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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 92413C433FE for ; Thu, 23 Sep 2021 18:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 717F0611B0 for ; Thu, 23 Sep 2021 18:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242682AbhIWSHa (ORCPT ); Thu, 23 Sep 2021 14:07:30 -0400 Received: from mail-vk1-f178.google.com ([209.85.221.178]:36797 "EHLO mail-vk1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242667AbhIWSHZ (ORCPT ); Thu, 23 Sep 2021 14:07:25 -0400 Received: by mail-vk1-f178.google.com with SMTP id t186so2958974vkd.3; Thu, 23 Sep 2021 11:05:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rBW9oigA3M6I4upMBiJaZfcaxJFLLXlzf1RS4A+4bEM=; b=v7JTG6jI62sNgdD2hmwhceOWpa3fdbufHVNZ6EpFNto4XgAqve2nApiBbpEL9wG+Uv dSL1pWV5Kzh/Cn8Zo/yikumhZaebzNBi7k22vKAsuICC9W9bYh3ipiRbanSE++PNAeYE 5pOFakcbfIW+sA9ilrVLF/FUrsyo5k6RtQdtwy645684QFkT+cFl97ckygx9CDMhAuQQ ZY95kAoKZRWsr8MN4B5lgzNtBqB6xSTzk4DTt21rYRjKYej0X/rIyLtnQFjUjT7hcTZB 2bXSfnN+BoiC+xoh9SjKrwDvsXFIzdsZgAbnIzX6V4ntD2S0d7W2fKmJzP7Xo2CSSKZ+ WnUA== X-Gm-Message-State: AOAM531EtcUB/vGt0Ixu4goIdEH95qTUSF7bDvbOH/6i0vp1pwbY1S0A 4JgVnySrCusRuhaGuT47qm1W0epmDUZjiZ3QkH4= X-Google-Smtp-Source: ABdhPJz4AjvCw8fTJexqs6DkYP0oJBEeFwh+VuYL7GrwofLh9foa4aAVcIhkOm69AWOZpHSirP8hK3g44fRmA8vVrlY= X-Received: by 2002:a1f:9187:: with SMTP id t129mr4910403vkd.15.1632420352877; Thu, 23 Sep 2021 11:05:52 -0700 (PDT) MIME-Version: 1.0 References: <20210920190350.3860821-1-willmcvicker@google.com> <20210920190350.3860821-3-willmcvicker@google.com> <2b48a41a-9130-b4cc-40d3-0bc7930ac76a@canonical.com> In-Reply-To: From: Geert Uytterhoeven Date: Thu, 23 Sep 2021 20:05:41 +0200 Message-ID: Subject: Re: [PATCH v1 2/4] soc: samsung: change SOC_SAMSUNG default config logic To: Lee Jones Cc: Krzysztof Kozlowski , Will McVicker , Catalin Marinas , Will Deacon , "Cc: Android Kernel" , Linux ARM , Linux Kernel Mailing List , linux-samsung-soc , Greg KH Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 23, 2021 at 6:19 PM Geert Uytterhoeven wrote: > On Thu, Sep 23, 2021 at 3:42 PM Lee Jones wrote: > > On Thu, 23 Sep 2021, Krzysztof Kozlowski wrote: > > > On 23/09/2021 14:39, Lee Jones wrote: > > > > As I've explained before, the trigger for all of this was > > > > SERIAL_SAMSUNG which is required for early console on supported > > > > Samsung platforms i.e. this symbol *has* to be built-in. > > > > > > Actually SERIAL_SAMSUNG does not have to be built-in. It is necessary > > > for built-in only for debugging or development, not for real products. > > > > Right. And in the early stages, GKI is used for early (non-released) > > H/W (this is also the part of the reason these differences can't be > > upstreamed early/now/yet) and sometimes changes break things requiring > > low-level debugging techniques to solve (inc. early console). > > > > > Unlike other drivers which have to be built-in, e.g. clocks or pinctrl, > > > or heavily tested whether setup from initrd works. Plus not breaking > > > distros who like to have everything as module (solution from Geert?)... > > > > We don't know which drivers *need* to be built-in yet. > > > > Clocks is probably not a good example even, since the power-on default > > is most likely all-on, which is fine. Pinctrl remains to be seen. > > Clocks is an excellent example: if a clock is missing, the driver > will fail to probe (unless the clock is considered optional by > the driver), regardless of the power-on or boot loader defaults. > With fw_devlinks=on (which is the default now, and developed by a > Google engineer (GKI or another division?)), the driver won't even > get to the probing point. > > Pinctrl is different, as unless I'm mistaken, drivers will still > probe if the pin control driver is missing, so they will work if the > power-on or boot loader defaults of pin control are fine. In addition, relying on implicit power-on or boot loader state comes with its own set of pitfalls, which may break other use cases. On a heavily power-managed mobile device, clocks and/or power domains can be turned off, so a kernel launched from kexec or kdump may start in a state not adhering to these implicit dependencies. 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 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=-5.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 DE32BC433F5 for ; Thu, 23 Sep 2021 18:08:26 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B19B1611B0 for ; Thu, 23 Sep 2021 18:08:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B19B1611B0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=VefSeFu45046sNb512Zup64t/SXbFM+oyLIkxm0vFes=; b=yDj89QFYadrQr6 HnIJlaacSkE/8liMgOQuX/WlkUVGoJYxd+t20g4YQP4O8bJ0TJ/zZn1mUHoIk7VbUe/Dr7b1TILmM K1eQBUwCzl3ehn47mTv6TN46hDWtdnZuUITpcd38Lm0xyAGR6I6ISaOWqY5VkOaVTncvqnko15OHW 8Ju1jlDIBDExjD8E1bOfWY9u9dXfravFNACWgkMM6lPL5tebUCByZ0WHtNc2rlARIXJvSDHopr4Vq 0iTk1G4CP2pW2AKv6bpEeDT2x10yV//WovJFLa8EIGaziTVrc+XMAr81/ji2DQWqxoCuMKQRYeYPv 1GBx55Q+46QRiR/iWHkw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mTT6b-00CJKY-Ej; Thu, 23 Sep 2021 18:05:57 +0000 Received: from mail-vk1-f178.google.com ([209.85.221.178]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mTT6Y-00CJJn-Fr for linux-arm-kernel@lists.infradead.org; Thu, 23 Sep 2021 18:05:55 +0000 Received: by mail-vk1-f178.google.com with SMTP id s137so2931895vke.11 for ; Thu, 23 Sep 2021 11:05:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=rBW9oigA3M6I4upMBiJaZfcaxJFLLXlzf1RS4A+4bEM=; b=eu7klWn4WBsUTw84UrVz3ugb+KJXhwsthAJJrH/EDsaFlvorM1mee0n2naBd62ABeU 3tPmBX1H4OD6pYWMVfiCdvbp4PZptWgdXH0MADAmL4VDZRK8UL1JDDrBRvSJRdzw6OMz SYKejUozIvUxxx4qu3cvTk7TYnPam1OF1E1y7PJOILdh1S+NpQehvqGDjGsqSUo1VnSy anL5CBfoAIm35yNtkJ1VcPPelctMFXNc07Yn4ZPQ/mYKM9xx0YpQcY684cMfRlB7o575 F4APqTVFmvm9oNsLKYhH4bo7SKBHoyxwyZagtb8K0pSOAtpYx0w48BqUk7sJOa7gKe9K qpHQ== X-Gm-Message-State: AOAM5313Vv9uG1j13m95O5drXqWSBRMqN2cd52ZocOhJ70O4p0SLg4pM xTpf1Tv25gt+JS+Ozx8hfayAEP10ZdmG9ukhNn4= X-Google-Smtp-Source: ABdhPJz4AjvCw8fTJexqs6DkYP0oJBEeFwh+VuYL7GrwofLh9foa4aAVcIhkOm69AWOZpHSirP8hK3g44fRmA8vVrlY= X-Received: by 2002:a1f:9187:: with SMTP id t129mr4910403vkd.15.1632420352877; Thu, 23 Sep 2021 11:05:52 -0700 (PDT) MIME-Version: 1.0 References: <20210920190350.3860821-1-willmcvicker@google.com> <20210920190350.3860821-3-willmcvicker@google.com> <2b48a41a-9130-b4cc-40d3-0bc7930ac76a@canonical.com> In-Reply-To: From: Geert Uytterhoeven Date: Thu, 23 Sep 2021 20:05:41 +0200 Message-ID: Subject: Re: [PATCH v1 2/4] soc: samsung: change SOC_SAMSUNG default config logic To: Lee Jones Cc: Krzysztof Kozlowski , Will McVicker , Catalin Marinas , Will Deacon , "Cc: Android Kernel" , Linux ARM , Linux Kernel Mailing List , linux-samsung-soc , Greg KH X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210923_110554_572079_538EBBDF X-CRM114-Status: GOOD ( 34.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Sep 23, 2021 at 6:19 PM Geert Uytterhoeven wrote: > On Thu, Sep 23, 2021 at 3:42 PM Lee Jones wrote: > > On Thu, 23 Sep 2021, Krzysztof Kozlowski wrote: > > > On 23/09/2021 14:39, Lee Jones wrote: > > > > As I've explained before, the trigger for all of this was > > > > SERIAL_SAMSUNG which is required for early console on supported > > > > Samsung platforms i.e. this symbol *has* to be built-in. > > > > > > Actually SERIAL_SAMSUNG does not have to be built-in. It is necessary > > > for built-in only for debugging or development, not for real products. > > > > Right. And in the early stages, GKI is used for early (non-released) > > H/W (this is also the part of the reason these differences can't be > > upstreamed early/now/yet) and sometimes changes break things requiring > > low-level debugging techniques to solve (inc. early console). > > > > > Unlike other drivers which have to be built-in, e.g. clocks or pinctrl, > > > or heavily tested whether setup from initrd works. Plus not breaking > > > distros who like to have everything as module (solution from Geert?)... > > > > We don't know which drivers *need* to be built-in yet. > > > > Clocks is probably not a good example even, since the power-on default > > is most likely all-on, which is fine. Pinctrl remains to be seen. > > Clocks is an excellent example: if a clock is missing, the driver > will fail to probe (unless the clock is considered optional by > the driver), regardless of the power-on or boot loader defaults. > With fw_devlinks=on (which is the default now, and developed by a > Google engineer (GKI or another division?)), the driver won't even > get to the probing point. > > Pinctrl is different, as unless I'm mistaken, drivers will still > probe if the pin control driver is missing, so they will work if the > power-on or boot loader defaults of pin control are fine. In addition, relying on implicit power-on or boot loader state comes with its own set of pitfalls, which may break other use cases. On a heavily power-managed mobile device, clocks and/or power domains can be turned off, so a kernel launched from kexec or kdump may start in a state not adhering to these implicit dependencies. 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel