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From: Dmitry Osipenko <digetx@gmail.com>
To: "Jon Hunter" <jonathanh@nvidia.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 v3 09/13] dmaengine: tegra-apb: Remove runtime PM usage
Date: Tue, 7 Jan 2020 20:12:45 +0300	[thread overview]
Message-ID: <fd6215ac-a646-4e13-ee22-e815a69cd099@gmail.com> (raw)
In-Reply-To: <f63a68cf-bb9d-0e79-23f3-233fc97ca6f9@nvidia.com>

Hello Jon,

07.01.2020 18:13, Jon Hunter пишет:
> 
> On 06/01/2020 01:17, Dmitry Osipenko wrote:
>> There is no benefit from runtime PM usage for the APB DMA driver because
>> it enables clock at the time of channel's allocation and thus clock stays
>> enabled all the time in practice, secondly there is benefit from manually
>> disabled clock because hardware auto-gates it during idle by itself.
> 
> This assumes that the channel is allocated during a driver
> initialisation. That may not always be the case. I believe audio is one
> case where channels are requested at the start of audio playback.

At least serial, I2C, SPI and T20 FUSE are permanently keeping channels
allocated, thus audio is an exception here. I don't think that it's
practical to assume that there is a real-world use-case where audio
driver is the only active DMA client.

The benefits of gating the DMA clock are also dim, do you have any
power-consumption numbers that show that it's really worth to care about
the clock-gating?

  reply	other threads:[~2020-01-07 17:12 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-06  1:16 [PATCH v3 00/13] NVIDIA Tegra APB DMA driver fixes and improvements Dmitry Osipenko
2020-01-06  1:16 ` [PATCH v3 01/13] dmaengine: tegra-apb: Fix use-after-free Dmitry Osipenko
2020-01-06  1:16 ` [PATCH v3 02/13] dmaengine: tegra-apb: Implement synchronization callback Dmitry Osipenko
2020-01-06  1:16 ` [PATCH v3 03/13] dmaengine: tegra-apb: Prevent race conditions on channel's freeing Dmitry Osipenko
2020-01-06  1:16 ` [PATCH v3 04/13] dmaengine: tegra-apb: Clean up tasklet releasing Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 05/13] dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 06/13] dmaengine: tegra-apb: Use devm_platform_ioremap_resource Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 07/13] dmaengine: tegra-apb: Use devm_request_irq Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 08/13] dmaengine: tegra-apb: Fix coding style problems Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 09/13] dmaengine: tegra-apb: Remove runtime PM usage Dmitry Osipenko
2020-01-07 15:13   ` Jon Hunter
2020-01-07 17:12     ` Dmitry Osipenko [this message]
2020-01-07 18:38       ` Jon Hunter
2020-01-08 15:10         ` Dmitry Osipenko
2020-01-10  8:05         ` Vinod Koul
2020-01-06  1:17 ` [PATCH v3 10/13] dmaengine: tegra-apb: Clean up suspend-resume Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 11/13] dmaengine: tegra-apb: Add missing of_dma_controller_free Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 12/13] dmaengine: tegra-apb: Allow to compile as a loadable kernel module Dmitry Osipenko
2020-01-06  1:17 ` [PATCH v3 13/13] dmaengine: tegra-apb: Remove MODULE_ALIAS Dmitry Osipenko
2020-01-08 12:51 ` [PATCH v3 00/13] NVIDIA Tegra APB DMA driver fixes and improvements Thierry Reding
2020-01-08 15:07   ` Dmitry Osipenko
2020-01-09 10:04     ` Thierry Reding
2020-01-09 14:24       ` Dmitry Osipenko

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