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Received: from shell.armlinux.org.uk ([fd8f:7570:feb6:1:5054:ff:fe00:4ec]:44858) by pandora.armlinux.org.uk with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1k05Hs-00031S-09; Mon, 27 Jul 2020 16:43:36 +0100 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1k05Hr-0003mQ-5e; Mon, 27 Jul 2020 16:43:35 +0100 Date: Mon, 27 Jul 2020 16:43:35 +0100 From: Russell King - ARM Linux admin To: Alexandre Belloni Subject: Re: [PATCH v2 1/3] dt-bindings: rtc: pcf8523: add DSM pm option for battery switch-over Message-ID: <20200727154335.GL1551@shell.armlinux.org.uk> References: <20200719145028.3370-3-miguelborgesdefreitas@gmail.com> <20200720112401.4620-1-miguelborgesdefreitas@gmail.com> <20200720112401.4620-2-miguelborgesdefreitas@gmail.com> <20200723174905.GA596242@bogus> <20200723195755.GV3428@piout.net> <20200727094553.GH1551@shell.armlinux.org.uk> <20200727144938.GC239143@piout.net> <20200727152439.GK1551@shell.armlinux.org.uk> <20200727154104.GE239143@piout.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200727154104.GE239143@piout.net> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200727_114342_963871_599297D6 X-CRM114-Status: GOOD ( 32.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Rob Herring , baruch@tkos.co.il, kernel@pengutronix.de, a.zummo@towertech.it, festevam@gmail.com, s.hauer@pengutronix.de, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-imx@nxp.com, miguelborgesdefreitas@gmail.com, shawnguo@kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Jul 27, 2020 at 05:41:04PM +0200, Alexandre Belloni wrote: > On 27/07/2020 16:24:39+0100, Russell King - ARM Linux admin wrote: > > On Mon, Jul 27, 2020 at 04:49:38PM +0200, Alexandre Belloni wrote: > > > On 27/07/2020 10:45:53+0100, Russell King - ARM Linux admin wrote: > > > > > This is but this shouldn't be a DT property as it has to be changed > > > > > dynamically. I'm working on an ioctl interface to change this > > > > > configuration. > > > > > > > > Why does it need to be changed dynamically? If the hardware components > > > > are not fitted to allow the RTC to be safely used without DSM, then > > > > why should userspace be able to disable DSM? > > > > > > For RTCs with a standby mode, you want to be able to return to standby > > > mode. > > > > > > That would happen for example after factory flashing in that common use > > > case: > > > - the board is manufactured > > > - Vbackup is installed, the RTC switches to standby mode > > > - the board is then booted to flash a system, Vprimary is now present, > > > the RTC switches to DSM. > > > > > > At this point, if the board is simply shut down, the RTC will start > > > draining Vbackup before leaving the factory. Instead, we want to be able > > > to return to standby mode until the final user switches the product on > > > for the first time. > > > > I don't think you're understanding what's going on with this proposed > > patch. The cubox-i does work today, and the RTC does survive most > > power-downs. There are situations where it doesn't. > > > > So, let's take your process above. > > > > - the board is manufactured > > - Vbackup is installed, the RTC switches to standby mode > > - the board is then booted to flash a system, Vprimary is now present > > - the board is powered down. the RTC _might_ switch over to battery > > if it notices the power failure in time, or it might not. A random > > sample of units leaving the factory have the RTC in standby mode. > > Others are draining the battery. > > > > I'm not saying what you propose isn't a good idea. I'm questioning > > why we should expose this in the generic kernel on platforms where > > it's likely to end up with the RTC being corrupted. > > > > Note that I didn't say we should expose settings that are not working > but it is a different discussion. It isn't a different discussion - that is exactly what the point of my emails to you all along have been! So, can we please have that discussion, it is pertinent to this patch. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last! _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel