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[209.132.180.67]) by mx.google.com with ESMTP id m13si37833224pga.331.2019.04.30.08.26.56; Tue, 30 Apr 2019 08:27:13 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726503AbfD3PZz (ORCPT + 99 others); Tue, 30 Apr 2019 11:25:55 -0400 Received: from guitar.tcltek.co.il ([192.115.133.116]:58397 "EHLO mx.tkos.co.il" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725995AbfD3PZz (ORCPT ); Tue, 30 Apr 2019 11:25:55 -0400 Received: from tarshish (unknown [10.0.8.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx.tkos.co.il (Postfix) with ESMTPS id 9C46B44005B; Tue, 30 Apr 2019 18:25:52 +0300 (IDT) References: <20190430093212.28425-1-alexandre.belloni@bootlin.com> <20190430093212.28425-2-alexandre.belloni@bootlin.com> <877ebbu3lz.fsf@tarshish> <20190430114702.GD11339@piout.net> <875zqvu1l3.fsf@tarshish> <20190430130544.GF11339@piout.net> User-agent: mu4e 1.0; emacs 26.1 From: Baruch Siach To: Alexandre Belloni Cc: linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 2/4] rtc: digicolor: set range In-reply-to: <20190430130544.GF11339@piout.net> Date: Tue, 30 Apr 2019 18:25:52 +0300 Message-ID: <87y33rsef3.fsf@tarshish> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alexandre, On Tue, Apr 30 2019, Alexandre Belloni wrote: > On 30/04/2019 15:20:08+0300, Baruch Siach wrote: >> On Tue, Apr 30 2019, Alexandre Belloni wrote: >> > On 30/04/2019 14:36:24+0300, Baruch Siach wrote: >> >> Hi Alexandre, >> >> >> >> On Tue, Apr 30 2019, Alexandre Belloni wrote: >> >> >> >> > While the range of REFERENCE + TIME is actually 33 bits, the counter >> >> > itself (TIME) is a 32-bits seconds counter. >> >> > >> >> > Signed-off-by: Alexandre Belloni >> >> > --- >> >> > drivers/rtc/rtc-digicolor.c | 1 + >> >> > 1 file changed, 1 insertion(+) >> >> > >> >> > diff --git a/drivers/rtc/rtc-digicolor.c b/drivers/rtc/rtc-digicolor.c >> >> > index 5bb14c56bc9a..e6e16aaac254 100644 >> >> > --- a/drivers/rtc/rtc-digicolor.c >> >> > +++ b/drivers/rtc/rtc-digicolor.c >> >> > @@ -206,6 +206,7 @@ static int __init dc_rtc_probe(struct platform_device *pdev) >> >> > platform_set_drvdata(pdev, rtc); >> >> > >> >> > rtc->rtc_dev->ops = &dc_rtc_ops; >> >> > + rtc->rtc_dev->range_max = U32_MAX; >> >> >> >> Where can I find documentation on the meaning and usage of the range_max >> >> value? I could not find anything in the kernel source. >> > >> > It should be set to the maximum UNIX timestamp the RTC can be set to >> > while keeping range_min to range_max contiguous. >> > >> > In the digicolor case, you could go up to 8589934590 (Wed Mar 16 >> > 12:56:30 UTC 2242) but the driver only writes DC_RTC_REFERENCE and I'm >> > not sure it can also update DC_RTC_TIME safely. >> >> DC_RTC_TIME resets to zero whenever dc_rtc_write writes CMD_RESET to the >> DC_RTC_CONTROL register. DC_RTC_REFERENCE keeps the value that >> dc_rtc_write stores there. So the driver will return values larger than >> U32_MAX if you happen to cross this point in time between dc_rtc_write >> and dc_rtc_read. But you can't store a value larger than U32_MAX in >> DC_RTC_REFERENCE. >> >> Will the core RTC code handle the U32_MAX cross correctly? > > Yes, this is ok to return a valid value that is higher than range_max. > However, at that time, you will not be able to set any alarms anymore as > the core doesn't allow to set alarms after range_max. > > I would think that this is fine because this will happen in 2106 and we > have a way to offset the time (the whole goal of setting the range) > using device tree. That's the sort of documentation that I'm missing. The 'start-year' property is mentioned in the DT binding documentation. But I don't see where range_max is documented as a facility for the time offset feature. Anyway, Acked-by: Baruch Siach Thanks, baruch -- http://baruch.siach.name/blog/ ~. .~ Tk Open Systems =}------------------------------------------------ooO--U--Ooo------------{= - baruch@tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -