linux-kernel - Re: [PATCH] rtc: rs5c372: Add RTC_VL_READ, RTC_VL

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Date:   Wed, 10 Nov 2021 16:01:05 +0100
From:   Camel Guo <camelg@...s.com>
To:     Camel Guo <Camel.Guo@...s.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
CC:     Alessandro Zummo <a.zummo@...ertech.it>, kernel <kernel@...s.com>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rtc: rs5c372: Add RTC_VL_READ, RTC_VL_CLR ioctls

Patch V2 has been uploaded. Please review patch v2 instead.

On 11/10/21 3:30 PM, Camel Guo wrote:
> Hello,
> 
> On 11/10/21 3:27 PM, Alexandre Belloni wrote:
>> On 10/11/2021 15:03:49+0100, Camel Guo wrote:
>>> > On 10/11/2021 12:54:54+0100, Camel Guo wrote:
>>> > > From: Camel Guo <camelg@...s.com>
>>> > > +     switch (cmd) {
>>> > > +     case RTC_VL_READ:
>>> > > +             flags = 0;
>>> > > +
>>> > > +             switch (rs5c->type) {
>>> > > +             case rtc_r2025sd:
>>> > > +             case rtc_r2221tl:
>>> > > +                     if ((rs5c->type == rtc_r2025sd && !(ctrl2 & R2x2x_CTRL2_XSTP)) ||
>>> > > +                             (rs5c->type == rtc_r2221tl &&  (ctrl2 & R2x2x_CTRL2_XSTP))) {
>>> > > +                             flags |= RTC_VL_DATA_INVALID;
>>> > > +                     }
>>> > > +                     if (ctrl2 & R2x2x_CTRL2_VDET)
>>> > > +                             flags |= RTC_VL_ACCURACY_LOW;
>>> > 
>>> > Shouldn't that be RTC_VL_BACKUP_LOW?
>>> 
>>> Some drivers (e.g: rv3029_ioctl and rv8803_ioctl) use RTC_VL_ACCURACY_LOW,
>>> but some other drivers (e.g: abx80x_ioctl, pcf2127_rtc_ioctl and
>>> pcf8523_rtc_ioctl) use RTC_VL_BACKUP_LOW instead. Is there any guideline or
>>> document telling the differences between them?
>>> 
>> 
>> RTC_VL_BACKUP_LOW: The backup voltage is low
>> RTC_VL_ACCURACY_LOW: the primary or backup voltage is low, temperature
>> compensation (or similar) has stopped
> 
> Then I agree that we should go for RTC_VL_BACKUP_LOW.
> 
>> 
>> -- 
>> Alexandre Belloni, co-owner and COO, Bootlin
>> Embedded Linux and Kernel engineering
>> https://bootlin.com