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[79.139.233.37]) by smtp.googlemail.com with ESMTPSA id r10sm484836ljk.99.2020.01.23.07.16.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jan 2020 07:16:02 -0800 (PST) Subject: Re: [alsa-devel] [PATCH 4/9] ASoC: tegra: add Tegra210 based I2S driver To: Sameer Pujar , Jon Hunter Cc: perex@perex.cz, tiwai@suse.com, robh+dt@kernel.org, devicetree@vger.kernel.org, alsa-devel@alsa-project.org, atalambedu@nvidia.com, linux-kernel@vger.kernel.org, lgirdwood@gmail.com, viswanathl@nvidia.com, sharadg@nvidia.com, broonie@kernel.org, thierry.reding@gmail.com, linux-tegra@vger.kernel.org, rlokhande@nvidia.com, mkumard@nvidia.com, dramesh@nvidia.com References: <1579530198-13431-1-git-send-email-spujar@nvidia.com> <1579530198-13431-5-git-send-email-spujar@nvidia.com> <0c571858-d72c-97c2-2d6a-ead6fdde06eb@nvidia.com> <444731da-c4cd-8578-a732-c803eef31ef0@gmail.com> <598fe377-5b95-d30a-eb64-89a645166d42@gmail.com> <3f51939d-cf4b-f69b-728a-7eb99bbae458@nvidia.com> <34ac1fd3-ae0f-07f2-555f-a55087a2c9dc@nvidia.com> <1a84b393-938f-8bed-d08e-cc3bb6ed4844@gmail.com> <0fc814c2-0dc6-7741-b954-463381ff7fb9@nvidia.com> From: Dmitry Osipenko Message-ID: Date: Thu, 23 Jan 2020 18:16:01 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <0fc814c2-0dc6-7741-b954-463381ff7fb9@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 23.01.2020 12:22, Sameer Pujar пишет: > > > On 1/22/2020 9:57 PM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 22.01.2020 14:52, Jon Hunter пишет: >>> On 22/01/2020 07:16, Sameer Pujar wrote: >>> >>> ... >>> >>>>>>>>>> +static int tegra210_i2s_remove(struct platform_device *pdev) >>>>>>>>>> +{ >>>>>>>>>> +     pm_runtime_disable(&pdev->dev); >>>>>>>>>> +     if (!pm_runtime_status_suspended(&pdev->dev)) >>>>>>>>>> +             tegra210_i2s_runtime_suspend(&pdev->dev); >>>>>>>>> This breaks device's RPM refcounting if it was disabled in the >>>>>>>>> active >>>>>>>>> state. This code should be removed. At most you could warn >>>>>>>>> about the >>>>>>>>> unxpected RPM state here, but it shouldn't be necessary. >>>>>>>> I guess this was added for safety and explicit suspend keeps clock >>>>>>>> disabled. >>>>>>>> Not sure if ref-counting of the device matters when runtime PM is >>>>>>>> disabled and device is removed. >>>>>>>> I see few drivers using this way. >>>>>>> It should matter (if I'm not missing something) because RPM should >>>>>>> be in >>>>>>> a wrecked state once you'll try to re-load the driver's module. >>>>>>> Likely >>>>>>> that those few other drivers are wrong. >>>>>>> >>>>>>> [snip] >>>>>> Once the driver is re-loaded and RPM is enabled, I don't think it >>>>>> would use >>>>>> the same 'dev' and the corresponding ref count. Doesn't it use the >>>>>> new >>>>>> counters? >>>>>> If RPM is not working for some reason, most likely it would be the >>>>>> case >>>>>> for other >>>>>> devices. What best driver can do is probably do a force suspend >>>>>> during >>>>>> removal if >>>>>> already not done. I would prefer to keep, since multiple drivers >>>>>> still >>>>>> have it, >>>>>> unless there is a real harm in doing so. >>>>> I took a closer look and looks like the counter actually should be >>>>> reset. Still I don't think that it's a good practice to make changes >>>>> underneath of RPM, it may strike back. >>>> If RPM is broken, it probably would have been caught during device >>>> usage. >>>> I will remove explicit suspend here if no any concerns from other >>>> folks. >>>> Thanks. >>> I recall that this was the preferred way of doing this from the RPM >>> folks. Tegra30 I2S driver does the same and Stephen had pointed me to >>> this as a reference. >>> I believe that this is meant to ensure that the >>> device is always powered-off regardless of it RPM is enabled or not and >>> what the current state is. >> Yes, it was kinda actual for the case of unavailable RPM. > >> Anyways, /I think/ variant like this should have been more preferred: >> >> if (!pm_runtime_enabled(&pdev->dev)) >>          tegra210_i2s_runtime_suspend(&pdev->dev); >> else >>          pm_runtime_disable(&pdev->dev); > > I think it looks to be similar to what is there already. > > pm_runtime_disable(&pdev->dev); // it would turn out to be a dummy call > if !RPM > if (!pm_runtime_status_suspended(&pdev->dev)) // it is true always if !RPM >         tegra210_i2s_runtime_suspend(&pdev->dev); Maybe this is fine for !RPM, but not really fine in a case of enabled RPM. Device could be in resumed state after pm_runtime_disable() if it wasn't suspended before the disabling.