From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9AAA528F1; Fri, 19 Apr 2024 18:45:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713552322; cv=none; b=hxxqgmz0of6bgachtlJMNWo+3QInMBDe73I0DJVR4uDffQG14bIhoWbMCTPVH6p9dj3FcmelTnPoOQ9BXbLru4XZkSQnH7aBhjJ2ZNPJrVDV5+sqdJTrmaOAhXm99uV6U/aCMmPDG9/7VHXvO8SgH67/KPvi6MXsRJDpN98Sspg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713552322; c=relaxed/simple; bh=kH9eAX2qPCNtZOepbYbfhtqMFcfcuJTqLUEMbRtXRMU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LsUjmfA51NMokOZLXtv6EbS91XesuX1j8WA4UJXFXIDswY4ydlsnHOZZvE0V5aDZhIyrMhjL99gPaXe/CviMzd15ne4UbiJM32YrD7JFFYuppoWSb52DNpCG9hqNFi0NJZu9Ca1LnrRGSLWZLq7xkR0AJ6W1gEqrWPHrpMM/SAI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iZMLYLA5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iZMLYLA5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EA33AC072AA; Fri, 19 Apr 2024 18:45:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713552322; bh=kH9eAX2qPCNtZOepbYbfhtqMFcfcuJTqLUEMbRtXRMU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iZMLYLA53ZTZVEjGnEVwQ6u1OFkPakSVPeAocIW5W/f5JUQp22kiiG7oq122pZ3EH Va9LyNSqUhumkDqOy4BYQZhFiGGEStCu8cjMiFt6hHsaYLf+rCRKKCpjY6g7OtvizN HSogEYLRCpZ/J+XgvFL2/NOfVQpP1Oqj/jm1IwzHJqKzvjQGyvXFuFPWcb3D8uhXD2 Hg/UBYROGg7x+aED0AQO9zI8xZ2SKs23RxlnDWXJiayWSvOf+rhQlk/HVIwzCRTwRG PLDUJxJKXSqWRp3aYhTpo53bVow3X9oJPMGZ2ENaBtJmU/WGWqVW4zCbKNZvIkRhzv Vj1kjgviLNIHA== Message-ID: Date: Fri, 19 Apr 2024 20:45:21 +0200 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 5/6] soc: qcom: add pd-mapper implementation To: Dmitry Baryshkov Cc: Bjorn Andersson , Konrad Dybcio , Mathieu Poirier , Sibi Sankar , Bartosz Golaszewski , linux-arm-msm@vger.kernel.org, linux-remoteproc@vger.kernel.org, Johan Hovold , Xilin Wu References: <20240419-qcom-pd-mapper-v5-0-e35b6f847e99@linaro.org> <20240419-qcom-pd-mapper-v5-5-e35b6f847e99@linaro.org> <67c90fcd-df2f-40e4-9507-dcc9340f2319@kernel.org> Content-Language: en-US From: Krzysztof Kozlowski Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 19/04/2024 20:24, Dmitry Baryshkov wrote: >>>>> +}; >>>> >>>> If this is supposed to be a module, then why no MODULE_DEVICE_TABLE? >>> >>> Ok, I should add this to the commit message. >>> >>> For now: >>> >>> This module is loaded automatically by the remoteproc drivers when >> >> Hm? How remoteproc loads this module? > > remoteproc drivers call qcom_pdm_start(). This brings in this module > via symbol deps. Ah, right, I understand now. So this should not be loaded on its own on the machine. > >> >>> necessary. It uses a root node to match a protection domains map for a >>> particular device. >>> >>>> >>>>> + >>>>> +static int qcom_pdm_start(void) >>>>> +{ >>>>> + const struct of_device_id *match; >>>>> + const struct qcom_pdm_domain_data * const *domains; >>>>> + struct device_node *root; >>>>> + int ret, i; >>>>> + >>>>> + pr_debug("PDM: starting service\n"); >>>> >>>> Drop simple entry/exit debug messages. >>> >>> ack >>> >>>> >>>>> + >>>>> + root = of_find_node_by_path("/"); >>>>> + if (!root) >>>>> + return -ENODEV; >>>>> + >>>>> + match = of_match_node(qcom_pdm_domains, root); >>>>> + of_node_put(root); >>>>> + if (!match) { >>>>> + pr_notice("PDM: no support for the platform, userspace daemon might be required.\n"); >>>>> + return 0; >>>>> + } >>>>> + >>>>> + domains = match->data; >>>> >>>> All this is odd a bit. Why is this not a driver? You are open coding >>>> here of_device_get_match_data(). >>> >>> Except that it matches the root node instead of matching a device. >> >> Yep, but if this was proper device then things get simpler, don't they? > > I don't think we are supposed to have devices for software things? > This is purely a software construct. It replaces userspace daemon for > the reason outlined in the cover letter, but other than that there is > no hardware entity. Not even a firmware entity to drive this thing. Firmware interfaces are also not "devices" but we create device drivers for them. The code lies in drivers, so it is a driver, even if somehow kernel software construct. fs/pstore/ram also has a driver, even though this is software device to handle ram dumps (it is not a driver for RAM). net/qrtr/smd.c is not even in the drivers and as well describes some sort of software daemon. If this was not a driver, then it would be a subsystem... but it is not a subsystem, right? > >>>>> + >>>>> + if (!ret) >>>>> + ++qcom_pdm_count; >>>>> + >>>>> + mutex_unlock(&qcom_pdm_mutex); >>>> >>>> Looks like you implement refcnt manually... >>> >>> Yes... There is refcount_dec_and_mutex_lock(), but I found no >>> corresponding refcount_add_and_mutex_lock(). Maybe I'm >>> misunderstanding that framework. >>> I need to have a mutex after incrementing the lock from 0, so that the >>> driver can init QMI handlers. >>> >>>> Also, what happens if this module gets unloaded? How do you handle >>>> module dependencies? I don't see any device links. Bartosz won't be >>>> happy... We really need to stop adding more of >>>> old-style-buggy-never-unload-logic. At least for new code. >>> >>> Module dependencies are handled by the symbol dependencies. >> >> You mean build dependencies, not runtime load. > > No, I mean runtime load dependencies. > >> >>> Remoteproc module depends on this symbol. Once q6v5 remoteproc modules >>> are unloaded this module can be unloaded too. >> >> I am pretty sure you can unload this and get crashes. > > If for some reason somebody has called qcom_pdm_get() without > qcom_pdm_release(), then yes. To make it 100% safe, I can cleanup > actions to module_exit(), but for me it looks like an overkill. I'll come with some more concrete example if you are not convinced. Best regards, Krzysztof