Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751338AbdINHGf (ORCPT ); Thu, 14 Sep 2017 03:06:35 -0400 Received: from ms.tdt.de ([195.243.126.94]:42307 "EHLO mail.dev.tdt.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751132AbdINHGd (ORCPT ); Thu, 14 Sep 2017 03:06:33 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 14 Sep 2017 09:06:30 +0200 From: Florian Eckert To: Rob Herring Cc: Guenter Roeck , Mark Rutland , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Linux HWMON List , Jean Delvare Subject: Re: [PATCH v3 2/2] hwmon: (ltq-cputemp) add devicetree bindings documentation In-Reply-To: References: <20170901065818.2037-1-fe@dev.tdt.de> <20170901065818.2037-2-fe@dev.tdt.de> <20170901142622.GC599@roeck-us.net> <20170912162008.y2dp3llaikkp3l45@rob-hp-laptop> Message-ID: User-Agent: Roundcube Webmail/1.1.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3298 Lines: 124 Hello Rob >>>> > + >>>> > +Requires node properties: >>>> > +- compatible value : >>>> > + "lantiq,cputemp" >>> >>> >>> Kind of non-specific. How is this device even accessed without any >>> other >>> property? >> >> >> It does not need any further properties. If this is set in the device >> tree >> then the driver is loaded. > > DT is not the only way to instantiate drivers. > > What I meant is how do you access the hardware? That should be evident > from the binding and it is not. Agree with our statement. > > Looking at the driver, you have some memory mapped system control > registers which get ioremapped in arch/mips/lantiq/xway/sysctrl.c and > accesses thru some platform specific macros. That is not the ideal way > to do things as we use syscon and regmap for such things. But that's > all mostly kernel details not so relevant to the DT binding. For lanitq xrx200 this is all i have. So if i have to use syscon and regmap i am also not sure how to handle this. > For DT, I'd expect this is a child node of the sysctrl block with a > reg property value of <0x40 4> (along with any other child devices). > You could also not even put this in DT and the system controller can > have it's own driver that instantiates the child device for this > driver. Yes this would be the best practice. But the hardware designer for what ever reason placed the Register for the temperature sensors into the CGU (Clock Generation Unit) section! And the Register is also shared with some other stuff which is not only assign for temperature stuff! I am not sure how to handle this in the device tree. This is a Register description extract from the data sheet GPHY Configuration Register 01 This register configures the booting options of GPHY1 IP. Offset 0x0040 Reset Value 0x01FC0000 31: RES 30: 100FX_H 29: 100FX_F 28: 10BT_F 27: 10BT_H 26: 100BT_F 25: 100BT_H 24: 1000BT_F 23: 1000BT_H 22: RES 21: RES 19: TEMP_PD <--- NEEDED Power down the Temperature Sensor 18: TEMP_HL <--- NEEDED Indicate temperature higher than 128 C 17: TEMP <--- NEEDED Value 16: TEMP <--- NEEDED Value 15: TEMP <--- NEEDED Value 14: TEMP <--- NEEDED Value 13: TEMP <--- NEEDED Value 12: TEMP <--- NEEDED Value 11: TEMP <--- NEEDED Value 10: TEMP <--- NEEDED Value 09: TEMP <--- NEEDED Value 08: RES 07: RES 06: SPI_Delay 05: SPI_Delay 04: AHB_EnD 03: DMA_OR 02: RES 01: RES 00: RES And that is a dts tree from LEDE/Openwrt for lantiq URL: https://github.com/lede-project/source/blob/c88770c766fdc5599efc4672bca230017f52e8e4/target/linux/lantiq/dts/vr9.dtsi#L54 Extraction: sram@1F000000 { #address-cells = <1>; #size-cells = <1>; compatible = "lantiq,sram", "simple-bus"; reg = <0x1F000000 0x800000>; ranges = <0x0 0x1F000000 0x7FFFFF>; eiu0: eiu@101000 { #interrupt-cells = <1>; interrupt-controller; compatible = "lantiq,eiu-xway"; reg = <0x101000 0x1000>; interrupt-parent = <&icu0>; lantiq,eiu-irqs = <166 135 66 40 41 42>; }; pmu0: pmu@102000 { compatible = "lantiq,pmu-xway"; reg = <0x102000 0x1000>; }; cgu0: cgu@103000 { compatible = "lantiq,cgu-xway"; reg = <0x103000 0x1000>; -> This is the place to add the binding? }; Sorry for the noise but i am unsure how to do this. Thanks for help Florian