From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Huang Shijie <b32955@freescale.com>
Cc: marex@denx.de, Huang Shijie <shijie8@gmail.com>,
Vinod Koul <vinod.koul@linux.intel.com>,
shawn.guo@linaro.org, alsa-devel@alsa-project.org, tiwai@suse.de,
artem.bityutskiy@linux.intel.com,
broonie@opensource.wolfsonmicro.com, linux-mmc@vger.kernel.org,
w.sang@pengutronix.de, perex@perex.cz,
linux-mtd@lists.infradead.org, linux-i2c@vger.kernel.org,
ben-linux@fluff.org, djbw@fb.com, khali@linux-fr.org,
cjb@laptop.org, dwmw2@infradead.org, lrg@ti.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] dma: add new DMA control commands
Date: Thu, 18 Oct 2012 09:52:08 +0100 [thread overview]
Message-ID: <20121018085208.GR21164@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <507FA595.4020507@freescale.com>
On Thu, Oct 18, 2012 at 02:45:41PM +0800, Huang Shijie wrote:
> 于 2012年10月18日 14:18, Vinod Koul 写道:
>> Why cant you do start (prepare clock etc) when you submit the descriptor
>> to dmaengine. Can be done in tx_submit callback.
>> Similarly remove the clock when dma transaction gets completed.
> I ever thought this method too.
>
> But it will become low efficient in the following case:
>
> Assuming the gpmi-nand driver has to read out 1024 pages in one
> _SINGLE_ read operation.
> The gpmi-nand will submit the descriptor to dmaengine per page. So with
> your method,
> the system will repeat the enable/disable dma clock 1024 time. At every
> enable/disable dma clock,
> the system has to enable the clock chain and it's parents ...
And what if you stop using clk_prepare_enable(), and prepare the clock
when the channel is requested and only use clk_enable() in the tx_submit
method?
next prev parent reply other threads:[~2012-10-18 9:03 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-18 5:32 [PATCH] dma: add new DMA control commands Huang Shijie
2012-10-18 6:18 ` Vinod Koul
2012-10-18 6:45 ` Huang Shijie
2012-10-18 7:14 ` Marek Vasut
2012-10-18 7:49 ` Huang Shijie
2012-10-18 8:16 ` Marek Vasut
2012-10-18 8:29 ` Huang Shijie
2012-11-09 15:29 ` Artem Bityutskiy
2012-10-18 8:49 ` Huang Shijie
2012-10-18 8:49 ` Marek Vasut
2012-10-18 9:13 ` Huang Shijie
2012-10-18 10:51 ` Marek Vasut
2012-10-18 15:11 ` Huang Shijie
2012-10-18 8:52 ` Russell King - ARM Linux [this message]
2012-10-18 9:10 ` Huang Shijie
2012-10-18 9:29 ` Jassi Brar
2012-10-18 15:18 ` Huang Shijie
2012-10-18 15:25 ` Jassi Brar
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