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

From: Sameer Pujar <spujar@nvidia.com>
To: Jon Hunter <jonathanh@nvidia.com>, Dmitry Osipenko <digetx@gmail.com>
Cc: <spujar@nvidia.com>, <perex@perex.cz>, <tiwai@suse.com>,
	<robh+dt@kernel.org>, <broonie@kernel.org>, <lgirdwood@gmail.com>,
	<thierry.reding@gmail.com>, <alsa-devel@alsa-project.org>,
	<devicetree@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <sharadg@nvidia.com>,
	<mkumard@nvidia.com>, <viswanathl@nvidia.com>,
	<rlokhande@nvidia.com>, <dramesh@nvidia.com>,
	<atalambedu@nvidia.com>
Subject: Re: [PATCH v2 6/9] ASoC: tegra: add Tegra186 based DSPK driver
Date: Mon, 10 Feb 2020 20:19:09 +0530	[thread overview]
Message-ID: <ffff29e1-7ffb-01a0-a36a-fbc1e0604e5c@nvidia.com> (raw)
In-Reply-To: <4c75fc51-fbfd-158f-a096-d4f178921ee3@nvidia.com>


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
>