Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756757AbZGMRe5 (ORCPT ); Mon, 13 Jul 2009 13:34:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756632AbZGMRe5 (ORCPT ); Mon, 13 Jul 2009 13:34:57 -0400 Received: from ru.mvista.com ([213.79.90.228]:63836 "EHLO buildserver.ru.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756559AbZGMRe4 (ORCPT ); Mon, 13 Jul 2009 13:34:56 -0400 Date: Mon, 13 Jul 2009 21:34:55 +0400 From: Anton Vorontsov To: Joakim Tjernlund Cc: David Brownell , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org Subject: Re: [PATCH 0/2] Setting GPIOs simultaneously Message-ID: <20090713173455.GA9866@oksana.dev.rtsoft.ru> Reply-To: avorontsov@ru.mvista.com References: <20090713151911.GA28114@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3473 Lines: 107 On Mon, Jul 13, 2009 at 06:01:02PM +0200, Joakim Tjernlund wrote: > > Anton Vorontsov wrote on 13/07/2009 17:19:11: > > > > Hi all, > > > > I've been sitting on these patches for some time, but now it appears > > that the set_sync() feature is needed elsewhere. So here are the > > patches. > > > > Joakim, I think this is what you need. > > Yes, it sure looks so :) I will have to look closer later as > I will be traveling the next few days. > > Question though, have you considered using a bitmask instead of > an array: > static void qe_gpio_set_sync(struct gpio_chip *gc, unsigned int num, > unsigned int gpio_mask, unsigned int vals) > If you want to set bit 0, 3 and 8 you would set positions 0, 3 and 8 in gpio_mask > to ones. Similarly in vals, set bit positions 0, 3 and 8 to requested value. Yeah, I thought about it. We could do the u64 masks (to handle up to 64 bits parallel IO buses). It's all easy with dumb memory-mapped GPIO controllers, because we have a 8/16/32/64 bits registers with linear bit<->gpio mapping. But some gpio controllers aren't that easy. I know at least one (FPGA-based) gpio controller that won't change any GPIO lines for real unless changes are "commited". The controller has several banks (registers) of PIOs (total count > 64 bits), but you can commit all the changes to the banks at once (synchronously). This isn't because the controller is uber-cool, it's just the controller has sequential IO. So with masks approach you won't able to use _sync() calls that easily for all GPIOs range. But OK, if we throw away the special cases, I can't imagine any clear api for this approach, all I can think of is something along these lines: int num = 3; u32 gpios[3]; u64 shifts[3]; /* this implies checks whether we can use _sync() */ if (!gpio_get_shifts(num, gpios, shifts)) return -EINVAL; gpio_set_values_sync(chip, 1 << shifts[0] | 1 << shifts[1], val0 << shifts[0] | val1 << shifts[1]). We can implement it, if that's acceptable. But that's a bit ugly, I think. > While being at it, the reason for me needing this is that the spi_mpc83xx driver > was recently converted to a OF only driver so I have no way of defining my own > CS function anymore. While OF is good I don't feel that OF drivers should block the native > method, OF should be a layer on top of the native methods. Um, I don't get it. You have a mux, which is a sort of GPIO controller. All you need to do is to write "of-gpio-mux" driver, that will get all the needed gpios from the underlaying GPIO controller. In the device tree it'll look like this: muxed_gpio: gpio-controller { #gpio-cells = <2>; compatible = "board-gpio-mux", "generic-gpio-mux"; gpios = <&qe_pio_d 2 0 /* AD0 */ &qe_pio_d 17 0 /* AD1 */ &qe_pio_d 5 0>; /* AD2 */ gpio-controller; }; spi-controller { gpios = <&muxed_gpio 0 0 &muxed_gpio 1 0 &muxed_gpio 2 0 &muxed_gpio 3 0 &muxed_gpio 4 0 &muxed_gpio 5 0 &muxed_gpio 6 0 &muxed_gpio 7 0>; spi-device@0 { reg = <0>; }; ... spi-device@7 { reg = <0>; }; }; So you don't have to modify the spi driver. Thanks, -- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2 -- 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/