From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4CAA6C433C1 for ; Fri, 19 Mar 2021 21:21:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05D7661974 for ; Fri, 19 Mar 2021 21:21:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230304AbhCSVUz (ORCPT ); Fri, 19 Mar 2021 17:20:55 -0400 Received: from polaris.svanheule.net ([84.16.241.116]:50492 "EHLO polaris.svanheule.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230219AbhCSVU2 (ORCPT ); Fri, 19 Mar 2021 17:20:28 -0400 Received: from [IPv6:2a02:a03f:eaff:9f01:ffbc:9626:10f7:ec57] (unknown [IPv6:2a02:a03f:eaff:9f01:ffbc:9626:10f7:ec57]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: sander@svanheule.net) by polaris.svanheule.net (Postfix) with ESMTPSA id 330A21E0419; Fri, 19 Mar 2021 22:20:25 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=svanheule.net; s=mail1707; t=1616188825; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FJ0oUbr/h/YJU7rB7qgMyRK20DZ+5jtsUgv4ejASZ6Q=; b=9n1lkndbdrHko8zV2k5jLSj8zMhCUaVl4MKTXqscHC+5OQb4AQf7v5mTJp/H99COVyQKsD lN3p9aqF3BnwKURnE0P7fRAtWuBv101UcMBOBIhact/UzMOj6hqQO1e/TKo3JNZthOUaRa MWbn/PVgC00bJWY0QGpx+FMuTj7WAkO0GfYyfOxTrZ2KNLzFvquQlfDmC7kdpn+85OE2Qs zVcgzvs3s6n+S1ut40MYSEs4SvjgxcsukIHqwxIEabrEubD4Qga6jnXdY1OcEvEh/Oh3IK Oo1CSdqjiieVcjnAu9nkcmkn0jlprFqPa1hZaOBJh23wb1Xx240juI09V2xafA== Message-ID: <9d736f272aae42b154a4fdfbcadc1572ee82f516.camel@svanheule.net> Subject: Re: [PATCH v2 2/2] gpio: Add Realtek Otto GPIO support From: Sander Vanheule To: Andy Shevchenko Cc: "open list:GPIO SUBSYSTEM" , devicetree , Linus Walleij , Bartosz Golaszewski , Rob Herring , Thomas Gleixner , Marc Zyngier , Linux Kernel Mailing List , Bert Vermeulen Date: Fri, 19 Mar 2021 22:20:22 +0100 In-Reply-To: References: <20210315082339.9787-1-sander@svanheule.net> <20210315190806.66762-1-sander@svanheule.net> <20210315190806.66762-3-sander@svanheule.net> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.4 (3.38.4-1.fc33) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2021-03-19 at 19:57 +0200, Andy Shevchenko wrote: > On Fri, Mar 19, 2021 at 5:51 PM Sander Vanheule > wrote: > > On Wed, 2021-03-17 at 15:08 +0200, Andy Shevchenko wrote: > > > On Mon, Mar 15, 2021 at 11:11 PM Sander Vanheule < > > > sander@svanheule.net> wrote: > > ... > > > > > +#include > > > > > > Not sure why you need this? See below. > > > > > +       return swab32(readl(ctrl->base + > > > > REALTEK_GPIO_REG_ISR)); > > > > > > Why swab?! How is this supposed to work on BE CPUs? > > > Ditto for all swabXX() usage. > > > > My use of swab32/swahw32 has little to do with the CPU being BE or > > LE, > > but more with the register packing in the GPIO peripheral. > > > > The supported SoCs have port layout A-B-C-D in the registers, where > > firmware built with Realtek's SDK always denotes A0 as the first > > GPIO > > line. So bit 24 in a register has the value for A0 (with the > > exception > > of the IMR register). > > > > I wrote these wrapper functions to be able to use the BIT() macro > > with > > the GPIO line number, similar to how gpio-mmio uses ioread32be() > > when > > the BGPIOF_BIG_ENDIAN_BYTE_ORDER flag is used. > > > > For the IMR register, port A again comes first, but is now 16 bits > > wide > > instead of 8, with A0 at bits 16:17. That's why swahw32 is used for > > this register. > > > > On the currently unsupported RTL9300-series, the port layout is > > reversed: D-C-B-A. GPIO line A0 is then at bit 0, so the swapping > > functions won't be required. When support for this alternate port > > layout is added, some code will need to be added to differentiate > > between the two cases. > > Yes, you have different endianess on the hardware level, why not to > use the proper accessors (with or without utilization of the above > mentioned BGPIOF_BIG_ENDIAN_BYTE_ORDER)? The point I was trying to make, is that it isn't an endianess issue. I shouldn't have used a register with single byte values to try to illustrate that. Consider instead the interrupt masking registers. To write the IMR bits for port A (GPIO 0-7), a 16-bit value must be written. This value (e.g. u16 port_a_imr) is always BE, independent of the packing order of the ports in the registers: // On RTL8380: port A is in the upper word writew(port_a_imr, base + OFFSET_IMR_AB); // On RTL9300: port A is in the lower word writew(port_a_imr, base + OFFSET_IMR_AB + 2); I want the low GPIO lines to be in the lower half-word, so I can manipulate GPIO lines 0-15 with simple mask and shift operations. It just so happens, that all registers needed by bgpio_init contain single-byte values. With BGPIO_BIG_ENDIAN_BYTE_ORDER the port order is reversed as required, but it's a bit of a misnomer here. Best, Sander