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=-3.7 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 ED690C433E0 for ; Wed, 27 Jan 2021 17:01:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AA7B64DA1 for ; Wed, 27 Jan 2021 17:01:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231848AbhA0RA6 (ORCPT ); Wed, 27 Jan 2021 12:00:58 -0500 Received: from mail-oi1-f178.google.com ([209.85.167.178]:44814 "EHLO mail-oi1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234430AbhA0Q5V (ORCPT ); Wed, 27 Jan 2021 11:57:21 -0500 Received: by mail-oi1-f178.google.com with SMTP id n7so2825069oic.11; Wed, 27 Jan 2021 08:57:05 -0800 (PST) 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=s3xf6Uj3TbfKhQEJk82fq5fqzQLpVMzJXmRWZDS7dvk=; b=frcG7yHDg8zsAZ/HM42VeOkYgKdfQGDe8w9MCFZX8fDkftS6xkdk+1HOz6qErJmz66 xlmFUzkrtFL4CIbBDSvSy6xakFns+H/sG/X7lJeqZUcXaaYrtgRE/IsHrqAg7COSufZW pyGkKguSc2LpQIa9A5zDXddnH7/WLxBIaeB/AbDvr8ySH5LT3ka7einhC+rBFhc6hEzN gy6wguy1QENOtJ7JDgfqLhWf2Bf05SNaeXry+KCtIhac40ARaHcIX0QHYm3YjgrLsu4/ K5otYdIRsPWpqRIaKyhDGEbPDKqKpSu0I/YXILUvuo6BlwYXASn3JSRZ8C8sIxEVQYX3 kzrg== X-Gm-Message-State: AOAM530zWoG/V50mY0ffrGtvmj6Pgy/xMqTGA9v8jzUBjH9kgZA3uXHh S3ecxRiki7yaqTqM1QAsjHWugEkVEPY1I1Lzb98= X-Google-Smtp-Source: ABdhPJzrftirO9q8y5qRSTJjzPt8PKf7o5QMJ5YRZIls94zP1/ZFWbzW7vKZsZi8Q26ezhYy6mhE78Bj+1LTwsp+OYI= X-Received: by 2002:aca:4d8d:: with SMTP id a135mr3681544oib.153.1611766600227; Wed, 27 Jan 2021 08:56:40 -0800 (PST) MIME-Version: 1.0 References: <20210120105246.23218-1-michael@walle.cc> In-Reply-To: From: Geert Uytterhoeven Date: Wed, 27 Jan 2021 17:56:28 +0100 Message-ID: Subject: Re: [PATCH] PCI: dwc: layerscape: convert to builtin_platform_driver() To: Saravana Kannan Cc: Michael Walle , Lorenzo Pieralisi , Roy Zang , PCI , LKML , Minghuan Lian , Mingkai Hu , Greg Kroah-Hartman , Bjorn Helgaas , linuxppc-dev , linux-arm-kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Hi Saravana, On Wed, Jan 27, 2021 at 5:42 PM Saravana Kannan wrote: > On Tue, Jan 26, 2021 at 11:43 PM Geert Uytterhoeven > wrote: > > On Wed, Jan 27, 2021 at 1:44 AM Saravana Kannan wrote: > > > On Tue, Jan 26, 2021 at 12:50 AM Geert Uytterhoeven > > > wrote: > > > > On Mon, Jan 25, 2021 at 11:42 PM Saravana Kannan wrote: > > > > > On Mon, Jan 25, 2021 at 11:49 AM Michael Walle wrote: > > > > > > Am 2021-01-21 12:01, schrieb Geert Uytterhoeven: > > > > > > > On Thu, Jan 21, 2021 at 1:05 AM Saravana Kannan > > > > > > > wrote: > > > > > > >> On Wed, Jan 20, 2021 at 3:53 PM Michael Walle > > > > > > >> wrote: > > > > > > >> > Am 2021-01-20 20:47, schrieb Saravana Kannan: > > > > > > >> > > On Wed, Jan 20, 2021 at 11:28 AM Michael Walle > > > > > > >> > > wrote: > > > > > > >> > >> > > > > > > >> > >> [RESEND, fat-fingered the buttons of my mail client and converted > > > > > > >> > >> all CCs to BCCs :(] > > > > > > >> > >> > > > > > > >> > >> Am 2021-01-20 20:02, schrieb Saravana Kannan: > > > > > > >> > >> > On Wed, Jan 20, 2021 at 6:24 AM Rob Herring wrote: > > > > > > >> > >> >> > > > > > > >> > >> >> On Wed, Jan 20, 2021 at 4:53 AM Michael Walle > > > > > > >> > >> >> wrote: > > > > > > >> > >> >> > > > > > > > >> > >> >> > fw_devlink will defer the probe until all suppliers are ready. We can't > > > > > > >> > >> >> > use builtin_platform_driver_probe() because it doesn't retry after probe > > > > > > >> > >> >> > deferral. Convert it to builtin_platform_driver(). > > > > > > >> > >> >> > > > > > > >> > >> >> If builtin_platform_driver_probe() doesn't work with fw_devlink, then > > > > > > >> > >> >> shouldn't it be fixed or removed? > > > > > > >> > >> > > > > > > > >> > >> > I was actually thinking about this too. The problem with fixing > > > > > > >> > >> > builtin_platform_driver_probe() to behave like > > > > > > >> > >> > builtin_platform_driver() is that