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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iclQS-0003Uq-TW; Thu, 05 Dec 2019 07:19:48 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iclQO-0003U6-Sc for linux-arm-kernel@lists.infradead.org; Thu, 05 Dec 2019 07:19:46 +0000 Received: from pty.hi.pengutronix.de ([2001:67c:670:100:1d::c5]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1iclQF-0003vJ-9A; Thu, 05 Dec 2019 08:19:35 +0100 Received: from mfe by pty.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1iclQE-0006xb-J5; Thu, 05 Dec 2019 08:19:34 +0100 Date: Thu, 5 Dec 2019 08:19:34 +0100 From: Marco Felsch To: Stefan =?iso-8859-1?Q?Riedm=FCller?= Subject: Re: [PATCH 1/3] ARM: dts: imx6: phycore-som: fix arm and soc minimum voltage Message-ID: <20191205071934.fkslkkkjuwrnxmbt@pengutronix.de> References: <20191202124200.mvwnsne2vnszyprj@pengutronix.de> <20191202141406.gvzc3lnxefczd33b@pengutronix.de> <20191202145308.7w5pic3fwpq752mz@pengutronix.de> <20191203083307.ntoe2bwha7hzlr42@pengutronix.de> <895eb269794c200e7c04161188787b3933e3ee0c.camel@pengutronix.de> <21bdac21-d5e0-ea84-57b4-5998f64899e9@phytec.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <21bdac21-d5e0-ea84-57b4-5998f64899e9@phytec.de> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 08:15:47 up 19 days, 22:34, 29 users, load average: 0.06, 0.06, 0.02 User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c5 X-SA-Exim-Mail-From: mfe@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191204_231944_925939_6525AA22 X-CRM114-Status: GOOD ( 22.59 ) 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: festevam@gmail.com, shawnguo@kernel.org, chf.fritz@googlemail.com, robh+dt@kernel.org, linux-imx@nxp.com, kernel@pengutronix.de, c.hemp@phytec.de, s.christ@phytec.de, linux-arm-kernel@lists.infradead.org, Lucas Stach Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Stefan, On 19-12-03 13:37, Stefan Riedm=FCller wrote: > Hi Lucas, hi Marco, > = > On 03.12.19 12:44, Lucas Stach wrote: ... > > = > > The DT constraints are supposed to reflect absolute maximum ratings of > > the board design. The regulator driver already knows the limits of the > > PMIC chip, so there is no point in duplicating this information in the > > DT. > > = > > The DT constraints are there to make sure the regulator core can > > constrain the voltage setting to something safe for the specific > > design. A consumer driver bug must never be able to set a voltage that > > is outside of the absolute maximum ratings of _all_ consumers of this > > specific power rail. I know that a lot of DTs get this detail wrong, > > but we shouldn't block patches to fix this. :) > = > Thanks for the clarification and the example. I got it now and will keep = it > in mind for the future. > = > > = > > > > If I have this wrong and the maintainers agree with you could you p= lease > > > > make sure to account for the bypass mode as well since these values= from the > > > > datasheet are valid too? > > > = > > > As I said, the bypass mode isn't supported by the driver and all imx6 > > > based devicetrees follow that case. So we don't have to take that into > > > account. Also we can't meet both contraints with one dt and futhermore > > > the bypass mode decrease your imx6 lifetime due the the increased rip= ple > > > on the arm-core supply. So I think no one wants this setup in the near > > > future. > > = > > As a violation of the minimum voltage setting is very unlikely to cause > > any permanent damage to the design (expect if you got reverse voltage > > flows somewhere) I think it is safe to include the LDO bypass supply > > limits as the lower bound in the DT constraints, even if this mode > > isn't currently used anywhere. > = > Sounds good to me. Okay, I will use the bypass value and add a comment. Stefan can you take a look at the other patches as well? Regards, Marco > Regards, > Stefan > = > > = > > Regards, > > Lucas > > = > = -- = Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel