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Date: Fri, 18 Oct 2013 09:36:06 +0530
From: Sourav Poddar <sourav.poddar@ti.com>
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To: Mark Brown <broonie@kernel.org>
Subject: Re: [PATCH 1/3] spi/qspi: Add memory mapped read support.
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Cc: Peter Korsgaard <peter@korsgaard.com>,
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 "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>, "Gupta,
 Pekon" <pekon@ti.com>, "spi-devel-general@lists.sourceforge.net"
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On Friday 18 October 2013 05:12 AM, Mark Brown wrote:
> On Thu, Oct 17, 2013 at 01:03:26PM +0000, Gupta, Pekon wrote:
>
>> mtd_read() {
>> 	if (flash->mmap_mode)
>> 		if (dma_available)
>> 			read_via_dma(destination, source, length);
>> 		else
>> 			memcpy(destination, source, length);
>> 	else
>> 		/* use spi frame-work by default */
>> }
>> Are you looking for comparison between  read_via_dma() v/s memcpy() ?
> No, I'm looking for a comparison of normal SPI mode (which I'd have
> expected to DMA) and the memcpy() mode.
>
>> If yes, then unfortunately we are bit constrained because our controller
>> does not support DMA. So, we have to depend on CPU based memcpy()
>> only. However, use of DMA can be added as an independent patch on
>> top of this CASE-2 patch.
> However if the controller can't DMA at all then that's not going to be
> possible...  am I understanding you correctly that normal SPI can't DMA?
Yes, you are correct, the normal SPI cant DMA.