these probe functions could be > > > > > > >> > >> > marked with __init. But there are also only 20 instances of > > > > > > >> > >> > builtin_platform_driver_probe() in the kernel: > > > > > > >> > >> > $ git grep ^builtin_platform_driver_probe | wc -l > > > > > > >> > >> > 20 > > > > > > >> > >> > > > > > > > >> > >> > So it might be easier to just fix them to not use > > > > > > >> > >> > builtin_platform_driver_probe(). > > > > > > >> > >> > > > > > > > >> > >> > Michael, > > > > > > >> > >> > > > > > > > >> > >> > Any chance you'd be willing to help me by converting all these to > > > > > > >> > >> > builtin_platform_driver() and delete builtin_platform_driver_probe()? > > > > > > >> > >> > > > > > > >> > >> If it just moving the probe function to the _driver struct and > > > > > > >> > >> remove the __init annotations. I could look into that. > > > > > > >> > > > > > > > > >> > > Yup. That's pretty much it AFAICT. > > > > > > >> > > > > > > > > >> > > builtin_platform_driver_probe() also makes sure the driver doesn't ask > > > > > > >> > > for async probe, etc. But I doubt anyone is actually setting async > > > > > > >> > > flags and still using builtin_platform_driver_probe(). > > > > > > >> > > > > > > > >> > Hasn't module_platform_driver_probe() the same problem? And there > > > > > > >> > are ~80 drivers which uses that. > > > > > > >> > > > > > > >> Yeah. The biggest problem with all of these is the __init markers. > > > > > > >> Maybe some familiar with coccinelle can help? > > > > > > > > > > > > > > And dropping them will increase memory usage. > > > > > > > > > > > > Although I do have the changes for the builtin_platform_driver_probe() > > > > > > ready, I don't think it makes much sense to send these unless we agree > > > > > > on the increased memory footprint. While there are just a few > > > > > > builtin_platform_driver_probe() and memory increase _might_ be > > > > > > negligible, there are many more module_platform_driver_probe(). > > > > > > > > > > While it's good to drop code that'll not be used past kernel init, the > > > > > module_platform_driver_probe() is going even more extreme. It doesn't > > > > > even allow deferred probe (well before kernel init is done). I don't > > > > > think that behavior is right and that's why we should delete it. Also, > > > > > > > > This construct is typically used for builtin hardware for which the > > > > dependencies are registered very early, and thus known to probe at > > > > first try (if present). > > > > > > > > > I doubt if any of these probe functions even take up 4KB of memory. > > > > > > > > How many 4 KiB pages do you have in a system with 10 MiB of SRAM? > > > > How many can you afford to waste? > > > > > > There are only a few instances of this macro in the kernel. How many > > > > $ git grep -lw builtin_platform_driver_probe | wc -l > > 21 > > $ git grep -lw module_platform_driver_probe | wc -l > > 86 > > > > + the ones that haven't been converted to the above yet: > > > > $ git grep -lw platform_driver_probe | wc -l > > 58 > > > > Yeah, this adds up in terms of the number of places we'd need to fix. > But thinking more about it, a couple of points: > 1. Not all builtin_platform_driver_probe() are problems for > fw_devlink. So we can just fix them as we go if we need to. > > 2. The problem with builtin_platform_driver_probe() isn't really with > the use of __init. It's the fact that it doesn't allow deferred > probes. builtin_platform_driver_probe()/platform_driver_probe() could > still be fixed up to allow deferred probe until we get to the point > where we free the __init section (so at least till late_initcall). That's intentional: it is used for cases that will (must) never be deferred. That's why it's safe to use __init. 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