Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965558AbbEMPqD (ORCPT ); Wed, 13 May 2015 11:46:03 -0400 Received: from mout.kundenserver.de ([212.227.126.130]:58957 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964839AbbEMPpy (ORCPT ); Wed, 13 May 2015 11:45:54 -0400 From: Arnd Bergmann To: Daniel Thompson Cc: Maxime Coquelin , Uwe =?ISO-8859-1?Q?Kleine=2DK=F6nig?= , Andreas =?ISO-8859-1?Q?F=E4rber?= , Geert Uytterhoeven , Rob Herring , Philipp Zabel , Linus Walleij , Stefan Agner , Peter Meerwald , Paul Bolle , Peter Hurley , Andy Shevchenko , Chanwoo Choi , Russell King , Daniel Lezcano , Joe Perches , Vladimir Zapolskiy , Lee Jones , Jonathan Corbet , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Thomas Gleixner , Greg Kroah-Hartman , Jiri Slaby , Andrew Morton , "David S. Miller" , Mauro Carvalho Chehab , Antti Palosaari , Tejun Heo , Will Deacon , Nikolay Borisov , Rusty Russell , Kees Cook , Michal Marek , "linux-doc@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-gpio@vger.kernel.org" , "linux-serial@vger.kernel.org" , Linux-Arch , "linux-api@vger.kernel.org" , Nicolae Rosia , Kamil Lulko Subject: Re: [PATCH v8 14/16] ARM: dts: Introduce STM32F429 MCU Date: Wed, 13 May 2015 17:28:57 +0200 Message-ID: <11310179.epfRucfQKB@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <55536BC2.30603@linaro.org> References: <1431158038-3813-1-git-send-email-mcoquelin.stm32@gmail.com> <3125409.QXbEmPolyh@wuerfel> <55536BC2.30603@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:qiZdxmH3dkQ2njHOFj3vMlhuXdFnzofEgL9JRWkG2RQvHIHXq0u NPONYVahg2ubxUJISJhuOdIIr+R1MN2E1KwnRTQd0km9fuuvAbUgucVvZwz4GfW2BEonWJq LVcSY6JjzdVdBSufo3tj6N2c11bZWf+RDmJI2x56bclA+ZanHQvyTa9o4mQzuMlXMImbNRy FNkGh9DP8cOZNlP3xiKVw== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4255 Lines: 114 On Wednesday 13 May 2015 16:20:34 Daniel Thompson wrote: > For the all reset bits: > > clock idx = reset idx + 256 > > The opposite is not true; the clock bits are a superset of the reset > bits (the reset bits act on cells but some cells have >1 clock). Ok, in that case, I would strongly recommend subtracting that 256 offset keeping the numbers the same, to remove the function-type macros. > >> However there are a couple of clocks without gating just before the > >> clock reaches the peripheral: > >> > >> 1. A hard coded /8. I think this will have to be given a synthetic > >> number. > > > > If this is just a divider, why not use a separate DT node for that, > > like this: > > > > clock { > > compatible = "fixed-factor-clock"; > > clocks = <&parentclk>; > > #clock-cells = <0>; > > clock-div = <8>; > > clock-mult = <1>; > > }; > > > > No need to assign a number for this. > > I'd wondered about doing that. > > It will certainly work but it seemed a bit odd to me to have one (really > tiny) part of the RCC cell included seperately in the platform > description whilst all the complicated bits end up aggregated into the > RCC cell. > > Is there much prior art that uses this type of trick to avoid having > magic numbers into the bindings? Are you sure that divider is actually part of the RCC? > >> 2. Ungated dividers. For these I am using the bit offset of the LSB of > >> the mux field. > > > > Do these ones also come with resets? > > No. They mostly run to the core and its intimate peripherals (i.e. only > reset line comes from WDT). Ok. > >> So I think there is only one value that is completely unrelated to the > >> hardware and will use a magic constant instead. > >> > >> I had planned to macros similar to the STM32F4_AxB_RESET() family of > >> macros in both clk driver and DT in order to reuse the bit layouts from > >> dt-bindings/mfd/stm32f4-rcc.h . > >> > >> Normal case would have looked like this: > >> > >> timer3: timer@40000000 { > >> compatible = "st,stm32-timer"; > >> reg = <0x40000000 0x400>; > >> interrupts = <28>; > >> resets = <&rcc STM32F4_APB1_RESET(TIM3)>; > >> clocks = <&rcc STM32F4_APB1_CLK(TIM3)>; > >> status = "disabled"; > >> }; > >> > >> Without the macros it looks like this: > >> > >> timer3: timer@40000000 { > >> compatible = "st,stm32-timer"; > >> reg = <0x40000000 0x400>; > >> interrupts = <28>; > >> resets = <&rcc 257>; > >> clocks = <&rcc 513>; > >> status = "disabled"; > >> }; > >> > >> However we could perhaps be more literate even if we don't use the macros? > >> > >> timer3: timer@40000000 { > >> compatible = "st,stm32-timer"; > >> reg = <0x40000000 0x400>; > >> interrupts = <28>; > >> resets = <&rcc ((0x20*8) + 1)>; > >> clocks = <&rcc ((0x40*8) + 1)>; > >> status = "disabled"; > >> }; > > > > How about #address-cells = <2>, so you can do > > > > resets = <&rcc 8 1>; > > clocks = <&rcc 8 1>; > > > > with the first cell being an index for the block and the second cell the > > bit number within that block. > > That would suit me very well (although is the 0x20/0x40 not the 8 that > we would need in the middle column). We don't normally use register offsets in DT. The number 8 here instead would indicate block 8, where each block is four bytes wide. Using the same index here for reset and clock would also help readability. Arnd -- 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/