Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933353AbcKHLdo (ORCPT ); Tue, 8 Nov 2016 06:33:44 -0500 Received: from szxga01-in.huawei.com ([58.251.152.64]:49155 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933258AbcKHLc7 (ORCPT ); Tue, 8 Nov 2016 06:32:59 -0500 Subject: Re: [PATCH v1 03/11] drivers: soc: hisi: Add support for Hisilicon Djtag driver To: Arnd Bergmann References: <1478101374-18778-1-git-send-email-anurup.m@huawei.com> <2127881.qmAR1XgW9F@wuerfel> <2a8dc40f-be75-b010-3ec7-6912f02e3c90@huawei.com> <2467231.EbVekJun1R@wuerfel> CC: , Anurup M , , , , , , , , , , , , From: John Garry Message-ID: Date: Tue, 8 Nov 2016 11:23:35 +0000 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <2467231.EbVekJun1R@wuerfel> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.181.151] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2019 Lines: 64 On 07/11/2016 20:08, Arnd Bergmann wrote: > On Monday, November 7, 2016 2:15:10 PM CET John Garry wrote: >> >> Hi Arnd, >> >> The new bus type tries to model the djtag in a similar way to I2C/USB >> driver arch, where we have a host bus adapter and child devices attached >> to the bus. The child devices are bus driver devices and have bus >> addresses. We think of the djtag as a separate bus, so we are modelling >> it as such. >> >> The bus driver offers a simple host interface for clients to read/write >> to the djtag bus: bus accesses are hidden from the client, the host >> drives the bus. > > Ok, in that case we should probably start out by having a bus specific > DT binding, and separating the description from that of the bus master > device. OK > > I'd suggest requiring #address-cells=<1> and #size-cells=<0> in the master > node, and listing the children by reg property. If the address is not > easily expressed as a single integer, use a larger #address-cells value. We already have something equivalent to reg in "module-id" (see patch 02/11), which is the slave device bus address; here's a sample: + /* For L3 cache PMU */ + pmul3c0 { + compatible = "hisilicon,hisi-pmu-l3c-v1"; + scl-id = <0x02>; + num-events = <0x16>; + num-counters = <0x08>; + module-id = <0x04>; + num-banks = <0x04>; + cfgen-map = <0x02 0x04 0x01 0x08>; + counter-reg = <0x170>; + evctrl-reg = <0x04>; + event-en = <0x1000000>; + evtype-reg = <0x140>; + }; FYI, "module-id" is our own internal hw nomenclature. > > Another option that we have previously used was to actually pretend that > a vendor specific bus is an i2c bus and use the i2c probing infrastructure, > but that only makes sense if the software side closely resembles i2c > (this was the case for Allwinner I think, but I have not looked at > your driver in enough detail to know if it is true here as well). > OK, let me check this. By chance do you remember the specific AllWinner driver/hw? Cheers, John > Arnd > > . >