From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.manjaro.org (mail.manjaro.org [116.203.91.91]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 933EC1FBB; Wed, 26 Jun 2024 06:49:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=116.203.91.91 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719384562; cv=none; b=WWHv+mfYVw4xEasIBnVKyTGQGlIcixJ05Y5+HuR9CzVQeFogQRKHgSB4CUr4OQSRkCsefoHPIKFWl8ji3rvTT4RHjuxAET2cZsl7LcErD0K/Jyvtd957gy0RdDtjdtvUbJUg8OLiEezLc6BXPGb86+620c8YBcu9fqZtmMVBG1E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719384562; c=relaxed/simple; bh=biDrjTVnXctPMnU20CaOYokxJV4SVN9aMiUtJ9IAZgM=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=Xq8Fx8YH8W0JycP76SpH1RXj3aXWIWyHe+NAB4azp9vT/9T42K49dfgiZBi2YQEzbDyw3Yh6FT5pYM156caKCpUUy29XDHoRZUMFlwtOfYxq4c3ITTo/DLOQm6VF7uBZqf7a7LZdHUOTL50PKHGhjbuc5Tr1OszlSNF2yva0OU0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=manjaro.org; spf=pass smtp.mailfrom=manjaro.org; dkim=pass (2048-bit key) header.d=manjaro.org header.i=@manjaro.org header.b=flalXVv5; arc=none smtp.client-ip=116.203.91.91 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=manjaro.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=manjaro.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=manjaro.org header.i=@manjaro.org header.b="flalXVv5" Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=manjaro.org; s=2021; t=1719384551; 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=3EUy8ZqVg1I+dfYk8clcNPqBEg+z81Pl82YdSn3QsHY=; b=flalXVv5TjKTXtzblY1sXqL600OglvFnNH6rPY7PA8Y4xq3XyESFI2EqKeIaBSjlV0/RwC l2HbYfUjwWtnBlpp4MX7Ca+4KrD3i2oK5Crm0VkoiPXb36uBkL32FheSm9tss2hP3+Kx1b kH9N5PByLsIm9YwCZW65l93mwSf4koSoRTaXKiTgEgovZ5GRdOT3UUeByAzDMobPMIw99I BNKnofU2wzizYJLyQ7Wsltar/uxrjg23ML/cEVg28ZQjjbkECgqsw1YSnlkb7Wkn2/FYLw VMVJNRzMJl9MWz3+pPEMqTiWU3PsHzLrj3NVTOmK1WBeEVQahl+OsO7/9lh9dg== Date: Wed, 26 Jun 2024 08:49:09 +0200 From: Dragan Simic To: Qiang Yu Cc: Maxime Ripard , dri-devel@lists.freedesktop.org, lima@lists.freedesktop.org, maarten.lankhorst@linux.intel.com, tzimmermann@suse.de, airlied@gmail.com, daniel@ffwll.ch, linux-kernel@vger.kernel.org, Philip Muller , Oliver Smith , Daniel Smith , stable@vger.kernel.org Subject: Re: [PATCH] drm/lima: Mark simple_ondemand governor as softdep In-Reply-To: References: <20240618-great-hissing-skink-b7950e@houat> <4813a6885648e5368028cd822e8b2381@manjaro.org> <457ae7654dba38fcd8b50e38a1275461@manjaro.org> <2c072cc4bc800a0c52518fa2476ef9dd@manjaro.org> Message-ID: <74c69c3bb4498099a195ec890e1a7896@manjaro.org> X-Sender: dsimic@manjaro.org Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Authentication-Results: ORIGINATING; auth=pass smtp.auth=dsimic@manjaro.org smtp.mailfrom=dsimic@manjaro.org Hello Qiang, On 2024-06-26 03:11, Qiang Yu wrote: > On Wed, Jun 26, 2024 at 2:15 AM Dragan Simic > wrote: >> >> Hello everyone, >> >> Just checking, any further thoughts about this patch? >> > I'm OK with this as a temp workaround because it's simple and do no > harm > even it's not perfect. If no other better suggestion for short term, > I'll submit > this at weekend. Thanks. Just as you described it, it's far from perfect, but it's still fine until there's a better solution, such as harddeps. I'll continue my research about the possibility for adding harddeps, which would hopefully replace quite a few instances of the softdep (ab)use. >> On 2024-06-18 21:22, Dragan Simic wrote: >> > On 2024-06-18 12:33, Dragan Simic wrote: >> >> On 2024-06-18 10:13, Maxime Ripard wrote: >> >>> On Tue, Jun 18, 2024 at 04:01:26PM GMT, Qiang Yu wrote: >> >>>> On Tue, Jun 18, 2024 at 12:33 PM Qiang Yu wrote: >> >>>> > >> >>>> > I see the problem that initramfs need to build a module dependency chain, >> >>>> > but lima does not call any symbol from simpleondemand governor module. >> >>>> > softdep module seems to be optional while our dependency is hard one, >> >>>> > can we just add MODULE_INFO(depends, _depends), or create a new >> >>>> > macro called MODULE_DEPENDS()? >> >> >> >> I had the same thoughts, because softdeps are for optional module >> >> dependencies, while in this case it's a hard dependency. Though, >> >> I went with adding a softdep, simply because I saw no better option >> >> available. >> >> >> >>>> This doesn't work on my side because depmod generates modules.dep >> >>>> by symbol lookup instead of modinfo section. So softdep may be our >> >>>> only >> >>>> choice to add module dependency manually. I can accept the softdep >> >>>> first, then make PM optional later. >> >> >> >> I also thought about making devfreq optional in the Lima driver, >> >> which would make this additional softdep much more appropriate. >> >> Though, I'm not really sure that's a good approach, because not >> >> having working devfreq for Lima might actually cause issues on >> >> some devices, such as increased power consumption. >> >> >> >> In other words, it might be better to have Lima probing fail if >> >> devfreq can't be initialized, rather than having probing succeed >> >> with no working devfreq. Basically, failed probing is obvious, >> >> while a warning in the kernel log about no devfreq might easily >> >> be overlooked, causing regressions on some devices. >> >> >> >>> It's still super fragile, and depends on the user not changing the >> >>> policy. It should be solved in some other, more robust way. >> >> >> >> I see, but I'm not really sure how to make it more robust? In >> >> the end, some user can blacklist the simple_ondemand governor >> >> module, and we can't do much about it. >> >> >> >> Introducing harddeps alongside softdeps would make sense from >> >> the design standpoint, but the amount of required changes wouldn't >> >> be trivial at all, on various levels. >> > >> > After further investigation, it seems that the softdeps have >> > already seen a fair amount of abuse for what they actually aren't >> > intended, i.e. resolving hard dependencies. For example, have >> > a look at the commit d5178578bcd4 (btrfs: directly call into >> > crypto framework for checksumming) [1] and the lines containing >> > MODULE_SOFTDEP() at the very end of fs/btrfs/super.c. [2] >> > >> > If a filesystem driver can rely on the abuse of softdeps, which >> > admittedly are a bit fragile, I think we can follow the same >> > approach, at least for now. >> > >> > With all that in mind, I think that accepting this patch, as well >> > as the related Panfrost patch, [3] should be warranted. I'd keep >> > investigating the possibility of introducing harddeps in form >> > of MODULE_HARDDEP() and the related support in kmod project, >> > similar to the already existing softdep support, [4] but that >> > will inevitably take a lot of time, both for implementing it >> > and for reaching various Linux distributions, which is another >> > reason why accepting these patches seems reasonable. >> > >> > [1] >> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d5178578bcd4 >> > [2] >> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/btrfs/super.c#n2593 >> > [3] >> > https://lore.kernel.org/dri-devel/4e1e00422a14db4e2a80870afb704405da16fd1b.1718655077.git.dsimic@manjaro.org/ >> > [4] >> > https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/commit/?id=49d8e0b59052999de577ab732b719cfbeb89504d