Messages in this thread | | | Subject | Re: [alsa-devel] [PATCH 4/9] ASoC: tegra: add Tegra210 based I2S driver | From | Sameer Pujar <> | Date | Thu, 23 Jan 2020 14:52:14 +0530 |
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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); >> Now for Tegra210 (or actually 64-bit Tegra) RPM is always enabled and so >> we don't need to worry about the !RPM case. However, I still don't see >> the harm in this. > There is no real harm today, but: > > 1. I'd prefer to be very careful with RPM in general, based on > previous experience. > > 2. It should be a bug if device isn't RPM-suspended during > of driver's removal. Thus the real problem needs to be fixed > rather than worked around.
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