to 1, the time will save in this shadowed >>> register. So if we do not set the "GET_TIME", we always get the last time. >>> >>> read the old time before "get_time", and then read the time again for new >>> time. If the old time earlier than 12.1 && new time later than 12.1, we >>> should >>> +1 day for the correct rtc time. >>> >>> On the other hand, we should set the "GET_TIME" after rk808_rtc_set_time, >>> for restore the time before suspend/shut_down. >> Ah, good idea using the shadow registers. The whole point of the >> shadow registers is to enable atomic read of time, right? So if the >> clock ticks as you are reading 23:59:59 you don't end up reading >> 23:59:00 or 24:59:59 (you'll get either 23:59:59 or 24:00:00). So >> right, time read will now be: >> >> 1. Read GET_TIME. Confirm it's 1. >> 2. Read the time. >> 3. Set GET_TIME to 0. >> 4. Set GET_TIME to 1. >> 5. Read the time. >> >> If time from #2 < 11/31 and time from #5 >= 11/31 then we do the >> adjust. If GET_TIME wasn't 1 in step #1 then we won't do any >> adjusting unless the time is actually 11/31. >> >> Between steps #4 and #5 we'll need to add a small delay since old code >> used to use the setting to 0 as a delay (as commented). >> >> We should presumably always leave GET_TIME as 1 unless we're actively >> reading the time for the most reliability. Also, if we've already >> read the time this bootup, we can certainly optimize the above by >> skipping #1 and #2. GET_TIME: Rising transition of this register transfers dynamic registers into static shadowed registers. So only the rising of GET_TIME would update the "static shadowed registers". We only need ensure that the rising occurs on condition that we want to the really time. > Oh, but also we still need to know whether to adjust the alarm. I > think you said that all existing rk808 chips have this bug and that > you'll set a bit (to be determined later) if/when this bug is fixed. > So we still need to assume that all rk808 chips have this bug... I think so, all rk808 chips have this bug. And we can read the version register to differentiate the PMICs, once this bug is fixed. > > -Doug > > > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from regular1.263xmail.com (regular1.263xmail.com. [211.150.99.137]) by gmr-mx.google.com with ESMTPS id pe1si2961797pac.2.2015.12.06.19.09.11 for (version=TLS1 cipher=AES128-SHA bits=128/128); Sun, 06 Dec 2015 19:09:11 -0800 (PST) Subject: [rtc-linux] Re: [PATCH] RTC: RK808: Work around hardware bug on November 31st To: Doug Anderson References: <1449107584-3192-1-git-send-email-jwerner@chromium.org> <5664E1CF.8030406@rock-chips.com> Cc: Julius Werner , Andrew Morton , Alessandro Zummo , Sonny Rao , Heiko Stuebner , "linux-kernel@vger.kernel.org" , rtc-linux@googlegroups.com From: Chris Zhong Message-ID: <5664F837.607@rock-chips.com> Date: Mon, 7 Dec 2015 11:08:39 +0800 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Reply-To: rtc-linux@googlegroups.com List-ID: List-Post: , List-Help: , List-Archive: , List-Unsubscribe: , On 12/07/2015 10:52 AM, Doug Anderson wrote: > Hi, > > On Sun, Dec 6, 2015 at 6:50 PM, Doug Anderson wrote: >> Chris, >> >> On Sun, Dec 6, 2015 at 5:33 PM, Chris Zhong wrote: >>> Hi Doug >>> >>> RK808 has a shadowed register for saving a "frozen" RTC time. >>> When we setting "GET_TIME" to 1, the time will save in this shadowed >>> register. So if we do not set the "GET_TIME", we always get the last time. >>> >>> read the old time before "get_time", and then read the time again for new >>> time. If the old time earlier than 12.1 && new time later than 12.1, we >>> should >>> +1 day for the correct rtc time. >>> >>> On the other hand, we should set the "GET_TIME" after rk808_rtc_set_time, >>> for restore the time before suspend/shut_down. >> Ah, good idea using the shadow registers. The whole point of the >> shadow registers is to enable atomic read of time, right? So if the >> clock ticks as you are reading 23:59:59 you don't end up reading >> 23:59:00 or 24:59:59 (you'll get either 23:59:59 or 24:00:00). So >> right, time read will now be: >> >> 1. Read GET_TIME. Confirm it's 1. >> 2. Read the time. >> 3. Set GET_TIME to 0. >> 4. Set GET_TIME to 1. >> 5. Read the time. >> >> If time from #2 < 11/31 and time from #5 >= 11/31 then we do the >> adjust. If GET_TIME wasn't 1 in step #1 then we won't do any >> adjusting unless the time is actually 11/31. >> >> Between steps #4 and #5 we'll need to add a small delay since old code >> used to use the setting to 0 as a delay (as commented). >> >> We should presumably always leave GET_TIME as 1 unless we're actively >> reading the time for the most reliability. Also, if we've already >> read the time this bootup, we can certainly optimize the above by >> skipping #1 and #2. GET_TIME: Rising transition of this register transfers dynamic registers into static shadowed registers. So only the rising of GET_TIME would update the "static shadowed registers". We only need ensure that the rising occurs on condition that we want to the really time. > Oh, but also we still need to know whether to adjust the alarm. I > think you said that all existing rk808 chips have this bug and that > you'll set a bit (to be determined later) if/when this bug is fixed. > So we still need to assume that all rk808 chips have this bug... I think so, all rk808 chips have this bug. And we can read the version register to differentiate the PMICs, once this bug is fixed. > > -Doug > > > -- -- You received this message because you are subscribed to "rtc-linux". Membership options at http://groups.google.com/group/rtc-linux . Please read http://groups.google.com/group/rtc-linux/web/checklist before submitting a driver. --- You received this message because you are subscribed to the Google Groups "rtc-linux" group. To unsubscribe from this group and stop receiving emails from it, send an email to rtc-linux+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.