From: Vinod Koul <vinod.koul@intel.com>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-omap@vger.kernel.org, linux@arm.linux.org.uk,
misael.lopez@ti.com
Subject: Re: [PATCH] dmaengine: omap-dma: Enable packed accesses for cyclic transfers
Date: Mon, 5 Oct 2015 16:32:58 +0100 [thread overview]
Message-ID: <20151005153258.GF13501@vkoul-mobl.iind.intel.com> (raw)
In-Reply-To: <1442233865-10412-1-git-send-email-peter.ujfalusi@ti.com>
On Mon, Sep 14, 2015 at 03:31:05PM +0300, Peter Ujfalusi wrote:
> From: Misael Lopez Cruz <misael.lopez@ti.com>
>
> The L3 throughput can be higher than expected when packed access
> is not enabled. The ratio depends on the number of bytes in a
> transaction and the EMIF interface width.
>
> The throughput was measured for the following settings/cases:
>
> * Case 1: Burst size of 64 bytes, packed access disabled
> * Case 2: Burst size of 64 bytes, packed access enabled
> * Case 3: Burst disabled, packed access disabled
>
> Throughput measurements were done during McASP-based audio
> playback on the Jacinto6 EVM using the omapconf tool [1]:
> $ omapconf trace bw -m sdma_rd
>
> ---------------------------------------------------------
> Throughput (MB/s)
> Audio parameters Case 1 Case 2 Case 3
> ---------------------------------------------------------
> 44.1kHz, 16-bits, stereo 1.41 0.18 1.41
> 44.1kHz, 32-bits, stereo 1.41 0.35 1.41
> 44.1kHz, 16-bits, 4-chan 2.82 0.35 2.82
> 44.1kHz, 16-bits, 6-chan 4.23 0.53 4.23
> 44.1kHz, 16-bits, 8-chan 5.64 0.71 5.64
> ---------------------------------------------------------
>
> From above measurements, case 2 is the only one that delivers
> the expected throughput for the given audio parameters. For
> that reason, the packed accesses are now enabled.
>
> It's worth to mention that packed accesses cannot be enabled
> for all addressing modes. In cyclic transfers, it can be
> enabled in the source for MEM_TO_DEV and in dest for DEV_TO_MEM,
> as they use post-increment mode which supports packed accesses.
>
> Peter Ujfalusi:
> From the TRM regarding to this:
> "NOTE: Except in the constant addressing mode, the source or
> destination must be specified as packed for burst transactions
> to occur."
>
> So w/o the packed setting the burst on the MEM side was not
> enabled, this explains the numbers.
>
> [1] https://github.com/omapconf/omapconf
>
Applied, thanks
--
~Vinod
prev parent reply other threads:[~2015-10-05 15:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-14 12:31 [PATCH] dmaengine: omap-dma: Enable packed accesses for cyclic transfers Peter Ujfalusi
2015-09-14 12:31 ` Peter Ujfalusi
2015-09-25 7:00 ` Peter Ujfalusi
2015-09-25 7:00 ` Peter Ujfalusi
2015-10-05 15:32 ` Vinod Koul [this message]
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