Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933428AbbLVSRG (ORCPT ); Tue, 22 Dec 2015 13:17:06 -0500 Received: from mail.kernel.org ([198.145.29.136]:56358 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753947AbbLVSRE (ORCPT ); Tue, 22 Dec 2015 13:17:04 -0500 MIME-Version: 1.0 In-Reply-To: <1450613656.15911.62.camel@gmail.com> References: <397668667-27328-3-git-send-email-ynvich@gmail.com> <1450201525-9137-1-git-send-email-ynvich@gmail.com> <20151220033815.GD9883@rob-hp-laptop> <1450613656.15911.62.camel@gmail.com> From: Rob Herring Date: Tue, 22 Dec 2015 12:16:41 -0600 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5] rtc: support DS1302 RTC on ICP DAS LP-8x4x To: Sergei Ianovich Cc: "linux-kernel@vger.kernel.org" , Alexandre Belloni , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Alessandro Zummo , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2676 Lines: 64 On Sun, Dec 20, 2015 at 6:14 AM, Sergei Ianovich wrote: > On Sat, 2015-12-19 at 21:38 -0600, Rob Herring wrote: >> On Tue, Dec 15, 2015 at 08:45:23PM +0300, Sergei Ianovich wrote: [...] >> > diff --git a/Documentation/devicetree/bindings/rtc/rtc-ds1302.txt >> > b/Documentation/devicetree/bindings/rtc/rtc-ds1302.txt >> > new file mode 100644 >> > index 0000000..810613b >> > --- /dev/null >> > +++ b/Documentation/devicetree/bindings/rtc/rtc-ds1302.txt >> > @@ -0,0 +1,14 @@ >> > +* Dallas Semiconductor DS-1302 RTC >> > + >> > +Simple device which could be used to store date/time between >> > reboots. >> > + >> > +Required properties: >> > +- compatible : Should be "dallas,rtc-ds1302" >> > +- reg : Should be address and size of IO memory region >> >> This device is a SPI (or SPI like?) interface. So you have some sort >> of >> of FPGA logic in between the cpu and ds1302. The DT should have a node >> for the controller and then the ds1302 as a child of it. A full blown >> SPI driver may be overkill here, but that's a separate discussion from >> the DT binding. > > Below is the quote from the actual DT of LP-8x4x: >> fpga@5 { >> compatible = "simple-bus"; >> #address-cells = <1>; >> #size-cells = <1>; >> ranges = <0 5 0x3000000 0x10000>; >> interrupt-parent = <&fpgairq>; >> >> rtc@901c { >> compatible = "dallas,rtc-ds1302"; This node should have a LP-8x4x specific compatible and then have a child node for ds1302 that follows the SPI binding. >> reg = <0x901c 0x1>; >> status = "okay"; >> }; > > You are right about the topology. ds1302 is a half-duplex SPI device. > Does this mean I should rewrite the driver to handle the chip as a slave > SPI device, and then provide a master SPI functionality at the FPGA? Well, the binding should reflect that, whether the driver needs to be re-written is somewhat a separate question. That should probably have been done for the DS1302 driver originally and it is not too fair for the 2nd person to fix it. You could just have a single driver bound to the controller node which is aware of the DS1302 being the slave device (ignoring that part of the DT for now). Rob -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/