linux-kernel - Re: [PATCH v2 6/9] ASoC: tegra: add Tegra186 based DSPK driver

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Date:   Mon, 10 Feb 2020 20:19:09 +0530
From:   Sameer Pujar <spujar@...dia.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Dmitry Osipenko <digetx@...il.com>
CC:     <spujar@...dia.com>, <perex@...ex.cz>, <tiwai@...e.com>,
        <robh+dt@...nel.org>, <broonie@...nel.org>, <lgirdwood@...il.com>,
        <thierry.reding@...il.com>, <alsa-devel@...a-project.org>,
        <devicetree@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <sharadg@...dia.com>,
        <mkumard@...dia.com>, <viswanathl@...dia.com>,
        <rlokhande@...dia.com>, <dramesh@...dia.com>,
        <atalambedu@...dia.com>
Subject: Re: [PATCH v2 6/9] ASoC: tegra: add Tegra186 based DSPK driver



On 2/10/2020 5:52 PM, Jon Hunter wrote:
> On 10/02/2020 11:15, Sameer Pujar wrote:
>>
>> On 2/7/2020 11:52 PM, Dmitry Osipenko wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> 07.02.2020 14:26, Sameer Pujar пишет:
>>>> On 2/6/2020 10:45 PM, Dmitry Osipenko wrote:
>>>>> External email: Use caution opening links or attachments
>>>>>
>>>>>
>>>>> 30.01.2020 13:33, Sameer Pujar пишет:
>>>>>> +static const struct dev_pm_ops tegra186_dspk_pm_ops = {
>>>>>> +     SET_RUNTIME_PM_OPS(tegra186_dspk_runtime_suspend,
>>>>>> +                        tegra186_dspk_runtime_resume, NULL)
>>>>>> +     SET_LATE_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
>>>>>> +                                  pm_runtime_force_resume)
>>>>>> +};
>>>>> Could you please explain why drivers need the "late" system sleep?
>>>> It was done to ensure core drivers are suspended first and defer the
>>>> codec driver suspend
>>> Suspend order is opposite to the drivers registration order. If there is
>>> no real problem with that, then you should use the default suspend
>>> level. Please don't try to fix a non-existent problems.
>> No. This was done specifically to allow sound core to first stop any
>> ongoing audio activity during normal suspend and ensure a safe suspend
>> of AHUB devices by doing a LATE suspend.
> What Dmitry is saying is that if the DSPK driver is registered after the
> sound core then we will not need to suspend in the late phase. The DSPK
> device should only be registered once the sound core is loaded, because
> otherwise we should fail to register it with the sound core. So I don't
> think we need this to be late afterall.

I was originally thinking if DMA is the main reason for using LATE 
suspend for audio drivers as well. I did a small sanity check and 
appears normal suspend is fine. I will update the drivers with normal 
suspend. If we come across any issue later, it can be addressed 
separately. Thanks Dmitry and Jon.
>
> Jon
>