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 6F3F413BC2F; Tue, 25 Jun 2024 18:15:33 +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=1719339337; cv=none; b=MFVYAisWVYg8ZJPjNTxNVrSBDmSXdbqpmeHL82xEy87Nbmnqb3C7dt1Gubj/WvMvXOna5Dxyj2+P8jovro9Jy7qhe7/7CFLHuXLNq7x1W1wsCbCB9Dem19ZF8HXMv0GWVfNE54saOTmNQeQmzyKddX/gkYHKaKjdzPf2vCpSrwc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719339337; c=relaxed/simple; bh=c1YPqLsd/PZZOqnbat83z7KOPHi+vCF4g7CQiVRUy2s=; h=MIME-Version:Date:From:To:Cc:Subject:In-Reply-To:References: Message-ID:Content-Type; b=cDHtsXjJVOvpA2suqjby11QoGRJfMuDoV/4skPDhSiL6M2jaR6F47NpSjXOhv1WwPm38VmMSxT0VL7BbA1FZPfqaLXnRsuNASwFS8Q2BTN4IB15wOpmBQWhQEUeqbnddB5+faDHmpRsfZ6S0w6pxVQmBLCwMezMRE1VcsPLrtR0= 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=loLhMqFG; 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="loLhMqFG" Precedence: bulk X-Mailing-List: linux-kernel@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=1719339330; 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=VgdNz8GhllyBAYDE79E5X5a/W0pTJU2nuZpZ5CuBm9Y=; b=loLhMqFGKS6bl+M010SntmQrppSMI3Xofn9x7rk8E4RTpUG3G6QLUbKDo48mpoDNs2RTPz jl0MaMoiitpE+nfPzUqVIsuf8u71zBE9Je21l5lXOX8uPeL53iilUWIUzrmg6V1ZvguS68 O0T9l1dPqQLy+38r79te0SQGprQz2rYQDVltW+312wy48MpH9MX9FwEZetjkIRKy2hKXmG xsjJQiYV/qmj8pfuIZXLphXSsBMYkScqjlzYRnHw4BMQ6Qh/Fq5CTJjOnxDa1ytqWy2SMW d5x5F5MfWuw20q7dkfv6oujwL6UoyfK0VkjsKFGAR2hqb3fr4EzihcDISc+HPw== Date: Tue, 25 Jun 2024 20:15:28 +0200 From: Dragan Simic To: Maxime Ripard Cc: Qiang Yu , 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: <457ae7654dba38fcd8b50e38a1275461@manjaro.org> References: <20240618-great-hissing-skink-b7950e@houat> <4813a6885648e5368028cd822e8b2381@manjaro.org> <457ae7654dba38fcd8b50e38a1275461@manjaro.org> Message-ID: <2c072cc4bc800a0c52518fa2476ef9dd@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 everyone, Just checking, any further thoughts about this patch? 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