linux-kernel - Re: [PATCH v4 0/6] dma: edma: Support scatter-lists of any length

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Date:	Mon, 02 Sep 2013 17:29:53 +0530
From:	Vinod Koul <vkoul@...radead.org>
To:	Joel Fernandes <joelf@...com>
Cc:	vinod.koul@...el.com, Sekhar Nori <nsekhar@...com>,
	Matt Porter <matt@...orter.com>,
	Russell King <linux@....linux.org.uk>,
	Sricharan R <r.sricharan@...com>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Koen Kooi <koen@...inion.thruhere.net>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Franklin Cooper <fcooper@...com>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 0/6] dma: edma: Support scatter-lists of any length

On Thu, 2013-08-29 at 18:05 -0500, Joel Fernandes wrote:
> The following series adds support to EDMA driver to enable DMA of
> scatter-gather lists of arbitrary length, but still make use of only
> a certain MAX number of slots at a time for a given channel. Thus
> free-ing up the rest of the slots to other slaves/channels.  With this
> there is no need for slave drivers to query the EDMA driver about how
> much is the MAX it can send at a time as done in [1]. Drivers can send
> SG lists of any number of entries to DMA. Reference discussion at [2].
> 
> With this, all the patches for MMC and EDMA related to "sg limits" can be
> dropped.
> 
> Tested omap-aes and omap_hsmmc drivers with different MAX number of slots,
> even just 1. In the case where it is 1, only 1-slot is used to DMA an
> entire scatter list of arbitrary length.
> Since this series touches EDMA private API code also shared with davinci-pcm,
> playback of a 16-bit 44.1KHz audio file with davinci-pcm has been tested.
> 
> Sample test run with 1 vs 16 (MAX number of slots/SG) in omap-aes driver:
> MAX slots = 1:
>  (128 bit key, 8192 byte blocks): 1266 operations in 1 seconds (10371072 bytes)
> MAX slots = 16:
>  (128 bit key, 8192 byte blocks): 1601 operations in 1 seconds (13115392 bytes)
> 
> Note: For the above test, 8K buffer is mapped into SG list of size 2 so
> only 2 slots are required. So beyond size 2, there will not be any noticeable
> performance improvement. But above experiment just shows as proof of concept
> that even using 1 slot is managed by just DMA'ing 1 SG entry at a time.
much better series, thanks

I think i am okay with this, if anyone has objections pls speak up. Also
I need ack on the ARM patch 3/6 before I can carry this.

-- 
Vinod Koul
Intel Corp.

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