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=-0.8 required=3.0 tests=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 17FA3C433DF for ; Mon, 25 May 2020 08:23:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F38AB2068D for ; Mon, 25 May 2020 08:23:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731353AbgEYIXW (ORCPT ); Mon, 25 May 2020 04:23:22 -0400 Received: from mail-oi1-f196.google.com ([209.85.167.196]:40463 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725849AbgEYIXV (ORCPT ); Mon, 25 May 2020 04:23:21 -0400 Received: by mail-oi1-f196.google.com with SMTP id v128so15405092oia.7; Mon, 25 May 2020 01:23:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=28/BUMdFhJjxsxR1feXVFplXDlF+r6hoIsh+I+AzW0E=; b=un18HYLQ7z1tPBCJLUfcvJDsi35hNSYl70745bPTOjIqRFwBqT21L1VEvBnmIrMyJC hX7zM0pXtbr/lq7fLTGja1BxlJks+1zpFuBL5GZtKDXW0RZhQG6uxAg34mZUEuKbAOiy /KbCfmgzRroOCaU7HQKTC12P5T3w4GD9Eo7vuipUFQkM6WlwdYIF+N0rkGyxPpcZJcuL dSzQMLjA8WZaM589mIUJxrmnaFtfFk6im8MvLjkb6BVhbGcUp/oAVSWY0PiweHHgxwTH hHbFjVqpidmvwkDE7i+bIN53RQ7Ok4+tr0let3cL9FztTh8UKABiHE2SEW6+A2axIpSv 4TGw== X-Gm-Message-State: AOAM5328wcEyAYZb3Z8l6FqeHHpp74wDlvXzCSBRRld9AUP2Tbe6wgPb 2CJ+rIRNriAXfyEyg/SadlSdsnwKjczhH8H3qDcqLnEo X-Google-Smtp-Source: ABdhPJyzr0dnWV3MxYv2OKruE8IEE6eIwSdF+vupDK8Z/lgVCl750YPGIPHRJxBhyO31YeNKh1PTPnPf9gE6bcsIQIk= X-Received: by 2002:aca:cd93:: with SMTP id d141mr9968926oig.148.1590394999938; Mon, 25 May 2020 01:23:19 -0700 (PDT) MIME-Version: 1.0 References: <1589555337-5498-1-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com> <1589555337-5498-4-git-send-email-prabhakar.mahadev-lad.rj@bp.renesas.com> <20200515171031.GB19423@ninjato> <20200518092601.GA3268@ninjato> <20200522201727.GA21376@ninjato> In-Reply-To: <20200522201727.GA21376@ninjato> From: Geert Uytterhoeven Date: Mon, 25 May 2020 10:23:08 +0200 Message-ID: Subject: Re: [PATCH 03/17] ARM: dts: r8a7742: Add I2C and IIC support To: Wolfram Sang Cc: "Lad, Prabhakar" , Lad Prabhakar , Jens Axboe , Rob Herring , Ulf Hansson , Sergei Shtylyov , "David S. Miller" , Wim Van Sebroeck , Guenter Roeck , linux-ide@vger.kernel.org, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , LKML , Linux I2C , Linux MMC List , netdev , Linux-Renesas , Linux Watchdog Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-watchdog-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-watchdog@vger.kernel.org Hi Wolfram, On Fri, May 22, 2020 at 10:17 PM Wolfram Sang wrote: > > > According to the Hardware User's Manual Rev. 1.00, the registers do exist > > > on all RZ/G1, except for RZ/G1E (see below). > > > > > > "(automatic transmission can be used as a hardware function, but this is > > > not meaningful for actual use cases)." > > > > > > (whatever that comment may mean?) > > Strange comment, in deed. Given the paragraph before, I would guess Gen1 > maybe had a "fitting" PMIC where SoC/PMIC handled DVFS kind of magically > with this automatic transfer feature? And Gen2 has not. > > > > On R-Car E3 and RZ/G2E, which have a single IIC instance, we > > > handled that by: > > > > > > The r8a77990 (R-Car E3) and r8a774c0 (RZ/G2E) > > > controllers are not considered compatible with > > > "renesas,rcar-gen3-iic" or "renesas,rmobile-iic" > > > due to the absence of automatic transmission registers. > > From a "describe the HW" point of view, this still makes sense to me. > Although, it is unlikely we will add support for the automatic > transmission feature (maybe famous last words). ;-) > > > On R-Car E2 and RZ/G1E, we forgot, and used both SoC-specific and > > > family-specific compatible values. > > Okay, but we can fix DTs when they have bugs, or? We can. But we also have to consider DT backwards compatibility: i.e. using an old DTB with a future kernel implementing the automatic transmission feature. Fortunately R-Car E2 and RZ/G1E have SoC-specific compatible values, so we can easily blacklist it in the driver based on that. Blacklisting the last instance on the other SoCs is uglier, as it needs a quirk that checks both the SoC-compatible value and the absence of the generic compatible value. But it can still be done. Reviewed-by: Geert Uytterhoeven i.e. will queue in renesas-devel for v5.9. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds