From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753296AbcAMSpI (ORCPT ); Wed, 13 Jan 2016 13:45:08 -0500 Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.218]:15209 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751081AbcAMSpG convert rfc822-to-8bit (ORCPT ); Wed, 13 Jan 2016 13:45:06 -0500 X-RZG-AUTH: :JGIXVUS7cutRB/49FwqZ7WcKdUCnXG6JabOfSXKWrat9gtPvwuWM X-RZG-CLASS-ID: mo00 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Subject: Re: [PATCH 1/3] ARM: dts: omap5-board-common: enable rtc and charging of backup battery From: "H. Nikolaus Schaller" In-Reply-To: <56969800.5010206@ti.com> Date: Wed, 13 Jan 2016 19:44:55 +0100 Cc: Tony Lindgren , Grygorii Strashko , Laxman Dewangan , =?windows-1252?Q?Beno=EEt_Cousson?= , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Russell King , linux-omap , devicetree@vger.kernel.org, LKML , Marek Belisko , =?windows-1252?Q?Gra=9Evydas_Ignotas?= , Keerthy Content-Transfer-Encoding: 8BIT Message-Id: References: <20160111202421.GA12777@atomide.com> <20160112000917.GC12777@atomide.com> <417BBA32-A7DC-40CD-8A6B-EA910B1C9C13@goldelico.com> <001346CD-CF31-4FEF-B406-B89EEBDFA063@goldelico.com> <56966558.1070608@ti.com> <569669C5.2070200@ti.com> <20160113164856.GF12777@atomide.com> <5696896F.4090309@ti.com> <20160113180006.GJ12777@atomide.com> <2B99611A-5D2E-4D17-A17D-0150516109FD@goldelico.com> <56969800.5010206@ti.com> To: Nishanth Menon X-Mailer: Apple Mail (2.1878.6) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 13.01.2016 um 19:31 schrieb Nishanth Menon : > On 01/13/2016 12:08 PM, H. Nikolaus Schaller wrote: > [...] > >>> OK. So are we sure the TWL driver will never have to toggle this pin? >> >> After studying the Palmas TRM it appears that this pin just should be "high" >> to be able to write to RTC and some scratchpad register. If the Palmas OTP >> is programmed to use gpio7 as msecure input. > > Thanks for digging it up. we dont use the scratchpad, but in some cases > where SoC cold reset is involved, those registers may store additional > information. I remember a similar thing from omap3-twl4030 where the boot source is stored so that a warm reboot searches there. But I don#t know if the OMPAP5 Boot ROM is using that. > >> >> Since the scratchpad is not used we can permanently enable msecure. Which >> means that we must somehow get the driving output to be "1". >> >> This can be either done by >> * a gpio with pull-up - switched to input mode as I proposed, or > > I think you intended to suggest to do a mux to gpio with just pinmux > pull? Yes. > The internal pull on padconf is very weak > - for typical needs like > these, it is rather suggested to stick with real GPIO drive to prevent > conditions like noise interference(for example). well, on OMAP5 pull up/down are astonishingly strong :) 100-250ľA. Which translated roughly to 7 .. 18 kOhm @ 1.8V logic. So a noise source must be coupled by an impedance in the 1 kOhm range. This is quite rare. So I would not worry about that. But if there is MUX_MODE1 for this purpose that works equally well, we should use it instead of a gpin+pullup. BR, Nikolaus From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Nikolaus Schaller" Subject: Re: [PATCH 1/3] ARM: dts: omap5-board-common: enable rtc and charging of backup battery Date: Wed, 13 Jan 2016 19:44:55 +0100 Message-ID: References: <20160111202421.GA12777@atomide.com> <20160112000917.GC12777@atomide.com> <417BBA32-A7DC-40CD-8A6B-EA910B1C9C13@goldelico.com> <001346CD-CF31-4FEF-B406-B89EEBDFA063@goldelico.com> <56966558.1070608@ti.com> <569669C5.2070200@ti.com> <20160113164856.GF12777@atomide.com> <5696896F.4090309@ti.com> <20160113180006.GJ12777@atomide.com> <2B99611A-5D2E-4D17-A17D-0150516109FD@goldelico.com> <56969800.5010206@ti.com> Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <56969800.5010206-l0cyMroinI0@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Nishanth Menon Cc: Tony Lindgren , Grygorii Strashko , Laxman Dewangan , =?windows-1252?Q?Beno=EEt_Cousson?= , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Russell King , linux-omap , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, LKML , Marek Belisko , =?windows-1252?Q?Gra=9Evydas_Ignotas?= , Keerthy List-Id: devicetree@vger.kernel.org Am 13.01.2016 um 19:31 schrieb Nishanth Menon : > On 01/13/2016 12:08 PM, H. Nikolaus Schaller wrote: > [...] >=20 >>> OK. So are we sure the TWL driver will never have to toggle this pi= n? >>=20 >> After studying the Palmas TRM it appears that this pin just should b= e "high" >> to be able to write to RTC and some scratchpad register. If the Palm= as OTP >> is programmed to use gpio7 as msecure input. >=20 > Thanks for digging it up. we dont use the scratchpad, but in some cas= es > where SoC cold reset is involved, those registers may store additiona= l > information. I remember a similar thing from omap3-twl4030 where the boot source is = stored so that a warm reboot searches there. But I don#t know if the OMPAP5 Bo= ot ROM is using that. >=20 >>=20 >> Since the scratchpad is not used we can permanently enable msecure. = Which >> means that we must somehow get the driving output to be "1". >>=20 >> This can be either done by >> * a gpio with pull-up - switched to input mode as I proposed, or >=20 > I think you intended to suggest to do a mux to gpio with just pinmux > pull? Yes. > The internal pull on padconf is very weak > - for typical needs like > these, it is rather suggested to stick with real GPIO drive to preven= t > conditions like noise interference(for example). well, on OMAP5 pull up/down are astonishingly strong :) 100-250=B5A. Which translated roughly to 7 .. 18 kOhm @ 1.8V logic. So a noise source must be coupled by an impedance in the 1 kOhm range. This is quite rare. So I would not worry about that. But if there is MUX_MODE1 for this purpose that works equally well, we should use it instead of a gpin+pullup. BR, Nikolaus-- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html