From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris BREZILLON Subject: Re: [PATCH 5/5] rtc: at91sam9: add DT bindings documentation Date: Wed, 10 Sep 2014 17:35:32 +0200 Message-ID: <20140910173532.0e8b1ef7@bbrezillon> References: <1409733934-14465-1-git-send-email-boris.brezillon@free-electrons.com> <1409733934-14465-6-git-send-email-boris.brezillon@free-electrons.com> <20140910121424.GG2974@localhost> <20140910152019.111c4c01@bbrezillon> <20140910150702.GK2974@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140910150702.GK2974@localhost> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Johan Hovold Cc: Nicolas Ferre , Jean-Christophe Plagniol-Villard , Alexandre Belloni , Andrew Victor , Alessandro Zummo , rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org On Wed, 10 Sep 2014 17:07:02 +0200 Johan Hovold wrote: > On Wed, Sep 10, 2014 at 03:20:19PM +0200, Boris BREZILLON wrote: > > On Wed, 10 Sep 2014 14:14:24 +0200 > > Johan Hovold wrote: > > > > This does not describe the hardware, but rather a specific software > > > configuration. > > > > > > The RTT is first of all not an RTC (although it can be used as one in a > > > specific software configuration). And the second register resource above > > > is not an RTT register, but a general-purpose backup register could be > > > used for other purposes (which register to use is currently configurable > > > for legacy booting using CONFIG_RTC_DRV_AT91SAM9_GPBR). > > > > We could use a syscon device (which exposes a regmap) for the GPBR > > block. > > > > rtc@ffffff20 { > > rtt > > > compatible = "atmel,at91sam9260-rtt"; > > reg = <0xfffffd20 0x10>; > > interrupts = <1 4 7>; > > clocks = <&clk32k>; > > atmel,time-reg = <&gpbr 0x0>; > > }; > > > > gpbr: syscon@fffffd50 { > > compatible = "atmel,at91sam9260-gpbr", "syscon"; > > reg = <0xfffffd50 0x10>; > > > > }; > > Yes, this essentially what I suggested in the thread (and my last reply) > and relying on syscon rather than a custom driver seems like a good > idea. It would allow early access to the registers too with the recently > proposed changes. It would not guarantee any kind of exclusivity, > though, but I guess that's tolerable? I know about the "mfd: syscon: Decouple syscon interface from platform devices" series, but I wonder why we would need to access GPBR registers during early boot stages. Do you have something in mind :-)? > > Johan -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html