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From: Jon Hunter <jonathanh@nvidia.com>
To: "Dmitry Osipenko" <digetx@gmail.com>,
	"Laxman Dewangan" <ldewangan@nvidia.com>,
	"Vinod Koul" <vkoul@kernel.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: <dmaengine@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 12/16] dmaengine: tegra-apb: Clean up suspend-resume
Date: Thu, 30 Jan 2020 18:58:37 +0000	[thread overview]
Message-ID: <08b6a1f7-3c4d-ce6a-0d00-450f7bd4eeb3@nvidia.com> (raw)
In-Reply-To: <3d8f599d-a46f-a7e5-8816-e0c44e2aceff@gmail.com>


On 30/01/2020 18:26, Dmitry Osipenko wrote:
> 30.01.2020 21:06, Dmitry Osipenko пишет:
>> 30.01.2020 19:08, Dmitry Osipenko пишет:
>>> 30.01.2020 17:09, Jon Hunter пишет:
>>>>
>>>> On 30/01/2020 04:38, Dmitry Osipenko wrote:
>>>>> It is enough to check whether hardware is busy on suspend and to reset
>>>>> it across of suspend-resume because channel's configuration is fully
>>>>> re-programmed on each DMA transaction anyways and because save-restore
>>>>> of an active channel won't end up well without pausing transfer prior to
>>>>> saving of the state (note that all channels shall be idling at the time of
>>>>> suspend, so save-restore is not needed at all).
>>>>
>>>> I guess if we ever wanted to support SNDRV_PCM_INFO_PAUSE for audio and
>>>> support the pause callback, then saving and restoring the channels could
>>>> be needed. Right now I believe that it will just terminate_all transfers
>>>> for audio on entering suspend. Any value in keeping this?
>>>
>>> Indeed, looks like [1] pauses DMA during suspend if SNDRV_PCM_INFO_PAUSE
>>> is supported.
>>>
>>> [1]
>>> https://elixir.bootlin.com/linux/v5.5/source/sound/core/pcm_dmaengine.c#L199
>>>
>>> So we'll need to save-restore context only if DMA is in a paused state
>>> during suspend, I'll adjust this patch to do that and will see if
>>> enabling SNDRV_PCM_INFO_PAUSE works.
>>
>> I started to look at it and found that the .device_pause() hook isn't
>> implemented by the driver. So, it's fine to remove the context's
>> save-restore for now.
>>
>> Jon, what about to keep this patch as-is? Later on I'll take a look at
>> implementing the proper pausing functionality and try to cleanup code a
>> bit further (remove the free list usage, etc).
> 
> Ah, only T114+ supports the per-channel pausing. So, I won't care about
> implementing the device_pause(), let's leave it to somebody else :)

That's fine. We have lived with out it for this long.

Jon

-- 
nvpublic

  reply	other threads:[~2020-01-30 18:58 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-30  4:37 [PATCH v6 00/16] NVIDIA Tegra APB DMA driver fixes and improvements Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 01/16] dmaengine: tegra-apb: Fix use-after-free Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 02/16] dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 03/16] dmaengine: tegra-apb: Implement synchronization hook Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 04/16] dmaengine: tegra-apb: Prevent race conditions on channel's freeing Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 05/16] dmaengine: tegra-apb: Clean up tasklet releasing Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 06/16] dmaengine: tegra-apb: Use devm_platform_ioremap_resource Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 07/16] dmaengine: tegra-apb: Use devm_request_irq Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 08/16] dmaengine: tegra-apb: Fix coding style problems Dmitry Osipenko
2020-01-30 14:08   ` Jon Hunter
2020-01-30  4:37 ` [PATCH v6 09/16] dmaengine: tegra-apb: Remove unneeded initialization of tdc->config_init Dmitry Osipenko
2020-01-30 14:08   ` Jon Hunter
2020-01-30  4:37 ` [PATCH v6 10/16] dmaengine: tegra-apb: Remove assumptions about unavailable runtime PM Dmitry Osipenko
2020-01-30 14:09   ` Jon Hunter
2020-01-30 16:09     ` Dmitry Osipenko
2020-01-30  4:37 ` [PATCH v6 11/16] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer Dmitry Osipenko
2020-01-30 14:09   ` Jon Hunter
2020-01-30 16:11     ` Dmitry Osipenko
2020-01-30 18:45       ` Jon Hunter
2020-01-30 20:04         ` Dmitry Osipenko
2020-01-31  9:02           ` Jon Hunter
2020-01-31 14:22             ` Dmitry Osipenko
2020-02-01 15:13               ` Dmitry Osipenko
2020-02-03 11:37                 ` Jon Hunter
2020-02-03 16:24                   ` Dmitry Osipenko
2020-01-31  9:05   ` Jon Hunter
2020-01-30  4:38 ` [PATCH v6 12/16] dmaengine: tegra-apb: Clean up suspend-resume Dmitry Osipenko
2020-01-30 14:09   ` Jon Hunter
2020-01-30 16:08     ` Dmitry Osipenko
2020-01-30 18:06       ` Dmitry Osipenko
2020-01-30 18:26         ` Dmitry Osipenko
2020-01-30 18:58           ` Jon Hunter [this message]
2020-01-30 19:00   ` Jon Hunter
2020-01-30 20:06     ` Dmitry Osipenko
2020-01-30  4:38 ` [PATCH v6 13/16] dmaengine: tegra-apb: Add missing of_dma_controller_free Dmitry Osipenko
2020-01-30  4:38 ` [PATCH v6 14/16] dmaengine: tegra-apb: Allow to compile as a loadable kernel module Dmitry Osipenko
2020-01-30  4:38 ` [PATCH v6 15/16] dmaengine: tegra-apb: Remove MODULE_ALIAS Dmitry Osipenko
2020-01-30  4:38 ` [PATCH v6 16/16] dmaengine: tegra-apb: Support COMPILE_TEST Dmitry Osipenko
2020-01-30 14:10   ` Jon Hunter

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