Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752309Ab3FEHBr (ORCPT ); Wed, 5 Jun 2013 03:01:47 -0400 Received: from mail-ie0-f175.google.com ([209.85.223.175]:53422 "EHLO mail-ie0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682Ab3FEHBp convert rfc822-to-8bit (ORCPT ); Wed, 5 Jun 2013 03:01:45 -0400 MIME-Version: 1.0 In-Reply-To: <201306041405.13320.heiko@sntech.de> References: <201306030055.15413.heiko@sntech.de> <201306030059.47611.heiko@sntech.de> <201306041405.13320.heiko@sntech.de> Date: Wed, 5 Jun 2013 09:01:44 +0200 Message-ID: Subject: Re: [PATCH 07/10] pinctrl: add pinctrl driver for Rockchip SoCs From: Linus Walleij To: =?ISO-8859-1?Q?Heiko_St=FCbner?= Cc: Stephen Warren , Laurent Pinchart , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , John Stultz , Thomas Gleixner , Mike Turquette , Seungwon Jeon , Jaehoon Chung , Chris Ball , "linux-mmc@vger.kernel.org" , Grant Likely , Rob Herring , "devicetree-discuss@lists.ozlabs.org" , Russell King , Arnd Bergmann , Olof Johansson Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2882 Lines: 78 On Tue, Jun 4, 2013 at 2:05 PM, Heiko St?bner wrote: >> > +PULL_AUTO (1 << 0): indicate this pin needs a pull setting for SoCs >> > + that determine the pull up or down themselfs >> >> Hm, never saw that before... > > Citing the original gpio driver: > > /* > * Values written to this register independently > * control Pullup/Pulldown or not for the > * corresponding data bit in GPIO. > * 0: pull up/down enable, PAD type will decide > * to be up or down, not related with this value > * 1: pull up/down disable > */ > > So if it's a pull up or down is decided based on the mux of the pin. Calling > everything a "pull down" (or up) when it isn't seemed somehow wrong to me. > > The rk3188 on the other hand supports both pull up and down separately. > > Or should this be selected as PULL_UP | PULL_DOWN in the config? The generic config is pretty much either/or so it'd be a new config for that approach. Basically it seems they have embedded knowledge into the silicon: there is no specific rule as to whether a pad should be pulled up or down depending on "pad type" as is stated, rather it's so that if you know a pad will be used for I2C SCL then you know it needs pull-up. Probably something like a "1" on some constant switch in VHDL/Verilog is hard-coded into the silicon turning on pull-up if I2C is selected and the autopull is set for example. >> +config PINCTRL_ROCKCHIP >> + bool >> + select PINMUX >> + select PINCONF >> + select GENERIC_IRQ_CHIP >> >> Why is this super-simple pin config thing not using >> GENERIC_PINCONF? >> >> I *know* it is simpler to implement your own thing, but think of the >> poor maintainers that have to wade through 50 identical implementations. >> Do this, it pays off. > > generic pinconf sounds interesting ... will give it a try. > > The only problem is the pull stuff mentioned above that is either pull up or > down without the driver having knowledge about it. And generic_pinconf only > knows about them separately right now. Create a separate patch adding PIN_CONFIG_BIAS_PULL_AUTO to include/linux/pinctrl/pinconf-generic.h, don't forget the kerneldoc, and patching drivers/pinctrl/pinconf-generic.c. I'll apply it right away. >> Nothing else you want to say about the pins here? >> (No big deal for sure, but....) > > when using pinconfig_generic, its dump_pin function should be more talkative > right? Yes, one of the things you get for free... soon also the pin config DT parser will be for free I hope. Yours, Linus Walleij -- 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/